[hibernate-commits] Hibernate SVN: r15830 - core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content.

Author: steve.ebersole(a)jboss.com Date: 2009-01-29 14:56:06 -0500 (Thu, 29 Jan 2009) New Revision: 15830 Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/architecture.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/association_mapping.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/basic_mapping.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/batch.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/best_practices.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/collection_mapping.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/component_mapping.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/configuration.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/events.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_mappings.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_parentchild.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_weblog.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/filters.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/inheritance_mapping.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/performance.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/persistent_classes.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/preface.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_criteria.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_hql.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_sql.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/session_api.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/toolset_guide.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/transactions.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/tutorial.xml core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/xml.xml Log: HHH-3742 : doc corrections Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/architecture.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/architecture.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/architecture.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -33,7 +33,7 @@ <title>Overview</title> <para> - A (very) high-level view of the Hibernate architecture: + The diagram below provides a high-level view of the Hibernate architecture: </para> <mediaobject> @@ -45,15 +45,21 @@ </imageobject> </mediaobject> + + <para> - This diagram shows Hibernate using the database and configuration data to - provide persistence services (and persistent objects) to the application. + We do not have the scope in this document to provide a more detailed view of all the runtime architectures available; + Hibernate is flexible and supports several different approaches. We will, however, + show the two extremes: "minimal" architecture and "comprehensive" architecture. + </para> + + <para> + This next diagram illustrates how Hibernate utilizes database and configuration data to + provide persistence services, and persistent objects, to the application. </para> - <para> - We would like to show a more detailed view of the runtime architecture. - Unfortunately, Hibernate is flexible and supports several approaches. We will - show the two extremes. The "lite" architecture has the application + <para> + The "minimal" architecture has the application provide its own JDBC connections and manage its own transactions. This approach uses a minimal subset of Hibernate's APIs: </para> @@ -67,9 +73,11 @@ </imageobject> </mediaobject> - <para> - The "full cream" architecture abstracts the application away from the - underlying JDBC/JTA APIs and lets Hibernate take care of the details. + + + <para> + The "comprehensive" architecture abstracts the application away from the + underlying JDBC/JTA APIs and allows Hibernate to manage the details. </para> <mediaobject> @@ -82,18 +90,18 @@ </mediaobject> <para> - Heres some definitions of the objects in the diagrams: + Here are some definitions of the objects depicted in the diagrams: <variablelist spacing="compact"> <varlistentry> <term>SessionFactory (<literal>org.hibernate.SessionFactory</literal>)</term> <listitem> <para> - A threadsafe (immutable) cache of compiled mappings for a single database. + A threadsafe, immutable cache of compiled mappings for a single database. A factory for <literal>Session</literal> and a client of - <literal>ConnectionProvider</literal>. Might hold an optional (second-level) - cache of data that is reusable between transactions, at a - process- or cluster-level. + <literal>ConnectionProvider</literal>, <literal>SessionFactory</literal> can hold an optional (second-level) + cache of data that is reusable between transactions at a + process, or cluster, level. </para> </listitem> </varlistentry> @@ -102,9 +110,9 @@ <listitem> <para> A single-threaded, short-lived object representing a conversation between - the application and the persistent store. Wraps a JDBC connection. Factory - for <literal>Transaction</literal>. Holds a mandatory (first-level) cache - of persistent objects, used when navigating the object graph or looking up + the application and the persistent store. It wraps a JDBC connection and is a factory + for <literal>Transaction</literal>. <literal>Session</literal> holds a mandatory first-level cache + of persistent objects that are used when navigating the object graph or looking up objects by identifier. </para> </listitem> @@ -114,10 +122,9 @@ <listitem> <para> Short-lived, single threaded objects containing persistent state and business - function. These might be ordinary JavaBeans/POJOs, the only special thing about - them is that they are currently associated with (exactly one) - <literal>Session</literal>. As soon as the <literal>Session</literal> is closed, - they will be detached and free to use in any application layer (e.g. directly + function. These can be ordinary JavaBeans/POJOs. They are associated with exactly one + <literal>Session</literal>. Once the <literal>Session</literal> is closed, + they will be detached and free to use in any application layer (for example, directly as data transfer objects to and from presentation). </para> </listitem> @@ -128,7 +135,7 @@ <para> Instances of persistent classes that are not currently associated with a <literal>Session</literal>. They may have been instantiated by - the application and not (yet) persisted or they may have been instantiated by a + the application and not yet persisted, or they may have been instantiated by a closed <literal>Session</literal>. </para> </listitem> @@ -138,11 +145,11 @@ <listitem> <para> (Optional) A single-threaded, short-lived object used by the application to - specify atomic units of work. Abstracts application from underlying JDBC, + specify atomic units of work. It abstracts the application from the underlying JDBC, JTA or CORBA transaction. A <literal>Session</literal> might span several <literal>Transaction</literal>s in some cases. However, transaction demarcation, either using the underlying API or <literal>Transaction</literal>, is never - optional! + optional. </para> </listitem> </varlistentry> @@ -150,9 +157,9 @@ <term>ConnectionProvider (<literal>org.hibernate.connection.ConnectionProvider</literal>)</term> <listitem> <para> - (Optional) A factory for (and pool of) JDBC connections. Abstracts application from + (Optional) A factory for, and pool of, JDBC connections. It abstracts the application from underlying <literal>Datasource</literal> or <literal>DriverManager</literal>. - Not exposed to application, but can be extended/implemented by the developer. + It is not exposed to application, but it can be extended and/or implemented by the developer. </para> </listitem> </varlistentry> @@ -160,8 +167,8 @@ <term>TransactionFactory (<literal>org.hibernate.TransactionFactory</literal>)</term> <listitem> <para> - (Optional) A factory for <literal>Transaction</literal> instances. Not exposed to the - application, but can be extended/implemented by the developer. + (Optional) A factory for <literal>Transaction</literal> instances. It is not exposed to the + application, but it can be extended and/or implemented by the developer. </para> </listitem> </varlistentry> @@ -169,7 +176,7 @@ <term><emphasis>Extension Interfaces</emphasis></term> <listitem> <para> - Hibernate offers many optional extension interfaces you can implement to customize + Hibernate offers a range of optional extension interfaces you can implement to customize the behavior of your persistence layer. See the API documentation for details. </para> </listitem> @@ -178,18 +185,18 @@ </para> <para> - Given a "lite" architecture, the application bypasses the + Given a "minimal" architecture, the application bypasses the <literal>Transaction</literal>/<literal>TransactionFactory</literal> and/or - <literal>ConnectionProvider</literal> APIs to talk to JTA or JDBC directly. + <literal>ConnectionProvider</literal> APIs to communicate with JTA or JDBC directly. </para> </sect1> <sect1 id="architecture-states" revision="1"> <title>Instance states</title> <para> - An instance of a persistent classes may be in one of three different states, - which are defined with respect to a <emphasis>persistence context</emphasis>. - The Hibernate <literal>Session</literal> object is the persistence context: + An instance of a persistent class can be in one of three different states. These states are + defined in relation to a <emphasis>persistence context</emphasis>. + The Hibernate <literal>Session</literal> object is the persistence context. The three different states are as follows: </para> <variablelist spacing="compact"> @@ -197,9 +204,9 @@ <term>transient</term> <listitem> <para> - The instance is not, and has never been associated with - any persistence context. It has no persistent identity - (primary key value). + The instance is not associated with + any persistence context. It has no persistent identity or + primary key value. </para> </listitem> </varlistentry> @@ -209,11 +216,11 @@ <para> The instance is currently associated with a persistence context. It has a persistent identity (primary key value) - and, perhaps, a corresponding row in the database. For a + and can have a corresponding row in the database. For a particular persistence context, Hibernate <emphasis>guarantees</emphasis> that persistent identity - is equivalent to Java identity (in-memory location of the - object). + is equivalent to Java identity in relation to the in-memory location of the + object. </para> </listitem> </varlistentry> @@ -224,9 +231,9 @@ The instance was once associated with a persistence context, but that context was closed, or the instance was serialized to another process. It has a persistent - identity and, perhaps, a corresponding row in the database. - For detached instances, Hibernate makes no guarantees - about the relationship between persistent identity and + identity and can have a corresponding row in the database. + For detached instances, Hibernate does not guarantee + the relationship between persistent identity and Java identity. </para> </listitem> @@ -238,36 +245,36 @@ <title>JMX Integration</title> <para> - JMX is the J2EE standard for management of Java components. Hibernate may be managed via - a JMX standard service. We provide an MBean implementation in the distribution, + JMX is the J2EE standard for the management of Java components. Hibernate can be managed via + a JMX standard service. AN MBean implementation is provided in the distribution: <literal>org.hibernate.jmx.HibernateService</literal>. </para> <para> - For an example how to deploy Hibernate as a JMX service on the JBoss Application Server, - please see the JBoss User Guide. On JBoss AS, you also get these benefits if you deploy + For an example of how to deploy Hibernate as a JMX service on the JBoss Application Server, + please see the JBoss User Guide. JBoss AS also provides these benefits if you deploy using JMX: </para> <itemizedlist> <listitem> <para> - <emphasis>Session Management:</emphasis> The Hibernate <literal>Session</literal>'s life cycle - can be automatically bound to the scope of a JTA transaction. This means you no - longer have to manually open and close the <literal>Session</literal>, this - becomes the job of a JBoss EJB interceptor. You also don't have to worry about - transaction demarcation in your code anymore (unless you'd like to write a portable - persistence layer of course, use the optional Hibernate <literal>Transaction</literal> + <emphasis>Session Management</emphasis>: the Hibernate <literal>Session</literal>'s life cycle + can be automatically bound to the scope of a JTA transaction. This means that you no + longer have to manually open and close the <literal>Session</literal>; this + becomes the job of a JBoss EJB interceptor. You also do not have to worry about + transaction demarcation in your code (if you would like to write a portable + persistence layer use the optional Hibernate <literal>Transaction</literal> API for this). You call the <literal>HibernateContext</literal> to access a <literal>Session</literal>. </para> </listitem> <listitem> <para> - <emphasis>HAR deployment:</emphasis> Usually you deploy the Hibernate JMX service using a JBoss - service deployment descriptor (in an EAR and/or SAR file), it supports all the usual + <emphasis>HAR deployment</emphasis>: the Hibernate JMX service is deployed using a JBoss + service deployment descriptor in an EAR and/or SAR file, as it supports all the usual configuration options of a Hibernate <literal>SessionFactory</literal>. However, you still - have to name all your mapping files in the deployment descriptor. If you decide to use + need to name all your mapping files in the deployment descriptor. If you use the optional HAR deployment, JBoss will automatically detect all mapping files in your HAR file. </para> @@ -279,45 +286,45 @@ </para> <para> - Another feature available as a JMX service are runtime Hibernate statistics. See - <xref linkend="configuration-optional-statistics"/>. + Another feature available as a JMX service is runtime Hibernate statistics. See + <xref linkend="configuration-optional-statistics"/> for more information. </para> </sect1> <sect1 id="architecture-jca" revision="1"> <title>JCA Support</title> <para> - Hibernate may also be configured as a JCA connector. Please see the website for more - details. Please note that Hibernate JCA support is still considered experimental. + Hibernate can also be configured as a JCA connector. Please see the website for more + information. Please note, however, that at this stage Hibernate JCA support is under development. </para> </sect1> <sect1 id="architecture-current-session" revision="2"> - <title>Contextual Sessions</title> + <title>Contextual sessions</title> <para> - Most applications using Hibernate need some form of "contextual" sessions, where a given + Most applications using Hibernate need some form of "contextual" session, where a given session is in effect throughout the scope of a given context. However, across applications - the definition of what constitutes a context is typically different; and different contexts + the definition of what constitutes a context is typically different; different contexts define different scopes to the notion of current. Applications using Hibernate prior to version 3.0 tended to utilize either home-grown <literal>ThreadLocal</literal>-based contextual sessions, helper classes such as <literal>HibernateUtil</literal>, or utilized - third-party frameworks (such as Spring or Pico) which provided proxy/interception-based contextual sessions. + third-party frameworks, such as Spring or Pico, which provided proxy/interception-based contextual sessions. </para> <para> Starting with version 3.0.1, Hibernate added the <literal>SessionFactory.getCurrentSession()</literal> - method. Initially, this assumed usage of <literal>JTA</literal> transactions, where the + method. Initially, this assumed usage of <literal>JTA</literal> transactions, where the <literal>JTA</literal> transaction defined both the scope and context of a current session. - The Hibernate team maintains that, given the maturity of the numerous stand-alone - <literal>JTA TransactionManager</literal> implementations out there, most (if not all) - applications should be using <literal>JTA</literal> transaction management whether or not + Given the maturity of the numerous stand-alone + <literal>JTA TransactionManager</literal> implementations, most, if not all, + applications should be using <literal>JTA</literal> transaction management, whether or not they are deployed into a <literal>J2EE</literal> container. Based on that, the - <literal>JTA</literal>-based contextual sessions is all you should ever need to use. + <literal>JTA</literal>-based contextual sessions are all you need to use. </para> <para> However, as of version 3.1, the processing behind <literal>SessionFactory.getCurrentSession()</literal> is now pluggable. To that - end, a new extension interface (<literal>org.hibernate.context.CurrentSessionContext</literal>) - and a new configuration parameter (<literal>hibernate.current_session_context_class</literal>) + end, a new extension interface, <literal>org.hibernate.context.CurrentSessionContext</literal>, + and a new configuration parameter, <literal>hibernate.current_session_context_class</literal>, have been added to allow pluggability of the scope and context of defining current sessions. </para> <para> @@ -325,13 +332,13 @@ interface for a detailed discussion of its contract. It defines a single method, <literal>currentSession()</literal>, by which the implementation is responsible for tracking the current contextual session. Out-of-the-box, Hibernate comes with three - implementations of this interface. + implementations of this interface: </para> <itemizedlist> <listitem> <para> - <literal>org.hibernate.context.JTASessionContext</literal> - current sessions + <literal>org.hibernate.context.JTASessionContext</literal>: current sessions are tracked and scoped by a <literal>JTA</literal> transaction. The processing here is exactly the same as in the older JTA-only approach. See the Javadocs for details. @@ -339,41 +346,41 @@ </listitem> <listitem> <para> - <literal>org.hibernate.context.ThreadLocalSessionContext</literal> - current - sessions are tracked by thread of execution. Again, see the Javadocs for details. + <literal>org.hibernate.context.ThreadLocalSessionContext</literal>:current + sessions are tracked by thread of execution. See the Javadocs for details. </para> </listitem> <listitem> <para> - <literal>org.hibernate.context.ManagedSessionContext</literal> - current + <literal>org.hibernate.context.ManagedSessionContext</literal>: current sessions are tracked by thread of execution. However, you are responsible to bind and unbind a <literal>Session</literal> instance with static methods - on this class, it does never open, flush, or close a <literal>Session</literal>. + on this class: it does not open, flush, or close a <literal>Session</literal>. </para> </listitem> </itemizedlist> <para> The first two implementations provide a "one session - one database transaction" programming - model, also known and used as <emphasis>session-per-request</emphasis>. The beginning + model. This is also also known and used as <emphasis>session-per-request</emphasis>. The beginning and end of a Hibernate session is defined by the duration of a database transaction. If you use programmatic transaction demarcation in plain JSE without JTA, you are advised to use the Hibernate <literal>Transaction</literal> API to hide the underlying transaction system - from your code. If you use JTA, use the JTA interfaces to demarcate transactions. If you + from your code. If you use JTA, you can utilize the JTA interfaces to demarcate transactions. If you execute in an EJB container that supports CMT, transaction boundaries are defined declaratively - and you don't need any transaction or session demarcation operations in your code. + and you do not need any transaction or session demarcation operations in your code. Refer to <xref linkend="transactions"/> for more information and code examples. </para> <para> The <literal>hibernate.current_session_context_class</literal> configuration parameter defines which <literal>org.hibernate.context.CurrentSessionContext</literal> implementation - should be used. Note that for backwards compatibility, if this config param is not set + should be used. For backwards compatibility, if this configuration parameter is not set but a <literal>org.hibernate.transaction.TransactionManagerLookup</literal> is configured, Hibernate will use the <literal>org.hibernate.context.JTASessionContext</literal>. Typically, the value of this parameter would just name the implementation class to - use; for the three out-of-the-box implementations, however, there are three corresponding - short names, "jta", "thread", and "managed". + use. For the three out-of-the-box implementations, however, there are three corresponding + short names: "jta", "thread", and "managed". </para> </sect1> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/association_mapping.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/association_mapping.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/association_mapping.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -33,22 +33,22 @@ <title>Introduction</title> <para> - Association mappings are the often most difficult thing to get right. In - this section we'll go through the canonical cases one by one, starting - with unidirectional mappings, and then considering the bidirectional cases. - We'll use <literal>Person</literal> and <literal>Address</literal> in all + Association mappings are often the most difficult thing to implement correctly. In + this section we examine some canonical cases one by one, starting + with unidirectional mappings and then bidirectional cases. + We will use <literal>Person</literal> and <literal>Address</literal> in all the examples. </para> <para> - We'll classify associations by whether or not they map to an intervening - join table, and by multiplicity. + Associations will be classified by multiplicity and whether or not they map to an intervening + join table. </para> <para> - Nullable foreign keys are not considered good practice in traditional data - modelling, so all our examples use not null foreign keys. This is not a - requirement of Hibernate, and the mappings will all work if you drop the + Nullable foreign keys are not considered to be good practice in traditional data + modelling, so our examples do not use nullable foreign keys. This is not a + requirement of Hibernate, and the mappings will work if you drop the nullability constraints. </para> @@ -58,7 +58,7 @@ <title>Unidirectional associations</title> <sect2 id="assoc-unidirectional-m21"> - <title>many to one</title> + <title>Many-to-one</title> <para> A <emphasis>unidirectional many-to-one association</emphasis> is the most @@ -87,7 +87,7 @@ </sect2> <sect2 id="assoc-unidirectional-121"> - <title>one to one</title> + <title>One-to-one</title> <para> A <emphasis>unidirectional one-to-one association on a foreign key</emphasis> @@ -116,8 +116,8 @@ <para> A <emphasis>unidirectional one-to-one association on a primary key</emphasis> - usually uses a special id generator. (Notice that we've reversed the direction - of the association in this example.) + usually uses a special id generator In this example, however, we have reversed the direction + of the association: </para> <programlisting><![CDATA[<class name="Person"> @@ -142,11 +142,11 @@ </sect2> <sect2 id="assoc-unidirectional-12m"> - <title>one to many</title> + <title>One-to-many</title> <para> A <emphasis>unidirectional one-to-many association on a foreign key</emphasis> - is a very unusual case, and is not really recommended. + is an unusual case, and is not recommended. </para> <programlisting><![CDATA[<class name="Person"> @@ -171,7 +171,7 @@ ]]></programlisting> <para> - We think it's better to use a join table for this kind of association. + You should instead use a join table for this kind of association. </para> </sect2> @@ -182,12 +182,12 @@ <title>Unidirectional associations with join tables</title> <sect2 id="assoc-unidirectional-join-12m"> - <title>one to many</title> + <title>One-to-many</title> <para> A <emphasis>unidirectional one-to-many association on a join table</emphasis> - is much preferred. Notice that by specifying <literal>unique="true"</literal>, - we have changed the multiplicity from many-to-many to one-to-many. + is the preferred option. Specifying <literal>unique="true"</literal>, + changes the multiplicity from many-to-many to one-to-many. </para> <programlisting><![CDATA[<class name="Person"> @@ -216,11 +216,11 @@ </sect2> <sect2 id="assoc-unidirectional-join-m21"> - <title>many to one</title> + <title>Many-to-one</title> <para> A <emphasis>unidirectional many-to-one association on a join table</emphasis> - is quite common when the association is optional. + is common when the association is optional. For example: </para> <programlisting><![CDATA[<class name="Person"> @@ -250,11 +250,11 @@ </sect2> <sect2 id="assoc-unidirectional-join-121"> - <title>one to one</title> + <title>One-to-one</title> <para> - A <emphasis>unidirectional one-to-one association on a join table</emphasis> - is extremely unusual, but possible. + A <emphasis>unidirectional one-to-one association on a join table</emphasis> is possible, + but extremely unusual. </para> <programlisting><![CDATA[<class name="Person"> @@ -286,10 +286,10 @@ </sect2> <sect2 id="assoc-unidirectional-join-m2m"> - <title>many to many</title> + <title>Many-to-many</title> <para> - Finally, we have a <emphasis>unidirectional many-to-many association</emphasis>. + Finally, here is an example of a <emphasis>unidirectional many-to-many association</emphasis>. </para> <programlisting><![CDATA[<class name="Person"> @@ -322,12 +322,12 @@ <title>Bidirectional associations</title> <sect2 id="assoc-bidirectional-m21" revision="2"> - <title>one to many / many to one</title> + <title>one-to-many / many-to-one</title> <para> A <emphasis>bidirectional many-to-one association</emphasis> is the - most common kind of association. (This is the standard parent/child - relationship.) + most common kind of association. The following example illustrates the standard parent/child + relationship. </para> <programlisting><![CDATA[<class name="Person"> @@ -355,11 +355,11 @@ ]]></programlisting> <para> - If you use a <literal>List</literal> (or other indexed collection) you need - to set the <literal>key</literal> column of the foreign key to <literal>not null</literal>, - and let Hibernate manage the association from the collections side to maintain the index - of each element (making the other side virtually inverse by setting - <literal>update="false"</literal> and <literal>insert="false"</literal>): + If you use a <literal>List</literal>, or other indexed collection, + set the <literal>key</literal> column of the foreign key to <literal>not null</literal>. + Hibernate will manage the association from the collections side to maintain the index + of each element, making the other side virtually inverse by setting + <literal>update="false"</literal> and <literal>insert="false"</literal>: </para> <programlisting><![CDATA[<class name="Person"> @@ -383,9 +383,10 @@ </class>]]></programlisting> <para> - It is important that you define <literal>not-null="true"</literal> on the - <literal>&lt;key&gt;</literal> element of the collection mapping if the - underlying foreign key column is <literal>NOT NULL</literal>. Don't only + If the underlying foreign key column is <literal>NOT NULL</literal>, it + is important that you define <literal>not-null="true"</literal> on the + <literal>&lt;key&gt;</literal> element of the collection mapping. + Do not only declare <literal>not-null="true"</literal> on a possible nested <literal>&lt;column&gt;</literal> element, but on the <literal>&lt;key&gt;</literal> element. @@ -394,11 +395,11 @@ </sect2> <sect2 id="assoc-bidirectional-121"> - <title>one to one</title> + <title>One-to-one</title> <para> A <emphasis>bidirectional one-to-one association on a foreign key</emphasis> - is quite common. + is common: </para> <programlisting><![CDATA[<class name="Person"> @@ -425,7 +426,7 @@ <para> A <emphasis>bidirectional one-to-one association on a primary key</emphasis> - uses the special id generator. + uses the special id generator: </para> <programlisting><![CDATA[<class name="Person"> @@ -457,11 +458,11 @@ <title>Bidirectional associations with join tables</title> <sect2 id="assoc-bidirectional-join-12m"> - <title>one to many / many to one</title> + <title>one-to-many / many-to-one</title> <para> - A <emphasis>bidirectional one-to-many association on a join table</emphasis>. - Note that the <literal>inverse="true"</literal> can go on either end of the + The following is an example of a <emphasis>bidirectional one-to-many association on a join table</emphasis>. + The <literal>inverse="true"</literal> can go on either end of the association, on the collection, or on the join. </para> @@ -503,8 +504,8 @@ <title>one to one</title> <para> - A <emphasis>bidirectional one-to-one association on a join table</emphasis> - is extremely unusual, but possible. + A <emphasis>bidirectional one-to-one association on a join table</emphasis> is possible, + but extremely unusual. </para> <programlisting><![CDATA[<class name="Person"> @@ -546,10 +547,10 @@ </sect2> <sect2 id="assoc-bidirectional-join-m2m" revision="1"> - <title>many to many</title> + <title>Many-to-many</title> <para> - Finally, we have a <emphasis>bidirectional many-to-many association</emphasis>. + Here is an example of a <emphasis>bidirectional many-to-many association</emphasis>. </para> <programlisting><![CDATA[<class name="Person"> @@ -589,11 +590,11 @@ <para> More complex association joins are <emphasis>extremely</emphasis> rare. - Hibernate makes it possible to handle more complex situations using + Hibernate handles more complex situations by using SQL fragments embedded in the mapping document. For example, if a table with historical account information data defines <literal>accountNumber</literal>, <literal>effectiveEndDate</literal> - and <literal>effectiveStartDate</literal>columns, mapped as follows: + and <literal>effectiveStartDate</literal>columns, it would be mapped as follows: </para> <programlisting><![CDATA[<properties name="currentAccountKey"> @@ -606,8 +607,8 @@ <property name="effectiveStateDate" type="date" not-null="true"/>]]></programlisting> <para> - Then we can map an association to the <emphasis>current</emphasis> instance - (the one with null <literal>effectiveEndDate</literal>) using: + You can then map an association to the <emphasis>current</emphasis> instance, + the one with null <literal>effectiveEndDate</literal>, by using: </para> <programlisting><![CDATA[<many-to-one name="currentAccountInfo" @@ -621,8 +622,8 @@ In a more complex example, imagine that the association between <literal>Employee</literal> and <literal>Organization</literal> is maintained in an <literal>Employment</literal> table full of historical employment data. - Then an association to the employee's <emphasis>most recent</emphasis> employer - (the one with the most recent <literal>startDate</literal>) might be mapped this way: + An association to the employee's <emphasis>most recent</emphasis> employer, + the one with the most recent <literal>startDate</literal>, could be mapped in the following way: </para> <programlisting><![CDATA[<join> @@ -639,7 +640,7 @@ </join>]]></programlisting> <para> - You can get quite creative with this functionality, but it is usually more practical + This functionality allows a degree of creativity and flexibility, but it is more practical to handle these kinds of cases using HQL or a criteria query. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/basic_mapping.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/basic_mapping.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/basic_mapping.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -35,17 +35,17 @@ Object/relational mappings are usually defined in an XML document. The mapping document is designed to be readable and hand-editable. The mapping language is Java-centric, meaning that mappings are constructed around persistent class - declarations, not table declarations. + declarations and not table declarations. </para> <para> - Note that, even though many Hibernate users choose to write the XML by hand, - a number of tools exist to generate the mapping document, including XDoclet, + Please note that even though many Hibernate users choose to write the XML by hand, + a number of tools exist to generate the mapping document. These include XDoclet, Middlegen and AndroMDA. </para> <para> - Lets kick off with an example mapping: + Here is an example mapping: </para> <programlisting id="mapping-declaration-ex1" revision="1"><![CDATA[<?xml version="1.0"?> @@ -114,11 +114,11 @@ </hibernate-mapping>]]></programlisting> <para> - We will now discuss the content of the mapping document. We will only describe the + We will now discuss the content of the mapping document. We will only describe, however, the document elements and attributes that are used by Hibernate at runtime. The mapping document also contains some extra optional attributes and elements that affect the - database schemas exported by the schema export tool. (For example the <literal> - not-null</literal> attribute.) + database schemas exported by the schema export tool (for example, the <literal> + not-null</literal> attribute). </para> @@ -127,44 +127,44 @@ <title>Doctype</title> <para> - All XML mappings should declare the doctype shown. The actual DTD may be found + All XML mappings should declare the doctype shown. The actual DTD can be found at the URL above, in the directory <literal>hibernate-x.x.x/src/org/hibernate - </literal> or in <literal>hibernate3.jar</literal>. Hibernate will always look for + </literal>, or in <literal>hibernate3.jar</literal>. Hibernate will always look for the DTD in its classpath first. If you experience lookups of the DTD using an - Internet connection, check your DTD declaration against the contents of your - claspath. + Internet connection, check the DTD declaration against the contents of your + classpath. </para> <sect3 id="mapping-declaration-entity-resolution"> <title>EntityResolver</title> <para> - As mentioned previously, Hibernate will first attempt to resolve DTDs in its classpath. The - manner in which it does this is by registering a custom <literal>org.xml.sax.EntityResolver</literal> + Hibernate will first attempt to resolve DTDs in its classpath. + It does this is by registering a custom <literal>org.xml.sax.EntityResolver</literal> implementation with the SAXReader it uses to read in the xml files. This custom - <literal>EntityResolver</literal> recognizes two different systemId namespaces. + <literal>EntityResolver</literal> recognizes two different systemId namespaces: </para> <itemizedlist> <listitem> <para> a <literal>hibernate namespace</literal> is recognized whenever the - resolver encounteres a systemId starting with - <literal>http://hibernate.sourceforge.net/</literal>; the resolver - attempts to resolve these entities via the classlaoder which loaded + resolver encounters a systemId starting with + <literal>http://hibernate.sourceforge.net/</literal>;. The resolver + attempts to resolve these entities via the classloader which loaded the Hibernate classes. </para> </listitem> <listitem> <para> a <literal>user namespace</literal> is recognized whenever the - resolver encounteres a systemId using a <literal>classpath://</literal> - URL protocol; the resolver will attempt to resolve these entities + resolver encounters a systemId using a <literal>classpath://</literal> + URL protocol. The resolver will attempt to resolve these entities via (1) the current thread context classloader and (2) the classloader which loaded the Hibernate classes. </para> </listitem> </itemizedlist> <para> - An example of utilizing user namespacing: + The following is an example of utilizing user namespacing: </para> <programlisting><![CDATA[<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC @@ -189,17 +189,17 @@ </sect2> <sect2 id="mapping-declaration-mapping" revision="3"> - <title>hibernate-mapping</title> + <title>Hibernate-mapping</title> <para> This element has several optional attributes. The <literal>schema</literal> and <literal>catalog</literal> attributes specify that tables referred to in this mapping - belong to the named schema and/or catalog. If specified, tablenames will be qualified - by the given schema and catalog names. If missing, tablenames will be unqualified. + belong to the named schema and/or catalog. If they are specified, tablenames will be qualified + by the given schema and catalog names. If they are missing, tablenames will be unqualified. The <literal>default-cascade</literal> attribute specifies what cascade style - should be assumed for properties and collections which do not specify a - <literal>cascade</literal> attribute. The <literal>auto-import</literal> attribute lets us - use unqualified class names in the query language, by default. + should be assumed for properties and collections that do not specify a + <literal>cascade</literal> attribute. By default, the <literal>auto-import</literal> attribute allows you + to use unqualified class names in the query language. </para> <programlistingco> @@ -224,44 +224,44 @@ <calloutlist> <callout arearefs="hm1"> <para> - <literal>schema</literal> (optional): The name of a database schema. + <literal>schema</literal> (optional): the name of a database schema. </para> </callout> <callout arearefs="hm2"> <para> - <literal>catalog</literal> (optional): The name of a database catalog. + <literal>catalog</literal> (optional): the name of a database catalog. </para> </callout> <callout arearefs="hm3"> <para> <literal>default-cascade</literal> (optional - defaults to <literal>none</literal>): - A default cascade style. + a default cascade style. </para> </callout> <callout arearefs="hm4"> <para> <literal>default-access</literal> (optional - defaults to <literal>property</literal>): - The strategy Hibernate should use for accessing all properties. Can be a custom + the strategy Hibernate should use for accessing all properties. It can be a custom implementation of <literal>PropertyAccessor</literal>. </para> </callout> <callout arearefs="hm5"> <para> <literal>default-lazy</literal> (optional - defaults to <literal>true</literal>): - The default value for unspecifed <literal>lazy</literal> attributes of class and + the default value for unspecified <literal>lazy</literal> attributes of class and collection mappings. </para> </callout> <callout arearefs="hm6"> <para> <literal>auto-import</literal> (optional - defaults to <literal>true</literal>): - Specifies whether we can use unqualified class names (of classes in this mapping) + specifies whether we can use unqualified class names of classes in this mapping in the query language. </para> </callout> <callout arearefs="hm7"> <para> - <literal>package</literal> (optional): Specifies a package prefix to assume for + <literal>package</literal> (optional): specifies a package prefix to use for unqualified class names in the mapping document. </para> </callout> @@ -269,17 +269,17 @@ </programlistingco> <para> - If you have two persistent classes with the same (unqualified) name, you should set - <literal>auto-import="false"</literal>. Hibernate will throw an exception if you attempt + If you have two persistent classes with the same unqualified name, you should set + <literal>auto-import="false"</literal>. An exception will result if you attempt to assign two classes to the same "imported" name. </para> <para> - Note that the <literal>hibernate-mapping</literal> element allows you to nest + The <literal>hibernate-mapping</literal> element allows you to nest several persistent <literal>&lt;class&gt;</literal> mappings, as shown above. - It is however good practice (and expected by some tools) to map only a single - persistent class (or a single class hierarchy) in one mapping file and name - it after the persistent superclass, e.g. <literal>Cat.hbm.xml</literal>, + It is, however, good practice (and expected by some tools) to map only a single + persistent class, or a single class hierarchy, in one mapping file and name + it after the persistent superclass. For example, <literal>Cat.hbm.xml</literal>, <literal>Dog.hbm.xml</literal>, or if using inheritance, <literal>Animal.hbm.xml</literal>. </para> @@ -287,10 +287,10 @@ </sect2> <sect2 id="mapping-declaration-class" revision="3"> - <title>class</title> + <title>Class</title> <para> - You may declare a persistent class using the <literal>class</literal> element: + You can declare a persistent class using the <literal>class</literal> element. For example: </para> <programlistingco> @@ -344,112 +344,112 @@ <calloutlist> <callout arearefs="class1"> <para> - <literal>name</literal> (optional): The fully qualified Java class name of the - persistent class (or interface). If this attribute is missing, it is assumed + <literal>name</literal> (optional): the fully qualified Java class name of the + persistent class or interface. If this attribute is missing, it is assumed that the mapping is for a non-POJO entity. </para> </callout> <callout arearefs="class2"> <para> - <literal>table</literal> (optional - defaults to the unqualified class name): The + <literal>table</literal> (optional - defaults to the unqualified class name): the name of its database table. </para> </callout> <callout arearefs="class3"> <para> - <literal>discriminator-value</literal> (optional - defaults to the class name): A value - that distiguishes individual subclasses, used for polymorphic behaviour. Acceptable + <literal>discriminator-value</literal> (optional - defaults to the class name): a value + that distinguishes individual subclasses that is used for polymorphic behavior. Acceptable values include <literal>null</literal> and <literal>not null</literal>. </para> </callout> <callout arearefs="class4"> <para> - <literal>mutable</literal> (optional, defaults to <literal>true</literal>): Specifies + <literal>mutable</literal> (optional - defaults to <literal>true</literal>): specifies that instances of the class are (not) mutable. </para> </callout> <callout arearefs="class5"> <para> - <literal>schema</literal> (optional): Override the schema name specified by + <literal>schema</literal> (optional): overrides the schema name specified by the root <literal>&lt;hibernate-mapping&gt;</literal> element. </para> </callout> <callout arearefs="class6"> <para> - <literal>catalog</literal> (optional): Override the catalog name specified by + <literal>catalog</literal> (optional): overrides the catalog name specified by the root <literal>&lt;hibernate-mapping&gt;</literal> element. </para> </callout> <callout arearefs="class7"> <para> - <literal>proxy</literal> (optional): Specifies an interface to use for lazy - initializing proxies. You may specify the name of the class itself. + <literal>proxy</literal> (optional): specifies an interface to use for lazy + initializing proxies. You can specify the name of the class itself. </para> </callout> <callout arearefs="class8"> <para> - <literal>dynamic-update</literal> (optional, defaults to <literal>false</literal>): - Specifies that <literal>UPDATE</literal> SQL should be generated at runtime and - contain only those columns whose values have changed. + <literal>dynamic-update</literal> (optional - defaults to <literal>false</literal>): + specifies that <literal>UPDATE</literal> SQL should be generated at runtime and + can contain only those columns whose values have changed. </para> </callout> <callout arearefs="class9"> <para> - <literal>dynamic-insert</literal> (optional, defaults to <literal>false</literal>): - Specifies that <literal>INSERT</literal> SQL should be generated at runtime and + <literal>dynamic-insert</literal> (optional - defaults to <literal>false</literal>): + specifies that <literal>INSERT</literal> SQL should be generated at runtime and contain only the columns whose values are not null. </para> </callout> <callout arearefs="class10"> <para> - <literal>select-before-update</literal> (optional, defaults to <literal>false</literal>): - Specifies that Hibernate should <emphasis>never</emphasis> perform an SQL <literal>UPDATE</literal> - unless it is certain that an object is actually modified. In certain cases (actually, only - when a transient object has been associated with a new session using <literal>update()</literal>), - this means that Hibernate will perform an extra SQL <literal>SELECT</literal> to determine + <literal>select-before-update</literal> (optional - defaults to <literal>false</literal>): + specifies that Hibernate should <emphasis>never</emphasis> perform an SQL <literal>UPDATE</literal> + unless it is certain that an object is actually modified. Only + when a transient object has been associated with a new session using <literal>update()</literal>, + will Hibernate perform an extra SQL <literal>SELECT</literal> to determine if an <literal>UPDATE</literal> is actually required. </para> </callout> <callout arearefs="class11"> <para> - <literal>polymorphism</literal> (optional, defaults to <literal>implicit</literal>): - Determines whether implicit or explicit query polymorphism is used. + <literal>polymorphism</literal> (optional - defaults to <literal>implicit</literal>): + determines whether implicit or explicit query polymorphism is used. </para> </callout> <callout arearefs="class12"> <para> - <literal>where</literal> (optional) specify an arbitrary SQL <literal>WHERE</literal> - condition to be used when retrieving objects of this class + <literal>where</literal> (optional): specifies an arbitrary SQL <literal>WHERE</literal> + condition to be used when retrieving objects of this class. </para> </callout> <callout arearefs="class13"> <para> - <literal>persister</literal> (optional): Specifies a custom <literal>ClassPersister</literal>. + <literal>persister</literal> (optional): specifies a custom <literal>ClassPersister</literal>. </para> </callout> <callout arearefs="class14"> <para> - <literal>batch-size</literal> (optional, defaults to <literal>1</literal>) specify a "batch size" + <literal>batch-size</literal> (optional - defaults to <literal>1</literal>): specifies a "batch size" for fetching instances of this class by identifier. </para> </callout> <callout arearefs="class15"> <para> - <literal>optimistic-lock</literal> (optional, defaults to <literal>version</literal>): - Determines the optimistic locking strategy. + <literal>optimistic-lock</literal> (optional - defaults to <literal>version</literal>): + determines the optimistic locking strategy. </para> </callout> <callout arearefs="class16"> <para> - <literal>lazy</literal> (optional): Lazy fetching may be completely disabled by setting + <literal>lazy</literal> (optional): lazy fetching can be disabled by setting <literal>lazy="false"</literal>. </para> </callout> <callout arearefs="class17"> <para> - <literal>entity-name</literal> (optional, defaults to the class name): Hibernate3 - allows a class to be mapped multiple times (to different tables, potentially), - and allows entity mappings that are represented by Maps or XML at the Java level. + <literal>entity-name</literal> (optional - defaults to the class name): Hibernate3 + allows a class to be mapped multiple times, potentially to different tables. + It also allows entity mappings that are represented by Maps or XML at the Java level. In these cases, you should provide an explicit arbitrary name for the entity. See <xref linkend="persistent-classes-dynamicmodels"/> and <xref linkend="xml"/> for more information. @@ -457,28 +457,27 @@ </callout> <callout arearefs="class18"> <para> - <literal>check</literal> (optional): A SQL expression used to generate a multi-row + <literal>check</literal> (optional): an SQL expression used to generate a multi-row <emphasis>check</emphasis> constraint for automatic schema generation. </para> </callout> <callout arearefs="class19"> <para> - <literal>rowid</literal> (optional): Hibernate can use so called ROWIDs on databases - which support. E.g. on Oracle, Hibernate can use the <literal>rowid</literal> extra - column for fast updates if you set this option to <literal>rowid</literal>. A ROWID + <literal>rowid</literal> (optional): Hibernate can use ROWIDs on databases. On Oracle, for example, Hibernate can use the <literal>rowid</literal> extra + column for fast updates once this option has been set to <literal>rowid</literal>. A ROWID is an implementation detail and represents the physical location of a stored tuple. </para> </callout> <callout arearefs="class20"> <para> - <literal>subselect</literal> (optional): Maps an immutable and read-only entity - to a database subselect. Useful if you want to have a view instead of a base table, - but don't. See below for more information. + <literal>subselect</literal> (optional): maps an immutable and read-only entity + to a database subselect. This is useful if you want to have a view instead of a base table. + See below for more information. </para> </callout> <callout arearefs="class21"> <para> - <literal>abstract</literal> (optional): Used to mark abstract superclasses in + <literal>abstract</literal> (optional): is used to mark abstract superclasses in <literal>&lt;union-subclass&gt;</literal> hierarchies. </para> </callout> @@ -486,57 +485,57 @@ </programlistingco> <para> - It is perfectly acceptable for the named persistent class to be an interface. You would then + It is acceptable for the named persistent class to be an interface. You can declare implementing classes of that interface using the <literal>&lt;subclass&gt;</literal> - element. You may persist any <emphasis>static</emphasis> inner class. You should specify the - class name using the standard form ie. <literal>eg.Foo$Bar</literal>. + element. You can persist any <emphasis>static</emphasis> inner class. Specify the + class name using the standard form i.e. <literal>e.g.Foo$Bar</literal>. </para> <para> - Immutable classes, <literal>mutable="false"</literal>, may not be updated or deleted by the + Immutable classes, <literal>mutable="false"</literal>, cannot be updated or deleted by the application. This allows Hibernate to make some minor performance optimizations. </para> <para> The optional <literal>proxy</literal> attribute enables lazy initialization of persistent - instances of the class. Hibernate will initially return CGLIB proxies which implement - the named interface. The actual persistent object will be loaded when a method of the + instances of the class. Hibernate will initially return CGLIB proxies that implement + the named interface. The persistent object will load when a method of the proxy is invoked. See "Initializing collections and proxies" below. </para> <para><emphasis>Implicit</emphasis> polymorphism means that instances of the class will be returned - by a query that names any superclass or implemented interface or the class and that instances + by a query that names any superclass or implemented interface or class, and that instances of any subclass of the class will be returned by a query that names the class itself. <emphasis>Explicit</emphasis> polymorphism means that class instances will be returned only - by queries that explicitly name that class and that queries that name the class will return + by queries that explicitly name that class. Queries that name the class will return only instances of subclasses mapped inside this <literal>&lt;class&gt;</literal> declaration as a <literal>&lt;subclass&gt;</literal> or <literal>&lt;joined-subclass&gt;</literal>. For - most purposes the default, <literal>polymorphism="implicit"</literal>, is appropriate. + most purposes, the default <literal>polymorphism="implicit"</literal> is appropriate. Explicit polymorphism is useful when two different classes are mapped to the same table - (this allows a "lightweight" class that contains a subset of the table columns). + This allows a "lightweight" class that contains a subset of the table columns. </para> <para> The <literal>persister</literal> attribute lets you customize the persistence strategy used for - the class. You may, for example, specify your own subclass of - <literal>org.hibernate.persister.EntityPersister</literal> or you might even provide a + the class. You can, for example, specify your own subclass of + <literal>org.hibernate.persister.EntityPersister</literal>, or you can even provide a completely new implementation of the interface - <literal>org.hibernate.persister.ClassPersister</literal> that implements persistence via, - for example, stored procedure calls, serialization to flat files or LDAP. See - <literal>org.hibernate.test.CustomPersister</literal> for a simple example (of "persistence" - to a <literal>Hashtable</literal>). + <literal>org.hibernate.persister.ClassPersister</literal> that implements, for example, persistence via + stored procedure calls, serialization to flat files or LDAP. See + <literal>org.hibernate.test.CustomPersister</literal> for a simple example of "persistence" + to a <literal>Hashtable</literal>. </para> <para> - Note that the <literal>dynamic-update</literal> and <literal>dynamic-insert</literal> - settings are not inherited by subclasses and so may also be specified on the + The <literal>dynamic-update</literal> and <literal>dynamic-insert</literal> + settings are not inherited by subclasses, so they can also be specified on the <literal>&lt;subclass&gt;</literal> or <literal>&lt;joined-subclass&gt;</literal> elements. - These settings may increase performance in some cases, but might actually decrease - performance in others. Use judiciously. + Although these settings can increase performance in some cases, they can actually decrease + performance in others. </para> <para> - Use of <literal>select-before-update</literal> will usually decrease performance. It is very + Use of <literal>select-before-update</literal> will usually decrease performance. It is useful to prevent a database update trigger being called unnecessarily if you reattach a graph of detached instances to a <literal>Session</literal>. </para> @@ -548,37 +547,37 @@ <itemizedlist> <listitem> <para> - <literal>version</literal> check the version/timestamp columns + <literal>version</literal>: check the version/timestamp columns </para> </listitem> <listitem> <para> - <literal>all</literal> check all columns + <literal>all</literal>: check all columns </para> </listitem> <listitem> <para> - <literal>dirty</literal> check the changed columns, allowing some concurrent updates + <literal>dirty</literal>: check the changed columns, allowing some concurrent updates </para> </listitem> <listitem> <para> - <literal>none</literal> do not use optimistic locking + <literal>none</literal>: do not use optimistic locking </para> </listitem> </itemizedlist> <para> - We <emphasis>very</emphasis> strongly recommend that you use version/timestamp - columns for optimistic locking with Hibernate. This is the optimal strategy with - respect to performance and is the only strategy that correctly handles modifications - made to detached instances (ie. when <literal>Session.merge()</literal> is used). + It is <emphasis>strongly</emphasis> recommended that you use version/timestamp + columns for optimistic locking with Hibernate. + This strategy optimizes performance and correctly handles modifications + made to detached instances (i.e. when <literal>Session.merge()</literal> is used). </para> <para> - There is no difference between a view and a base table for a Hibernate mapping, as - expected this is transparent at the database level (note that some DBMS don't support - views properly, especially with updates). Sometimes you want to use a view, but can't - create one in the database (ie. with a legacy schema). In this case, you can map an + There is no difference between a view and a base table for a Hibernate mapping. + This is transparent at the database level, although some DBMS do not support + views properly, especially with updates. Sometimes you want to use a view, but you cannot + create one in the database (i.e. with a legacy schema). In this case, you can map an immutable and read-only entity to a given SQL subselect expression: </para> @@ -597,8 +596,8 @@ <para> Declare the tables to synchronize this entity with, ensuring that auto-flush happens - correctly, and that queries against the derived entity do not return stale data. - The <literal>&lt;subselect&gt;</literal> is available as both as an attribute and + correctly and that queries against the derived entity do not return stale data. + The <literal>&lt;subselect&gt;</literal> is available both as an attribute and a nested mapping element. </para> @@ -635,31 +634,31 @@ <calloutlist> <callout arearefs="id1"> <para> - <literal>name</literal> (optional): The name of the identifier property. + <literal>name</literal> (optional): the name of the identifier property. </para> </callout> <callout arearefs="id2"> <para> - <literal>type</literal> (optional): A name that indicates the Hibernate type. + <literal>type</literal> (optional): a name that indicates the Hibernate type. </para> </callout> <callout arearefs="id3"> <para> - <literal>column</literal> (optional - defaults to the property name): The + <literal>column</literal> (optional - defaults to the property name): the name of the primary key column. </para> </callout> <callout arearefs="id4"> <para> <literal>unsaved-value</literal> (optional - defaults to a "sensible" value): - An identifier property value that indicates that an instance is newly instantiated + an identifier property value that indicates an instance is newly instantiated (unsaved), distinguishing it from detached instances that were saved or loaded in a previous session. </para> </callout> <callout arearefs="id5"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The + <literal>access</literal> (optional - defaults to <literal>property</literal>): the strategy Hibernate should use for accessing the property value. </para> </callout> @@ -676,8 +675,8 @@ </para> <para> - There is an alternative <literal>&lt;composite-id&gt;</literal> declaration to allow access to - legacy data with composite keys. We strongly discourage its use for anything else. + There is an alternative <literal>&lt;composite-id&gt;</literal> declaration that allows access to + legacy data with composite keys. Its use is strongly discouraged for anything else. </para> <sect3 id="mapping-declaration-id-generator" revision="2"> @@ -699,9 +698,9 @@ <para> All generators implement the interface <literal>org.hibernate.id.IdentifierGenerator</literal>. - This is a very simple interface; some applications may choose to provide their own specialized - implementations. However, Hibernate provides a range of built-in implementations. There are shortcut - names for the built-in generators: + This is a very simple interface. Some applications can choose to provide their own specialized + implementations, however, Hibernate provides a range of built-in implementations. The shortcut + names for the built-in generators are as follows: <variablelist> <varlistentry> @@ -761,9 +760,9 @@ <term><literal>uuid</literal></term> <listitem> <para> - uses a 128-bit UUID algorithm to generate identifiers of type string, + uses a 128-bit UUID algorithm to generate identifiers of type string that are unique within a network (the IP address is used). The UUID is encoded - as a string of hexadecimal digits of length 32. + as a string of 32 hexadecimal digits in length. </para> </listitem> </varlistentry> @@ -779,7 +778,7 @@ <term><literal>native</literal></term> <listitem> <para> - picks <literal>identity</literal>, <literal>sequence</literal> or + selects <literal>identity</literal>, <literal>sequence</literal> or <literal>hilo</literal> depending upon the capabilities of the underlying database. </para> @@ -789,7 +788,7 @@ <term><literal>assigned</literal></term> <listitem> <para> - lets the application to assign an identifier to the object before + lets the application assign an identifier to the object before <literal>save()</literal> is called. This is the default strategy if no <literal>&lt;generator&gt;</literal> element is specified. </para> @@ -799,7 +798,7 @@ <term><literal>select</literal></term> <listitem> <para> - retrieves a primary key assigned by a database trigger by selecting + retrieves a primary key, assigned by a database trigger, by selecting the row by some unique key and retrieving the primary key value. </para> </listitem> @@ -808,7 +807,7 @@ <term><literal>foreign</literal></term> <listitem> <para> - uses the identifier of another associated object. Usually used in conjunction + uses the identifier of another associated object. It is usually used in conjunction with a <literal>&lt;one-to-one&gt;</literal> primary key association. </para> </listitem> @@ -817,12 +816,12 @@ <term><literal>sequence-identity</literal></term> <listitem> <para> - a specialized sequence generation strategy which utilizes a + a specialized sequence generation strategy that utilizes a database sequence for the actual value generation, but combines - this with JDBC3 getGeneratedKeys to actually return the generated - identifier value as part of the insert statement execution. This - strategy is only known to be supported on Oracle 10g drivers - targetted for JDK 1.4. Note comments on these insert statements + this with JDBC3 getGeneratedKeys to return the generated + identifier value as part of the insert statement execution. This + strategy is only supported on Oracle 10g drivers + targeted for JDK 1.4. Comments on these insert statements are disabled due to a bug in the Oracle drivers. </para> </listitem> @@ -836,9 +835,9 @@ <title>Hi/lo algorithm</title> <para> The <literal>hilo</literal> and <literal>seqhilo</literal> generators provide two alternate - implementations of the hi/lo algorithm, a favorite approach to identifier generation. The + implementations of the hi/lo algorithm. The first implementation requires a "special" database table to hold the next available "hi" value. - The second uses an Oracle-style sequence (where supported). + Where supported, the second uses an Oracle-style sequence. </para> <programlisting><![CDATA[<id name="id" type="long" column="cat_id"> @@ -857,9 +856,9 @@ </id>]]></programlisting> <para> - Unfortunately, you can't use <literal>hilo</literal> when supplying your own - <literal>Connection</literal> to Hibernate. When Hibernate is using an application - server datasource to obtain connections enlisted with JTA, you must properly configure + Unfortunately, you cannot use <literal>hilo</literal> when supplying your own + <literal>Connection</literal> to Hibernate. When Hibernate uses an application + server datasource to obtain connections enlisted with JTA, you must configure the <literal>hibernate.transaction.manager_lookup_class</literal>. </para> </sect3> @@ -867,21 +866,21 @@ <sect3 id="mapping-declaration-id-uuid"> <title>UUID algorithm</title> <para> - The UUID contains: IP address, startup time of the JVM (accurate to a quarter - second), system time and a counter value (unique within the JVM). It's not + The UUID contains: IP address, startup time of the JVM that is accurate to a quarter + second, system time and a counter value that is unique within the JVM. It is not possible to obtain a MAC address or memory address from Java code, so this is - the best we can do without using JNI. + the best option without using JNI. </para> </sect3> <sect3 id="mapping-declaration-id-sequences"> <title>Identity columns and sequences</title> <para> - For databases which support identity columns (DB2, MySQL, Sybase, MS SQL), you - may use <literal>identity</literal> key generation. For databases that support - sequences (DB2, Oracle, PostgreSQL, Interbase, McKoi, SAP DB) you may use - <literal>sequence</literal> style key generation. Both these strategies require - two SQL queries to insert a new object. + For databases that support identity columns (DB2, MySQL, Sybase, MS SQL), you + can use <literal>identity</literal> key generation. For databases that support + sequences (DB2, Oracle, PostgreSQL, Interbase, McKoi, SAP DB) you can use + <literal>sequence</literal> style key generation. Both of these strategies require + two SQL queries to insert a new object. For example: </para> <programlisting><![CDATA[<id name="id" type="long" column="person_id"> @@ -895,27 +894,26 @@ </id>]]></programlisting> <para> - For cross-platform development, the <literal>native</literal> strategy will + For cross-platform development, the <literal>native</literal> strategy will, depending on the capabilities of the underlying database, choose from the <literal>identity</literal>, <literal>sequence</literal> and - <literal>hilo</literal> strategies, dependant upon the capabilities of the - underlying database. + <literal>hilo</literal> strategies. </para> </sect3> <sect3 id="mapping-declaration-id-assigned"> <title>Assigned identifiers</title> <para> - If you want the application to assign identifiers (as opposed to having - Hibernate generate them), you may use the <literal>assigned</literal> generator. - This special generator will use the identifier value already assigned to the - object's identifier property. This generator is used when the primary key + If you want the application to assign identifiers, as opposed to having + Hibernate generate them, you can use the <literal>assigned</literal> generator. + This special generator uses the identifier value already assigned to the + object's identifier property. The generator is used when the primary key is a natural key instead of a surrogate key. This is the default behavior - if you do no specify a <literal>&lt;generator&gt;</literal> element. + if you do not specify a <literal>&lt;generator&gt;</literal> element. </para> <para> - Choosing the <literal>assigned</literal> generator makes Hibernate use - <literal>unsaved-value="undefined"</literal>, forcing Hibernate to go to + The <literal>assigned</literal> generator makes Hibernate use + <literal>unsaved-value="undefined"</literal>. This forces Hibernate to go to the database to determine if an instance is transient or detached, unless there is a version or timestamp property, or you define <literal>Interceptor.isUnsaved()</literal>. @@ -925,7 +923,7 @@ <sect3 id="mapping-declaration-id-select"> <title>Primary keys assigned by triggers</title> <para> - For legacy schemas only (Hibernate does not generate DDL with triggers). + Hibernate does not generate DDL with triggers. It is for legacy schemas only. </para> <programlisting><![CDATA[<id name="id" type="long" column="person_id"> @@ -936,8 +934,8 @@ <para> In the above example, there is a unique valued property named - <literal>socialSecurityNumber</literal> defined by the class, as a - natural key, and a surrogate key named <literal>person_id</literal> + <literal>socialSecurityNumber</literal>. It is defined by the class, as a + natural key and a surrogate key named <literal>person_id</literal>, whose value is generated by a trigger. </para> @@ -946,127 +944,127 @@ </sect2> <sect2 id="mapping-declaration-id-enhanced"> - <title>Enhanced identifier generators</title> + <title>Enhanced identifier generators</title>composite <para> Starting with release 3.2.3, there are 2 new generators which represent a re-thinking of 2 different aspects of identifier generation. The first aspect is database portability; the second is optimization - (not having to query the database for every request for a new identifier value). These two new - generators are intended to take the place of some of the named generators described above (starting - in 3.3.x); however, they are included in the current releases and can be referenced by FQN. + Optimization means that you do not have to query the database for every request for a new identifier value. These two new + generators are intended to take the place of some of the named generators described above, starting + in 3.3.x. However, they are included in the current releases and can be referenced by FQN. </para> <para> The first of these new generators is <literal>org.hibernate.id.enhanced.SequenceStyleGenerator</literal> - which is intended firstly as a replacement for the <literal>sequence</literal> generator and secondly as - a better portability generator than <literal>native</literal> (because <literal>native</literal> - (generally) chooses between <literal>identity</literal> and <literal>sequence</literal> which have - largely different semantics which can cause subtle isssues in applications eyeing portability). - <literal>org.hibernate.id.enhanced.SequenceStyleGenerator</literal> however achieves portability in - a different manner. It chooses between using a table or a sequence in the database to store its - incrementing values depending on the capabilities of the dialect being used. The difference between this + which is intended, firstly, as a replacement for the <literal>sequence</literal> generator and, secondly, as + a better portability generator than <literal>native</literal>. This is because <literal>native</literal> + generally chooses between <literal>identity</literal> and <literal>sequence</literal> which have + largely different semantics that can cause subtle issues in applications eyeing portability. + <literal>org.hibernate.id.enhanced.SequenceStyleGenerator</literal>, however, achieves portability in + a different manner. It chooses between a table or a sequence in the database to store its + incrementing values, depending on the capabilities of the dialect being used. The difference between this and <literal>native</literal> is that table-based and sequence-based storage have the same exact - semantic (in fact sequences are exactly what Hibernate tries to emmulate with its table-based - generators). This generator has a number of configuration parameters: + semantic. In fact, sequences are exactly what Hibernate tries to emulate with its table-based + generators. This generator has a number of configuration parameters: <itemizedlist spacing="compact"> <listitem> <para> <literal>sequence_name</literal> (optional, defaults to <literal>hibernate_sequence</literal>): - The name of the sequence (or table) to be used. + the name of the sequence or table to be used. </para> </listitem> <listitem> <para> - <literal>initial_value</literal> (optional, defaults to <literal>1</literal>): The initial + <literal>initial_value</literal> (optional, defaults to <literal>1</literal>): the initial value to be retrieved from the sequence/table. In sequence creation terms, this is analogous - to the clause typical named "STARTS WITH". + to the clause typically named "STARTS WITH". </para> </listitem> <listitem> <para> - <literal>increment_size</literal> (optional, defaults to <literal>1</literal>): The value by + <literal>increment_size</literal> (optional - defaults to <literal>1</literal>): the value by which subsequent calls to the sequence/table should differ. In sequence creation terms, this - is analogous to the clause typical named "INCREMENT BY". + is analogous to the clause typically named "INCREMENT BY". </para> </listitem> <listitem> <para> - <literal>force_table_use</literal> (optional, defaults to <literal>false</literal>): Should + <literal>force_table_use</literal> (optional - defaults to <literal>false</literal>): should we force the use of a table as the backing structure even though the dialect might support sequence? </para> </listitem> <listitem> <para> - <literal>value_column</literal> (optional, defaults to <literal>next_val</literal>): Only - relevant for table structures! The name of the column on the table which is used to + <literal>value_column</literal> (optional - defaults to <literal>next_val</literal>): only + relevant for table structures, it is the name of the column on the table which is used to hold the value. </para> </listitem> <listitem> <para> - <literal>optimizer</literal> (optional, defaults to <literal>none</literal>): + <literal>optimizer</literal> (optional - defaults to <literal>none</literal>): See <xref linkend="mapping-declaration-id-enhanced-optimizers"/> </para> </listitem> </itemizedlist> </para> <para> - The second of these new generators is <literal>org.hibernate.id.enhanced.TableGenerator</literal> which - is intended firstly as a replacement for the <literal>table</literal> generator (although it actually - functions much more like <literal>org.hibernate.id.MultipleHiLoPerTableGenerator</literal>) and secondly - as a re-implementation of <literal>org.hibernate.id.MultipleHiLoPerTableGenerator</literal> utilizing the - notion of pluggable optimiziers. Essentially this generator defines a table capable of holding + The second of these new generators is <literal>org.hibernate.id.enhanced.TableGenerator</literal>, which + is intended, firstly, as a replacement for the <literal>table</literal> generator, even though it actually + functions much more like <literal>org.hibernate.id.MultipleHiLoPerTableGenerator</literal>, and secondly, + as a re-implementation of <literal>org.hibernate.id.MultipleHiLoPerTableGenerator</literal> that utilizes the + notion of pluggable optimizers. Essentially this generator defines a table capable of holding a number of different increment values simultaneously by using multiple distinctly keyed rows. This generator has a number of configuration parameters: <itemizedlist spacing="compact"> <listitem> <para> - <literal>table_name</literal> (optional, defaults to <literal>hibernate_sequences</literal>): - The name of the table to be used. + <literal>table_name</literal> (optional - defaults to <literal>hibernate_sequences</literal>): + the name of the table to be used. </para> </listitem> <listitem> <para> - <literal>value_column_name</literal> (optional, defaults to <literal>next_val</literal>): - The name of the column on the table which is used to hold the value. + <literal>value_column_name</literal> (optional - defaults to <literal>next_val</literal>): + the name of the column on the table that is used to hold the value. </para> </listitem> <listitem> <para> - <literal>segment_column_name</literal> (optional, defaults to <literal>sequence_name</literal>): - The name of the column on the table which is used to hold the "segement key". This is the - value which distinctly identifies which increment value to use. + <literal>segment_column_name</literal> (optional - defaults to <literal>sequence_name</literal>): + the name of the column on the table that is used to hold the "segment key". This is the + value which identifies which increment value to use. </para> </listitem> <listitem> <para> - <literal>segment_value</literal> (optional, defaults to <literal>default</literal>): + <literal>segment_value</literal> (optional - defaults to <literal>default</literal>): The "segment key" value for the segment from which we want to pull increment values for this generator. </para> </listitem> <listitem> <para> - <literal>segment_value_length</literal> (optional, defaults to <literal>255</literal>): + <literal>segment_value_length</literal> (optional - defaults to <literal>255</literal>): Used for schema generation; the column size to create this segment key column. </para> </listitem> <listitem> <para> - <literal>initial_value</literal> (optional, defaults to <literal>1</literal>): + <literal>initial_value</literal> (optional - defaults to <literal>1</literal>): The initial value to be retrieved from the table. </para> </listitem> <listitem> <para> - <literal>increment_size</literal> (optional, defaults to <literal>1</literal>): + <literal>increment_size</literal> (optional - defaults to <literal>1</literal>): The value by which subsequent calls to the table should differ. </para> </listitem> <listitem> <para> - <literal>optimizer</literal> (optional, defaults to <literal></literal>): + <literal>optimizer</literal> (optional - defaults to <literal></literal>): See <xref linkend="mapping-declaration-id-enhanced-optimizers"/> </para> </listitem> @@ -1077,34 +1075,34 @@ <sect2 id="mapping-declaration-id-enhanced-optimizers"> <title>Identifier generator optimization</title> <para> - For identifier generators which store values in the database, it is inefficient for them to hit the - database on each and every call to generate a new identifier value. Instead, you'd ideally want to + For identifier generators that store values in the database, it is inefficient for them to hit the + database on each and every call to generate a new identifier value. Instead, you can group a bunch of them in memory and only hit the database when you have exhausted your in-memory value group. This is the role of the pluggable optimizers. Currently only the two enhanced generators - (<xref linkend="mapping-declaration-id-enhanced"/> support this notion. + (<xref linkend="mapping-declaration-id-enhanced"/> support this operation. <itemizedlist spacing="compact"> <listitem> <para> - <literal>none</literal> (generally this is the default if no optimizer was specified): This - says to not perform any optimizations, and hit the database each and every request. + <literal>none</literal> (generally this is the default if no optimizer was specified): this + will not perform any optimizations and hit the database for each and every request. </para> </listitem> <listitem> <para> <literal>hilo</literal>: applies a hi/lo algorithm around the database retrieved values. The values from the database for this optimizer are expected to be sequential. The values - retrieved from the database structure for this optimizer indicates the "group number"; the + retrieved from the database structure for this optimizer indicates the "group number". The <literal>increment_size</literal> is multiplied by that value in memory to define a group "hi value". </para> </listitem> <listitem> <para> - <literal>pooled</literal>: like was discussed for <literal>hilo</literal>, this optimizers + <literal>pooled</literal>: as with the case of <literal>hilo</literal>, this optimizer attempts to minimize the number of hits to the database. Here, however, we simply store the starting value for the "next group" into the database structure rather than a sequential - value in combination with an in-memory grouping algorithm. <literal>increment_size</literal> - here refers to the values coming from the database. + value in combination with an in-memory grouping algorithm. Here, <literal>increment_size</literal> + refers to the values coming from the database. </para> </listitem> </itemizedlist> @@ -1127,7 +1125,7 @@ </composite-id>]]></programlisting> <para> - For a table with a composite key, you may map multiple properties of the class + A table with a composite key can be mapped with multiple properties of the class as identifier properties. The <literal>&lt;composite-id&gt;</literal> element accepts <literal>&lt;key-property&gt;</literal> property mappings and <literal>&lt;key-many-to-one&gt;</literal> mappings as child elements. @@ -1139,13 +1137,13 @@ </composite-id>]]></programlisting> <para> - Your persistent class <emphasis>must</emphasis> override <literal>equals()</literal> + The persistent class <emphasis>must</emphasis> override <literal>equals()</literal> and <literal>hashCode()</literal> to implement composite identifier equality. It must - also implements <literal>Serializable</literal>. + also implement <literal>Serializable</literal>. </para> <para> - Unfortunately, this approach to composite identifiers means that a persistent object + Unfortunately, this approach means that a persistent object is its own identifier. There is no convenient "handle" other than the object itself. You must instantiate an instance of the persistent class itself and populate its identifier properties before you can <literal>load()</literal> the persistent state @@ -1168,9 +1166,9 @@ In this example, both the composite identifier class, <literal>MedicareId</literal>, and the entity class itself have properties named <literal>medicareNumber</literal> and <literal>dependent</literal>. The identifier class must override - <literal>equals()</literal> and <literal>hashCode()</literal> and implement. - <literal>Serializable</literal>. The disadvantage of this approach is quite - obvious&mdash;code duplication. + <literal>equals()</literal> and <literal>hashCode()</literal> and implement + <literal>Serializable</literal>. The main disadvantage of this approach is + code duplication. </para> <para> @@ -1180,7 +1178,7 @@ <itemizedlist spacing="compact"> <listitem> <para> - <literal>mapped</literal> (optional, defaults to <literal>false</literal>): + <literal>mapped</literal> (optional - defaults to <literal>false</literal>): indicates that a mapped composite identifier is used, and that the contained property mappings refer to both the entity class and the composite identifier class. @@ -1188,14 +1186,14 @@ </listitem> <listitem> <para> - <literal>class</literal> (optional, but required for a mapped composite identifier): - The class used as a composite identifier. + <literal>class</literal> (optional - but required for a mapped composite identifier): + the class used as a composite identifier. </para> </listitem> </itemizedlist> <para> - We will describe a third, even more convenient approach where the composite identifier + We will describe a third, even more convenient approach, where the composite identifier is implemented as a component class in <xref linkend="components-compositeid"/>. The attributes described below apply only to this alternative approach: </para> @@ -1203,39 +1201,39 @@ <itemizedlist spacing="compact"> <listitem> <para> - <literal>name</literal> (optional, required for this approach): A property of - component type that holds the composite identifier (see chapter 9). + <literal>name</literal> (optional - required for this approach): a property of + component type that holds the composite identifier. Please see chapter 9 for more information. </para> </listitem> <listitem> <para> <literal>access</literal> (optional - defaults to <literal>property</literal>): - The strategy Hibernate should use for accessing the property value. + the strategy Hibernate uses for accessing the property value. </para> </listitem> <listitem> <para> <literal>class</literal> (optional - defaults to the property type determined by - reflection): The component class used as a composite identifier (see next section). + reflection): the component class used as a composite identifier. Please see the next section for more information. </para> </listitem> </itemizedlist> <para> - This third approach, an <emphasis>identifier component</emphasis> is the one we recommend + The third approach, an <emphasis>identifier component</emphasis>, is recommended for almost all applications. </para> </sect2> <sect2 id="mapping-declaration-discriminator" revision="3"> - <title>discriminator</title> + <title>Discriminator</title> <para> The <literal>&lt;discriminator&gt;</literal> element is required for polymorphic persistence - using the table-per-class-hierarchy mapping strategy and declares a discriminator column of the + using the table-per-class-hierarchy mapping strategy. It declares a discriminator column of the table. The discriminator column contains marker values that tell the persistence layer what - subclass to instantiate for a particular row. A restricted set of types may be used: + subclass to instantiate for a particular row. A restricted set of types can be used: <literal>string</literal>, <literal>character</literal>, <literal>integer</literal>, <literal>byte</literal>, <literal>short</literal>, <literal>boolean</literal>, <literal>yes_no</literal>, <literal>true_false</literal>. @@ -1259,35 +1257,35 @@ <calloutlist> <callout arearefs="discriminator1"> <para> - <literal>column</literal> (optional - defaults to <literal>class</literal>) the + <literal>column</literal> (optional - defaults to <literal>class</literal>): the name of the discriminator column. </para> </callout> <callout arearefs="discriminator2"> <para> - <literal>type</literal> (optional - defaults to <literal>string</literal>) a + <literal>type</literal> (optional - defaults to <literal>string</literal>): a name that indicates the Hibernate type </para> </callout> <callout arearefs="discriminator3"> <para> - <literal>force</literal> (optional - defaults to <literal>false</literal>) - "force" Hibernate to specify allowed discriminator values even when retrieving + <literal>force</literal> (optional - defaults to <literal>false</literal>): + "forces" Hibernate to specify the allowed discriminator values, even when retrieving all instances of the root class. </para> </callout> <callout arearefs="discriminator4"> <para> - <literal>insert</literal> (optional - defaults to <literal>true</literal>) + <literal>insert</literal> (optional - defaults to <literal>true</literal>): set this to <literal>false</literal> if your discriminator column is also part - of a mapped composite identifier. (Tells Hibernate to not include the column - in SQL <literal>INSERT</literal>s.) + of a mapped composite identifier. It tells Hibernate not to include the column + in SQL <literal>INSERTs</literal>. </para> </callout> <callout arearefs="discriminator5"> <para> - <literal>formula</literal> (optional) an arbitrary SQL expression that is - executed when a type has to be evaluated. Allows content-based discrimination. + <literal>formula</literal> (optional): an arbitrary SQL expression that is + executed when a type has to be evaluated. It allows content-based discrimination. </para> </callout> </calloutlist> @@ -1300,14 +1298,14 @@ </para> <para> - The <literal>force</literal> attribute is (only) useful if the table contains rows with + The <literal>force</literal> attribute is only useful if the table contains rows with "extra" discriminator values that are not mapped to a persistent class. This will not usually be the case. </para> <para> - Using the <literal>formula</literal> attribute you can declare an arbitrary SQL expression - that will be used to evaluate the type of a row: + The <literal>formula</literal> attribute allows you to declare an arbitrary SQL expression + that will be used to evaluate the type of a row. For example: </para> <programlisting><![CDATA[<discriminator @@ -1317,12 +1315,12 @@ </sect2> <sect2 id="mapping-declaration-version" revision="4"> - <title>version (optional)</title> + <title>Version (optional)</title> <para> The <literal>&lt;version&gt;</literal> element is optional and indicates that the table contains versioned data. This is particularly useful if you plan to - use <emphasis>long transactions</emphasis> (see below). + use <emphasis>long transactions</emphasis>. See below for more information: </para> <programlistingco> @@ -1348,48 +1346,48 @@ <calloutlist> <callout arearefs="version1"> <para> - <literal>column</literal> (optional - defaults to the property name): The name + <literal>column</literal> (optional - defaults to the property name): the name of the column holding the version number. </para> </callout> <callout arearefs="version2"> <para> - <literal>name</literal>: The name of a property of the persistent class. + <literal>name</literal>: the name of a property of the persistent class. </para> </callout> <callout arearefs="version3"> <para> <literal>type</literal> (optional - defaults to <literal>integer</literal>): - The type of the version number. + the type of the version number. </para> </callout> <callout arearefs="version4"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the property value. + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses to access the property value. </para> </callout> <callout arearefs="version5"> <para> <literal>unsaved-value</literal> (optional - defaults to <literal>undefined</literal>): - A version property value that indicates that an instance is newly instantiated + a version property value that indicates that an instance is newly instantiated (unsaved), distinguishing it from detached instances that were saved or loaded - in a previous session. (<literal>undefined</literal> specifies that the identifier - property value should be used.) + in a previous session. <literal>Undefined</literal> specifies that the identifier + property value should be used. </para> </callout> <callout arearefs="version6"> <para> <literal>generated</literal> (optional - defaults to <literal>never</literal>): - Specifies that this version property value is actually generated by the database. - See the discussion of <link linkend="mapping-generated">generated properties</link>. + specifies that this version property value is generated by the database. + See the discussion of <link linkend="mapping-generated">generated properties</link> for more information. </para> </callout> <callout arearefs="version7"> <para> <literal>insert</literal> (optional - defaults to <literal>true</literal>): - Specifies whether the version column should be included in SQL insert statements. - May be set to <literal>false</literal> if and only if the database column + specifies whether the version column should be included in SQL insert statements. + It can be set to <literal>false</literal> if the database column is defined with a default value of <literal>0</literal>. </para> </callout> @@ -1397,26 +1395,26 @@ </programlistingco> <para> - Version numbers may be of Hibernate type <literal>long</literal>, <literal>integer</literal>, + Version numbers can be of Hibernate type <literal>long</literal>, <literal>integer</literal>, <literal>short</literal>, <literal>timestamp</literal> or <literal>calendar</literal>. </para> <para> - A version or timestamp property should never be null for a detached instance, so - Hibernate will detect any instance with a null version or timestamp as transient, - no matter what other <literal>unsaved-value</literal> strategies are specified. + A version or timestamp property should never be null for a detached instance. + Hibernate will detect any instance with a null version or timestamp as transient, + irrespective of what other <literal>unsaved-value</literal> strategies are specified. <emphasis>Declaring a nullable version or timestamp property is an easy way to avoid - any problems with transitive reattachment in Hibernate, especially useful for people - using assigned identifiers or composite keys!</emphasis> + problems with transitive reattachment in Hibernate. It is especially useful for people + using assigned identifiers or composite keys</emphasis>. </para> </sect2> <sect2 id="mapping-declaration-timestamp" revision="4" > - <title>timestamp (optional)</title> + <title>Timestamp (optional)</title> <para> The optional <literal>&lt;timestamp&gt;</literal> element indicates that the table contains - timestamped data. This is intended as an alternative to versioning. Timestamps are by nature + timestamped data. This provides an alternative to versioning. Timestamps are a less safe implementation of optimistic locking. However, sometimes the application might use the timestamps in other ways. </para> @@ -1442,68 +1440,73 @@ <calloutlist> <callout arearefs="timestamp1"> <para> - <literal>column</literal> (optional - defaults to the property name): The name + <literal>column</literal> (optional - defaults to the property name): the name of a column holding the timestamp. </para> </callout> <callout arearefs="timestamp2"> <para> - <literal>name</literal>: The name of a JavaBeans style property of + <literal>name</literal>: the name of a JavaBeans style property of Java type <literal>Date</literal> or <literal>Timestamp</literal> of the persistent class. </para> </callout> <callout arearefs="timestamp3"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the property value. + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses for accessing the property value. </para> </callout> <callout arearefs="timestamp4"> <para> <literal>unsaved-value</literal> (optional - defaults to <literal>null</literal>): - A version property value that indicates that an instance is newly instantiated + a version property value that indicates that an instance is newly instantiated (unsaved), distinguishing it from detached instances that were saved or loaded - in a previous session. (<literal>undefined</literal> specifies that the identifier - property value should be used.) + in a previous session. <literal>Undefined</literal> specifies that the identifier + property value should be used. </para> </callout> <callout arearefs="timestamp5"> <para> <literal>source</literal> (optional - defaults to <literal>vm</literal>): - From where should Hibernate retrieve the timestamp value? From the database, + Where should Hibernate retrieve the timestamp value from? From the database, or from the current JVM? Database-based timestamps incur an overhead because - Hibernate must hit the database in order to determine the "next value", - but will be safer for use in clustered environments. Note also, that not - all <literal>Dialect</literal>s are known to support retrieving of the - database's current timestamp, while others might be unsafe for usage - in locking due to lack of precision (Oracle 8 for example). + Hibernate must hit the database in order to determine the "next value". + It is safer to use in clustered environments. Not + all <literal>Dialects</literal> are known to support the retrieval of the + database's current timestamp. Others may also be unsafe for usage + in locking due to lack of precision (Oracle 8, for example). </para> </callout> <callout arearefs="timestamp6"> <para> <literal>generated</literal> (optional - defaults to <literal>never</literal>): - Specifies that this timestamp property value is actually generated by the database. - See the discussion of <link linkend="mapping-generated">generated properties</link>. + specifies that this timestamp property value is actually generated by the database. + See the discussion of <link linkend="mapping-generated">generated properties</link> for more information. </para> </callout> </calloutlist> </programlistingco> - <para> - Note that <literal>&lt;timestamp&gt;</literal> is equivalent to + + <note> + <title>Note</title> + <para> + <literal>&lt;Timestamp&gt;</literal> is equivalent to <literal>&lt;version type="timestamp"&gt;</literal>. And <literal>&lt;timestamp source="db"&gt;</literal> is equivalent to <literal>&lt;version type="dbtimestamp"&gt;</literal> - </para> + </para> + </note> + </sect2> <sect2 id="mapping-declaration-property" revision="4"> - <title>property</title> + <title>Property</title> <para> - The <literal>&lt;property&gt;</literal> element declares a persistent, JavaBean style + The <literal>&lt;property&gt;</literal> element declares a persistent JavaBean style property of the class. </para> @@ -1554,7 +1557,7 @@ <callout arearefs="property2"> <para> <literal>column</literal> (optional - defaults to the property name): the name - of the mapped database table column. This may also be specified by nested + of the mapped database table column. This can also be specified by nested <literal>&lt;column&gt;</literal> element(s). </para> </callout> @@ -1565,11 +1568,11 @@ </callout> <callout arearefs="property4-5"> <para> - <literal>update, insert</literal> (optional - defaults to <literal>true</literal>) : + <literal>update, insert</literal> (optional - defaults to <literal>true</literal>): specifies that the mapped columns should be included in SQL <literal>UPDATE</literal> and/or <literal>INSERT</literal> statements. Setting both to <literal>false</literal> allows a pure "derived" property whose value is initialized from some other - property that maps to the same colum(s) or by a trigger or other application. + property that maps to the same column(s), or by a trigger or other application. </para> </callout> <callout arearefs="property6"> @@ -1581,43 +1584,43 @@ </callout> <callout arearefs="property7"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the property value. + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses for accessing the property value. </para> </callout> <callout arearefs="property8"> <para> - <literal>lazy</literal> (optional - defaults to <literal>false</literal>): Specifies + <literal>lazy</literal> (optional - defaults to <literal>false</literal>): specifies that this property should be fetched lazily when the instance variable is first - accessed (requires build-time bytecode instrumentation). + accessed. It requires build-time bytecode instrumentation. </para> </callout> <callout arearefs="property9"> <para> - <literal>unique</literal> (optional): Enable the DDL generation of a unique + <literal>unique</literal> (optional): enables the DDL generation of a unique constraint for the columns. Also, allow this to be the target of a <literal>property-ref</literal>. </para> </callout> <callout arearefs="property10"> <para> - <literal>not-null</literal> (optional): Enable the DDL generation of a nullability + <literal>not-null</literal> (optional): enables the DDL generation of a nullability constraint for the columns. </para> </callout> <callout arearefs="property11"> <para> <literal>optimistic-lock</literal> (optional - defaults to <literal>true</literal>): - Specifies that updates to this property do or do not require acquisition of the - optimistic lock. In other words, determines if a version increment should occur when + specifies that updates to this property do or do not require acquisition of the + optimistic lock. In other words, it determines if a version increment should occur when this property is dirty. </para> </callout> <callout arearefs="property12"> <para> <literal>generated</literal> (optional - defaults to <literal>never</literal>): - Specifies that this property value is actually generated by the database. - See the discussion of <link linkend="mapping-generated">generated properties</link>. + specifies that this property value is actually generated by the database. + See the discussion of <link linkend="mapping-generated">generated properties</link> for more information. </para> </callout> </calloutlist> @@ -1630,14 +1633,14 @@ <orderedlist spacing="compact"> <listitem> <para> - The name of a Hibernate basic type (eg. <literal>integer, string, character, - date, timestamp, float, binary, serializable, object, blob</literal>). + The name of a Hibernate basic type: <literal>integer, string, character, + date, timestamp, float, binary, serializable, object, blob</literal> etc. </para> </listitem> <listitem> <para> - The name of a Java class with a default basic type (eg. <literal>int, float, - char, java.lang.String, java.util.Date, java.lang.Integer, java.sql.Clob</literal>). + The name of a Java class with a default basic type: <literal>int, float, + char, java.lang.String, java.util.Date, java.lang.Integer, java.sql.Clob</literal> etc. </para> </listitem> <listitem> @@ -1647,34 +1650,34 @@ </listitem> <listitem> <para> - The class name of a custom type (eg. <literal>com.illflow.type.MyCustomType</literal>). + The class name of a custom type: <literal>com.illflow.type.MyCustomType</literal> etc. </para> </listitem> </orderedlist> <para> If you do not specify a type, Hibernate will use reflection upon the named - property to take a guess at the correct Hibernate type. Hibernate will try to - interpret the name of the return class of the property getter using rules 2, 3, - 4 in that order. However, this is not always enough. - In certain cases you will still need the <literal>type</literal> - attribute. (For example, to distinguish between <literal>Hibernate.DATE</literal> and - <literal>Hibernate.TIMESTAMP</literal>, or to specify a custom type.) + property and guess the correct Hibernate type. Hibernate will attempt to + interpret the name of the return class of the property getter using, in order, rules 2, 3, + and 4. + In certain cases you will need the <literal>type</literal> + attribute. For example, to distinguish between <literal>Hibernate.DATE</literal> and + <literal>Hibernate.TIMESTAMP</literal>, or to specify a custom type. </para> <para> - The <literal>access</literal> attribute lets you control how Hibernate will access + The <literal>access</literal> attribute allows you to control how Hibernate accesses the property at runtime. By default, Hibernate will call the property get/set pair. If you specify <literal>access="field"</literal>, Hibernate will bypass the get/set - pair and access the field directly, using reflection. You may specify your own + pair and access the field directly using reflection. You can specify your own strategy for property access by naming a class that implements the interface <literal>org.hibernate.property.PropertyAccessor</literal>. </para> <para> - An especially powerful feature are derived properties. These properties are by - definition read-only, the property value is computed at load time. You declare - the computation as a SQL expression, this translates to a <literal>SELECT</literal> + A powerful feature is derived properties. These properties are by + definition read-only. The property value is computed at load time. You declare + the computation as an SQL expression. This then translates to a <literal>SELECT</literal> clause subquery in the SQL query that loads an instance: </para> @@ -1686,21 +1689,21 @@ AND li.orderNumber = orderNumber )"/>]]></programlisting> <para> - Note that you can reference the entities own table by not declaring an alias on - a particular column (<literal>customerId</literal> in the given example). Also note - that you can use the nested <literal>&lt;formula&gt;</literal> mapping element - if you don't like to use the attribute. + You can reference the entity table by not declaring an alias on + a particular column. This would be <literal>customerId</literal> in the given example. You can also use + the nested <literal>&lt;formula&gt;</literal> mapping element + if you do not want to use the attribute. </para> </sect2> <sect2 id="mapping-declaration-manytoone" revision="5"> - <title>many-to-one</title> + <title>Many-to-one</title> <para> An ordinary association to another persistent class is declared using a <literal>many-to-one</literal> element. The relational model is a - many-to-one association: a foreign key in one table is referencing + many-to-one association; a foreign key in one table is referencing the primary key column(s) of the target table. </para> @@ -1751,84 +1754,84 @@ <calloutlist> <callout arearefs="manytoone1"> <para> - <literal>name</literal>: The name of the property. + <literal>name</literal>: the name of the property. </para> </callout> <callout arearefs="manytoone2"> <para> - <literal>column</literal> (optional): The name of the foreign key column. - This may also be specified by nested <literal>&lt;column&gt;</literal> + <literal>column</literal> (optional): the name of the foreign key column. + This can also be specified by nested <literal>&lt;column&gt;</literal> element(s). </para> </callout> <callout arearefs="manytoone3"> <para> <literal>class</literal> (optional - defaults to the property type - determined by reflection): The name of the associated class. + determined by reflection): the name of the associated class. </para> </callout> <callout arearefs="manytoone4"> <para> - <literal>cascade</literal> (optional): Specifies which operations should + <literal>cascade</literal> (optional): specifies which operations should be cascaded from the parent object to the associated object. </para> </callout> <callout arearefs="manytoone5"> <para> <literal>fetch</literal> (optional - defaults to <literal>select</literal>): - Chooses between outer-join fetching or sequential select fetching. + chooses between outer-join fetching or sequential select fetching. </para> </callout> <callout arearefs="manytoone6-7"> <para> - <literal>update, insert</literal> (optional - defaults to <literal>true</literal>) + <literal>update, insert</literal> (optional - defaults to <literal>true</literal>): specifies that the mapped columns should be included in SQL <literal>UPDATE</literal> and/or <literal>INSERT</literal> statements. Setting both to <literal>false</literal> - allows a pure "derived" association whose value is initialized from some other - property that maps to the same colum(s) or by a trigger or other application. + allows a pure "derived" association whose value is initialized from another + property that maps to the same column(s), or by a trigger or other application. </para> </callout> <callout arearefs="manytoone8"> <para> - <literal>property-ref</literal>: (optional) The name of a property of the associated + <literal>property-ref</literal> (optional): the name of a property of the associated class that is joined to this foreign key. If not specified, the primary key of the associated class is used. </para> </callout> <callout arearefs="manytoone9"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the property value. + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses for accessing the property value. </para> </callout> <callout arearefs="manytoone10"> <para> - <literal>unique</literal> (optional): Enable the DDL generation of a unique - constraint for the foreign-key column. Also, allow this to be the target of - a <literal>property-ref</literal>. This makes the association multiplicity - effectively one to one. + <literal>unique</literal> (optional): enables the DDL generation of a unique + constraint for the foreign-key column. By allowing this to be the target of + a <literal>property-ref</literal>, you can make the association multiplicity + one-to-one. </para> </callout> <callout arearefs="manytoone11"> <para> - <literal>not-null</literal> (optional): Enable the DDL generation of a nullability + <literal>not-null</literal> (optional): enables the DDL generation of a nullability constraint for the foreign key columns. </para> </callout> <callout arearefs="manytoone12"> <para> <literal>optimistic-lock</literal> (optional - defaults to <literal>true</literal>): - Specifies that updates to this property do or do not require acquisition of the - optimistic lock. In other words, dertermines if a version increment should occur when + specifies that updates to this property do or do not require acquisition of the + optimistic lock. In other words, it determines if a version increment should occur when this property is dirty. </para> </callout> <callout arearefs="manytoone13"> <para> <literal>lazy</literal> (optional - defaults to <literal>proxy</literal>): - By default, single point associations are proxied. <literal>lazy="no-proxy"</literal> + by default, single point associations are proxied. <literal>lazy="no-proxy"</literal> specifies that the property should be fetched lazily when the instance variable - is first accessed (requires build-time bytecode instrumentation). + is first accessed. This requires build-time bytecode instrumentation. <literal>lazy="false"</literal> specifies that the association will always be eagerly fetched. </para> @@ -1836,13 +1839,13 @@ <callout arearefs="manytoone14"> <para> <literal>not-found</literal> (optional - defaults to <literal>exception</literal>): - Specifies how foreign keys that reference missing rows will be handled: + specifies how foreign keys that reference missing rows will be handled. <literal>ignore</literal> will treat a missing row as a null association. </para> </callout> <callout arearefs="manytoone15"> <para> - <literal>entity-name</literal> (optional): The entity name of the associated class. + <literal>entity-name</literal> (optional): the entity name of the associated class. </para> </callout> <callout arearefs="manytoone16"> @@ -1857,18 +1860,18 @@ <para> Setting a value of the <literal>cascade</literal> attribute to any meaningful value other than <literal>none</literal> will propagate certain operations to the - associated object. The meaningful values are the names of Hibernate's basic - operations, <literal>persist, merge, delete, save-update, evict, replicate, lock, - refresh</literal>, as well as the special values <literal>delete-orphan</literal> - and <literal>all</literal> and comma-separated combinations of operation - names, for example, <literal>cascade="persist,merge,evict"</literal> or + associated object. The meaningful values are divided into three categories. First, basic + operations, which include: <literal>persist, merge, delete, save-update, evict, replicate, lock and + refresh</literal>; second, special values: <literal>delete-orphan</literal>; + and third,<literal>all</literal> comma-separated combinations of operation + names: <literal>cascade="persist,merge,evict"</literal> or <literal>cascade="all,delete-orphan"</literal>. See <xref linkend="objectstate-transitive"/> - for a full explanation. Note that single valued associations (many-to-one and - one-to-one associations) do not support orphan delete. + for a full explanation. Note that single valued, many-to-one and + one-to-one, associations do not support orphan delete. </para> <para> - A typical <literal>many-to-one</literal> declaration looks as simple as this: + Here is an example of a typical <literal>many-to-one</literal> declaration: </para> <programlisting><![CDATA[<many-to-one name="product" class="Product" column="PRODUCT_ID"/>]]></programlisting> @@ -1876,10 +1879,10 @@ <para> The <literal>property-ref</literal> attribute should only be used for mapping legacy data where a foreign key refers to a unique key of the associated table other than - the primary key. This is an ugly relational model. For example, suppose the - <literal>Product</literal> class had a unique serial number, that is not the primary - key. (The <literal>unique</literal> attribute controls Hibernate's DDL generation with - the SchemaExport tool.) + the primary key. This is a complicated and confusing relational model. For example, if the + <literal>Product</literal> class had a unique serial number that is not the primary + key. The <literal>unique</literal> attribute controls Hibernate's DDL generation with + the SchemaExport tool. </para> <programlisting><![CDATA[<property name="serialNumber" unique="true" type="string" column="SERIAL_NUMBER"/>]]></programlisting> @@ -1891,7 +1894,7 @@ <programlisting><![CDATA[<many-to-one name="product" property-ref="serialNumber" column="PRODUCT_SERIAL_NUMBER"/>]]></programlisting> <para> - This is certainly not encouraged, however. + This is not encouraged, however. </para> <para> @@ -1900,7 +1903,7 @@ </para> <para> - If the referenced unique key is the property of a component, you may specify a property path: + If the referenced unique key is the property of a component, you can specify a property path: </para> <programlisting><![CDATA[<many-to-one name="owner" property-ref="identity.ssn" column="OWNER_SSN"/>]]></programlisting> @@ -1908,7 +1911,7 @@ </sect2> <sect2 id="mapping-declaration-onetoone" revision="3"> - <title>one-to-one</title> + <title>One-to-one</title> <para> A one-to-one association to another persistent class is declared using a @@ -1946,78 +1949,78 @@ <calloutlist> <callout arearefs="onetoone1"> <para> - <literal>name</literal>: The name of the property. + <literal>name</literal>: the name of the property. </para> </callout> <callout arearefs="onetoone2"> <para> <literal>class</literal> (optional - defaults to the property type - determined by reflection): The name of the associated class. + determined by reflection): the name of the associated class. </para> </callout> <callout arearefs="onetoone3"> <para> - <literal>cascade</literal> (optional) specifies which operations should + <literal>cascade</literal> (optional): specifies which operations should be cascaded from the parent object to the associated object. </para> </callout> <callout arearefs="onetoone4"> <para> - <literal>constrained</literal> (optional) specifies that a foreign key constraint - on the primary key of the mapped table references the table of the associated + <literal>constrained</literal> (optional): specifies that a foreign key constraint + on the primary key of the mapped table and references the table of the associated class. This option affects the order in which <literal>save()</literal> and <literal>delete()</literal> are cascaded, and determines whether the association - may be proxied (it is also used by the schema export tool). + can be proxied. It is also used by the schema export tool. </para> </callout> <callout arearefs="onetoone5"> <para> <literal>fetch</literal> (optional - defaults to <literal>select</literal>): - Chooses between outer-join fetching or sequential select fetching. + chooses between outer-join fetching or sequential select fetching. </para> </callout> <callout arearefs="onetoone6"> <para> - <literal>property-ref</literal>: (optional) The name of a property of the associated class + <literal>property-ref</literal> (optional): the name of a property of the associated class that is joined to the primary key of this class. If not specified, the primary key of the associated class is used. </para> </callout> <callout arearefs="onetoone7"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the property value. + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses for accessing the property value. </para> </callout> <callout arearefs="onetoone8"> <para> - <literal>formula</literal> (optional): Almost all one to one associations map to the - primary key of the owning entity. In the rare case that this is not the case, you may - specify a some other column, columns or expression to join on using an SQL formula. (See - <literal>org.hibernate.test.onetooneformula</literal> for an example.) + <literal>formula</literal> (optional): almost all one-to-one associations map to the + primary key of the owning entity. If this is not the case, you can + specify another column, columns or expression to join on using an SQL formula. See + <literal>org.hibernate.test.onetooneformula</literal> for an example. </para> </callout> <callout arearefs="onetoone9"> <para> <literal>lazy</literal> (optional - defaults to <literal>proxy</literal>): - By default, single point associations are proxied. <literal>lazy="no-proxy"</literal> + by default, single point associations are proxied. <literal>lazy="no-proxy"</literal> specifies that the property should be fetched lazily when the instance variable - is first accessed (requires build-time bytecode instrumentation). + is first accessed. It requires build-time bytecode instrumentation. <literal>lazy="false"</literal> specifies that the association will always be eagerly fetched. <emphasis>Note that if <literal>constrained="false"</literal>, - proxying is impossible and Hibernate will eager fetch the association!</emphasis> + proxying is impossible and Hibernate will eagerly fetch the association</emphasis>. </para> </callout> <callout arearefs="onetoone10"> <para> - <literal>entity-name</literal> (optional): The entity name of the associated class. + <literal>entity-name</literal> (optional): the entity name of the associated class. </para> </callout> </calloutlist> </programlistingco> <para> - There are two varieties of one-to-one association: + There are two varieties of one-to-one associations: </para> <itemizedlist> <listitem><para> @@ -2029,23 +2032,23 @@ </itemizedlist> <para> - Primary key associations don't need an extra table column; if two rows are related by - the association then the two table rows share the same primary key value. So if you want - two objects to be related by a primary key association, you must make sure that they - are assigned the same identifier value! + Primary key associations do not need an extra table column. If two rows are related by + the association, then the two table rows share the same primary key value. + To relate two objects by a primary key association, ensure that they + are assigned the same identifier value. </para> <para> For a primary key association, add the following mappings to <literal>Employee</literal> and - <literal>Person</literal>, respectively. + <literal>Person</literal> respectively: </para> <programlisting><![CDATA[<one-to-one name="person" class="Person"/>]]></programlisting> <programlisting><![CDATA[<one-to-one name="employee" class="Employee" constrained="true"/>]]></programlisting> <para> - Now we must ensure that the primary keys of related rows in the PERSON and - EMPLOYEE tables are equal. We use a special Hibernate identifier generation strategy + Ensure that the primary keys of the related rows in the PERSON and + EMPLOYEE tables are equal. You use a special Hibernate identifier generation strategy called <literal>foreign</literal>: </para> @@ -2062,20 +2065,20 @@ </class>]]></programlisting> <para> - A newly saved instance of <literal>Person</literal> is then assigned the same primary - key value as the <literal>Employee</literal> instance refered with the <literal>employee</literal> + A newly saved instance of <literal>Person</literal> is assigned the same primary + key value as the <literal>Employee</literal> instance referred with the <literal>employee</literal> property of that <literal>Person</literal>. </para> <para> Alternatively, a foreign key with a unique constraint, from <literal>Employee</literal> to - <literal>Person</literal>, may be expressed as: + <literal>Person</literal>, can be expressed as: </para> <programlisting><![CDATA[<many-to-one name="person" class="Person" column="PERSON_ID" unique="true"/>]]></programlisting> <para> - And this association may be made bidirectional by adding the following to the + This association can be made bidirectional by adding the following to the <literal>Person</literal> mapping: </para> @@ -2084,7 +2087,7 @@ </sect2> <sect2 id="mapping-declaration-naturalid"> - <title>natural-id</title> + <title>Natural-id</title> <programlisting><![CDATA[<natural-id mutable="true|false"/> <property ... /> @@ -2093,28 +2096,28 @@ </natural-id>]]></programlisting> <para> - Even though we recommend the use of surrogate keys as primary keys, you should still try + Although we recommend the use of surrogate keys as primary keys, you should try to identify natural keys for all entities. A natural key is a property or combination of - properties that is unique and non-null. If it is also immutable, even better. Map the + properties that is unique and non-null. It is also immutable. Map the properties of the natural key inside the <literal>&lt;natural-id&gt;</literal> element. - Hibernate will generate the necessary unique key and nullability constraints, and your + Hibernate will generate the necessary unique key and nullability constraints and, as a result, your mapping will be more self-documenting. </para> <para> - We strongly recommend that you implement <literal>equals()</literal> and + It is recommended that you implement <literal>equals()</literal> and <literal>hashCode()</literal> to compare the natural key properties of the entity. </para> <para> - This mapping is not intended for use with entities with natural primary keys. + This mapping is not intended for use with entities that have natural primary keys. </para> <itemizedlist spacing="compact"> <listitem> <para> - <literal>mutable</literal> (optional, defaults to <literal>false</literal>): - By default, natural identifier properties as assumed to be immutable (constant). + <literal>mutable</literal> (optional - defaults to <literal>false</literal>): + by default, natural identifier properties are assumed to be immutable (constant). </para> </listitem> </itemizedlist> @@ -2122,13 +2125,13 @@ </sect2> <sect2 id="mapping-declaration-component" revision="2"> - <title>component, dynamic-component</title> + <title>Component and dynamic-component</title> <para> The <literal>&lt;component&gt;</literal> element maps properties of a - child object to columns of the table of a parent class. Components may, in + child object to columns of the table of a parent class. Components can, in turn, declare their own properties, components or collections. See - "Components" below. + the "Component" examples below: </para> <programlistingco> @@ -2161,52 +2164,52 @@ <calloutlist> <callout arearefs="component1"> <para> - <literal>name</literal>: The name of the property. + <literal>name</literal>: the name of the property. </para> </callout> <callout arearefs="component2"> <para> <literal>class</literal> (optional - defaults to the property type - determined by reflection): The name of the component (child) class. + determined by reflection): the name of the component (child) class. </para> </callout> <callout arearefs="component3"> <para> - <literal>insert</literal>: Do the mapped columns appear in SQL - <literal>INSERT</literal>s? + <literal>insert</literal>: do the mapped columns appear in SQL + <literal>INSERTs</literal>? </para> </callout> <callout arearefs="component4"> <para> - <literal>update</literal>: Do the mapped columns appear in SQL - <literal>UPDATE</literal>s? + <literal>update</literal>: do the mapped columns appear in SQL + <literal>UPDATEs</literal>? </para> </callout> <callout arearefs="component5"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the property value. + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses for accessing the property value. </para> </callout> <callout arearefs="component6"> <para> - <literal>lazy</literal> (optional - defaults to <literal>false</literal>): Specifies + <literal>lazy</literal> (optional - defaults to <literal>false</literal>): specifies that this component should be fetched lazily when the instance variable is first - accessed (requires build-time bytecode instrumentation). + accessed. It requires build-time bytecode instrumentation. </para> </callout> <callout arearefs="component7"> <para> <literal>optimistic-lock</literal> (optional - defaults to <literal>true</literal>): - Specifies that updates to this component do or do not require acquisition of the - optimistic lock. In other words, determines if a version increment should occur when + specifies that updates to this component either do or do not require acquisition of the + optimistic lock. It determines if a version increment should occur when this property is dirty. </para> </callout> <callout arearefs="component8"> <para> <literal>unique</literal> (optional - defaults to <literal>false</literal>): - Specifies that a unique constraint exists upon all mapped columns of the + specifies that a unique constraint exists upon all mapped columns of the component. </para> </callout> @@ -2226,21 +2229,21 @@ <para> The <literal>&lt;dynamic-component&gt;</literal> element allows a <literal>Map</literal> - to be mapped as a component, where the property names refer to keys of the map, see - <xref linkend="components-dynamic"/>. + to be mapped as a component, where the property names refer to keys of the map. See + <xref linkend="components-dynamic"/> for more information. </para> </sect2> <sect2 id="mapping-declaration-properties" revision="2"> - <title>properties</title> + <title>Properties</title> <para> The <literal>&lt;properties&gt;</literal> element allows the definition of a named, - logical grouping of properties of a class. The most important use of the construct + logical grouping of the properties of a class. The most important use of the construct is that it allows a combination of properties to be the target of a <literal>property-ref</literal>. It is also a convenient way to define a multi-column - unique constraint. + unique constraint. For example: </para> <programlistingco> @@ -2266,34 +2269,34 @@ <calloutlist> <callout arearefs="properties1"> <para> - <literal>name</literal>: The logical name of the grouping - + <literal>name</literal>: the logical name of the grouping. It is <emphasis>not</emphasis> an actual property name. </para> </callout> <callout arearefs="properties2"> <para> - <literal>insert</literal>: Do the mapped columns appear in SQL - <literal>INSERT</literal>s? + <literal>insert</literal>: do the mapped columns appear in SQL + <literal>INSERTs</literal>? </para> </callout> <callout arearefs="properties3"> <para> - <literal>update</literal>: Do the mapped columns appear in SQL - <literal>UPDATE</literal>s? + <literal>update</literal>: do the mapped columns appear in SQL + <literal>UPDATEs</literal>? </para> - </callout> + </callout>n <callout arearefs="properties4"> <para> <literal>optimistic-lock</literal> (optional - defaults to <literal>true</literal>): - Specifies that updates to these properties do or do not require acquisition of the - optimistic lock. In other words, determines if a version increment should occur when + specifies that updates to these properties either do or do not require acquisition of the + optimistic lock. It determines if a version increment should occur when these properties are dirty. </para> </callout> <callout arearefs="properties5"> <para> <literal>unique</literal> (optional - defaults to <literal>false</literal>): - Specifies that a unique constraint exists upon all mapped columns of the + specifies that a unique constraint exists upon all mapped columns of the component. </para> </callout> @@ -2306,6 +2309,7 @@ <programlisting><![CDATA[<class name="Person"> <id name="personNumber"/> + ... <properties name="name" unique="true" update="false"> @@ -2316,7 +2320,7 @@ </class>]]></programlisting> <para> - Then we might have some legacy data association which refers to this unique key of + You might have some legacy data association that refers to this unique key of the <literal>Person</literal> table, instead of to the primary key: </para> @@ -2328,19 +2332,19 @@ </many-to-one>]]></programlisting> <para> - We don't recommend the use of this kind of thing outside the context of mapping - legacy data. + The use of this outside the context of mapping + legacy data is not recommended. </para> </sect2> <sect2 id="mapping-declaration-subclass" revision="4"> - <title>subclass</title> + <title>Subclass</title> <para> - Finally, polymorphic persistence requires the declaration of each subclass of + Polymorphic persistence requires the declaration of each subclass of the root persistent class. For the table-per-class-hierarchy - mapping strategy, the <literal>&lt;subclass&gt;</literal> declaration is used. + mapping strategy, the <literal>&lt;subclass&gt;</literal> declaration is used. For example: </para> <programlistingco> @@ -2367,24 +2371,24 @@ <calloutlist> <callout arearefs="subclass1"> <para> - <literal>name</literal>: The fully qualified class name of the subclass. + <literal>name</literal>: the fully qualified class name of the subclass. </para> </callout> <callout arearefs="subclass2"> <para> - <literal>discriminator-value</literal> (optional - defaults to the class name): A - value that distiguishes individual subclasses. + <literal>discriminator-value</literal> (optional - defaults to the class name): a + value that distinguishes individual subclasses. </para> </callout> <callout arearefs="subclass3"> <para> - <literal>proxy</literal> (optional): Specifies a class or interface to use for + <literal>proxy</literal> (optional): specifies a class or interface used for lazy initializing proxies. </para> </callout> <callout arearefs="subclass4"> <para> - <literal>lazy</literal> (optional, defaults to <literal>true</literal>): Setting + <literal>lazy</literal> (optional - defaults to <literal>true</literal>): setting <literal>lazy="false"</literal> disables the use of lazy fetching. </para> </callout> @@ -2392,26 +2396,26 @@ </programlistingco> <para> - Each subclass should declare its own persistent properties and subclasses. + Each subclass declares its own persistent properties and subclasses. <literal>&lt;version&gt;</literal> and <literal>&lt;id&gt;</literal> properties - are assumed to be inherited from the root class. Each subclass in a heirarchy must - define a unique <literal>discriminator-value</literal>. If none is specified, the + are assumed to be inherited from the root class. Each subclass in a hierarchy must + define a unique <literal>discriminator-value</literal>. If this is not specified, the fully qualified Java class name is used. </para> <para> - For information about inheritance mappings, see <xref linkend="inheritance"/>. + For information about inheritance mappings see <xref linkend="inheritance"/>. </para> </sect2> <sect2 id="mapping-declaration-joinedsubclass" revision="3"> - <title>joined-subclass</title> + <title>Joined-subclass</title> <para> - Alternatively, each subclass may be mapped to its own table (table-per-subclass - mapping strategy). Inherited state is retrieved by joining with the table of the - superclass. We use the <literal>&lt;joined-subclass&gt;</literal> element. + Each subclass can also be mapped to its own table. This is called the table-per-subclass + mapping strategy. An inherited state is retrieved by joining with the table of the + superclass. To do this you use the <literal>&lt;joined-subclass&gt;</literal> element. For example: </para> <programlistingco> @@ -2444,23 +2448,23 @@ <calloutlist> <callout arearefs="joinedsubclass1"> <para> - <literal>name</literal>: The fully qualified class name of the subclass. + <literal>name</literal>: the fully qualified class name of the subclass. </para> </callout> <callout arearefs="joinedsubclass2"> <para> - <literal>table</literal>: The name of the subclass table. + <literal>table</literal>: the name of the subclass table. </para> </callout> <callout arearefs="joinedsubclass3"> <para> - <literal>proxy</literal> (optional): Specifies a class or interface to use + <literal>proxy</literal> (optional): specifies a class or interface to use for lazy initializing proxies. </para> </callout> <callout arearefs="joinedsubclass4"> <para> - <literal>lazy</literal> (optional, defaults to <literal>true</literal>): Setting + <literal>lazy</literal> (optional, defaults to <literal>true</literal>): setting <literal>lazy="false"</literal> disables the use of lazy fetching. </para> </callout> @@ -2468,10 +2472,10 @@ </programlistingco> <para> - No discriminator column is required for this mapping strategy. Each subclass must, + A discriminator column is not required for this mapping strategy. Each subclass must, however, declare a table column holding the object identifier using the <literal>&lt;key&gt;</literal> element. The mapping at the start of the chapter - would be re-written as: + would then be re-written as: </para> <programlisting><![CDATA[<?xml version="1.0"?> @@ -2507,23 +2511,23 @@ </hibernate-mapping>]]></programlisting> <para> - For information about inheritance mappings, see <xref linkend="inheritance"/>. + For information about inheritance mappings see <xref linkend="inheritance"/>. </para> </sect2> <sect2 id="mapping-declaration-unionsubclass" revision="2"> - <title>union-subclass</title> + <title>Union-subclass</title> <para> A third option is to map only the concrete classes of an inheritance hierarchy - to tables, (the table-per-concrete-class strategy) where each table defines all - persistent state of the class, including inherited state. In Hibernate, it is - not absolutely necessary to explicitly map such inheritance hierarchies. You - can simply map each class with a separate <literal>&lt;class&gt;</literal> + to tables. This is called the table-per-concrete-class strategy. Each table defines all + persistent states of the class, including the inherited state. In Hibernate, it is + not necessary to explicitly map such inheritance hierarchies. You + can map each class with a separate <literal>&lt;class&gt;</literal> declaration. However, if you wish use polymorphic associations (e.g. an association to the superclass of your hierarchy), you need to - use the <literal>&lt;union-subclass&gt;</literal> mapping. + use the <literal>&lt;union-subclass&gt;</literal> mapping. For example: </para> <programlistingco> @@ -2555,23 +2559,23 @@ <calloutlist> <callout arearefs="unionsubclass1"> <para> - <literal>name</literal>: The fully qualified class name of the subclass. + <literal>name</literal>: the fully qualified class name of the subclass. </para> </callout> <callout arearefs="unionsubclass2"> <para> - <literal>table</literal>: The name of the subclass table. + <literal>table</literal>: the name of the subclass table. </para> </callout> <callout arearefs="unionsubclass3"> <para> - <literal>proxy</literal> (optional): Specifies a class or interface to use + <literal>proxy</literal> (optional): specifies a class or interface to use for lazy initializing proxies. </para> </callout> <callout arearefs="unionsubclass4"> <para> - <literal>lazy</literal> (optional, defaults to <literal>true</literal>): Setting + <literal>lazy</literal> (optional, defaults to <literal>true</literal>): setting <literal>lazy="false"</literal> disables the use of lazy fetching. </para> </callout> @@ -2583,17 +2587,17 @@ </para> <para> - For information about inheritance mappings, see <xref linkend="inheritance"/>. + For information about inheritance mappings see <xref linkend="inheritance"/>. </para> </sect2> <sect2 id="mapping-declaration-join" revision="3"> - <title>join</title> + <title>Join</title> <para> Using the <literal>&lt;join&gt;</literal> element, it is possible to map - properties of one class to several tables, when there's a 1-to-1 relationship between the tables. + properties of one class to several tables that have a one-to-one relationship. For example: </para> <programlistingco> @@ -2622,30 +2626,30 @@ <calloutlist> <callout arearefs="join1"> <para> - <literal>table</literal>: The name of the joined table. + <literal>table</literal>: the name of the joined table. </para> </callout> <callout arearefs="join2"> <para> - <literal>schema</literal> (optional): Override the schema name specified by + <literal>schema</literal> (optional): overrides the schema name specified by the root <literal>&lt;hibernate-mapping&gt;</literal> element. </para> </callout> <callout arearefs="join3"> <para> - <literal>catalog</literal> (optional): Override the catalog name specified by + <literal>catalog</literal> (optional): overrides the catalog name specified by the root <literal>&lt;hibernate-mapping&gt;</literal> element. </para> </callout> <callout arearefs="join4"> <para> <literal>fetch</literal> (optional - defaults to <literal>join</literal>): - If set to <literal>join</literal>, the default, Hibernate will use an inner join - to retrieve a <literal>&lt;join&gt;</literal> defined by a class or its superclasses - and an outer join for a <literal>&lt;join&gt;</literal> defined by a subclass. + if set to <literal>join</literal>, the default, Hibernate will use an inner join + to retrieve a <literal>&lt;join&gt;</literal> defined by a class or its superclasses. It will use + an outer join for a <literal>&lt;join&gt;</literal> defined by a subclass. If set to <literal>select</literal> then Hibernate will use a sequential select for - a <literal>&lt;join&gt;</literal> defined on a subclass, which will be issued only - if a row turns out to represent an instance of the subclass. Inner joins will still + a <literal>&lt;join&gt;</literal> defined on a subclass. This will be issued only + if a row represents an instance of the subclass. Inner joins will still be used to retrieve a <literal>&lt;join&gt;</literal> defined by the class and its superclasses. </para> @@ -2653,23 +2657,23 @@ <callout arearefs="join5"> <para> <literal>inverse</literal> (optional - defaults to <literal>false</literal>): - If enabled, Hibernate will not try to insert or update the properties defined + if enabled, Hibernate will not insert or update the properties defined by this join. </para> </callout> <callout arearefs="join6"> <para> <literal>optional</literal> (optional - defaults to <literal>false</literal>): - If enabled, Hibernate will insert a row only if the properties defined by this - join are non-null and will always use an outer join to retrieve the properties. + if enabled, Hibernate will insert a row only if the properties defined by this + join are non-null. It will always use an outer join to retrieve the properties. </para> </callout> </calloutlist> </programlistingco> <para> - For example, the address information for a person can be mapped to a separate - table (while preserving value type semantics for all properties): + For example, address information for a person can be mapped to a separate + table while preserving value type semantics for all properties: </para> <programlisting><![CDATA[<class name="Person" @@ -2686,7 +2690,7 @@ ...]]></programlisting> <para> - This feature is often only useful for legacy data models, we recommend fewer + This feature is often only useful for legacy data models. We recommend fewer tables than classes and a fine-grained domain model. However, it is useful for switching between inheritance mapping strategies in a single hierarchy, as explained later. @@ -2695,13 +2699,13 @@ </sect2> <sect2 id="mapping-declaration-key"> - <title>key</title> + <title>Key</title> - <para> - We've seen the <literal>&lt;key&gt;</literal> element crop up a few times - now. It appears anywhere the parent mapping element defines a join to - a new table, and defines the foreign key in the joined table, that references - the primary key of the original table. + <para> + The <literal>&lt;key&gt;</literal> element has featured a few times within this guide. + It appears anywhere the parent mapping element defines a join to + a new table that references + the primary key of the original table. It also defines the foreign key in the joined table: </para> <programlistingco> @@ -2709,7 +2713,7 @@ <area id="key1" coords="2 50"/> <area id="key2" coords="3 50"/> <area id="key3" coords="4 50"/> - <area id="key4" coords="5 50"/> + <area id="key4" coords="5 50"/> <area id="key5" coords="6 50"/> <area id="key6" coords="7 50"/> </areaspec> @@ -2725,51 +2729,51 @@ <calloutlist> <callout arearefs="key1"> <para> - <literal>column</literal> (optional): The name of the foreign key column. - This may also be specified by nested <literal>&lt;column&gt;</literal> + <literal>column</literal> (optional): the name of the foreign key column. + This can also be specified by nested <literal>&lt;column&gt;</literal> element(s). </para> </callout> <callout arearefs="key2"> <para> - <literal>on-delete</literal> (optional, defaults to <literal>noaction</literal>): - Specifies whether the foreign key constraint has database-level cascade delete + <literal>on-delete</literal> (optional - defaults to <literal>noaction</literal>): + specifies whether the foreign key constraint has database-level cascade delete enabled. </para> </callout> <callout arearefs="key3"> <para> - <literal>property-ref</literal> (optional): Specifies that the foreign key refers - to columns that are not the primary key of the orginal table. (Provided for - legacy data.) + <literal>property-ref</literal> (optional): specifies that the foreign key refers + to columns that are not the primary key of the original table. It is provided for + legacy data. </para> </callout> <callout arearefs="key4"> <para> - <literal>not-null</literal> (optional): Specifies that the foreign key columns - are not nullable (this is implied whenever the foreign key is also part of the - primary key). + <literal>not-null</literal> (optional): specifies that the foreign key columns + are not nullable. This is implied whenever the foreign key is also part of the + primary key. </para> </callout> <callout arearefs="key5"> <para> - <literal>update</literal> (optional): Specifies that the foreign key should never - be updated (this is implied whenever the foreign key is also part of the primary - key). + <literal>update</literal> (optional): specifies that the foreign key should never + be updated. This is implied whenever the foreign key is also part of the primary + key. </para> </callout> - <callout arearefs="key6"> + <callout arearefs="key6">file:///usr/share/doc/HTML/en-US/index.html <para> - <literal>unique</literal> (optional): Specifies that the foreign key should have - a unique constraint (this is implied whenever the foreign key is also the primary key). + <literal>unique</literal> (optional): specifies that the foreign key should have + a unique constraint. This is implied whenever the foreign key is also the primary key. </para> </callout> </calloutlist> </programlistingco> <para> - We recommend that for systems where delete performance is important, all keys should be - defined <literal>on-delete="cascade"</literal>, and Hibernate will use a database-level + For systems where delete performance is important, we recommend that all keys should be + defined <literal>on-delete="cascade"</literal>. Hibernate uses a database-level <literal>ON CASCADE DELETE</literal> constraint, instead of many individual <literal>DELETE</literal> statements. Be aware that this feature bypasses Hibernate's usual optimistic locking strategy for versioned data. @@ -2777,7 +2781,7 @@ <para> The <literal>not-null</literal> and <literal>update</literal> attributes are useful when - mapping a unidirectional one to many association. If you map a unidirectional one to many + mapping a unidirectional one-to-many association. If you map a unidirectional one-to-many association to a non-nullable foreign key, you <emphasis>must</emphasis> declare the key column using <literal>&lt;key not-null="true"&gt;</literal>. </para> @@ -2785,11 +2789,11 @@ </sect2> <sect2 id="mapping-column" revision="4"> - <title>column and formula elements</title> + <title>Column and formula elements</title> <para> - Any mapping element which accepts a <literal>column</literal> attribute will alternatively + Mapping elements which accept a <literal>column</literal> attribute will alternatively accept a <literal>&lt;column&gt;</literal> subelement. Likewise, <literal>&lt;formula&gt;</literal> - is an alternative to the <literal>formula</literal> attribute. + is an alternative to the <literal>formula</literal> attribute. For example: </para> <programlisting><![CDATA[<column @@ -2808,7 +2812,7 @@ <programlisting><![CDATA[<formula>SQL expression</formula>]]></programlisting> <para> - <literal>column</literal> and <literal>formula</literal> attributes may even be combined + <literal>column</literal> and <literal>formula</literal> attributes can even be combined within the same property or association mapping to express, for example, exotic join conditions. </para> @@ -2822,13 +2826,13 @@ </sect2> <sect2 id="mapping-declaration-import"> - <title>import</title> + <title>Import</title> <para> - Suppose your application has two persistent classes with the same name, and you don't want to - specify the fully qualified (package) name in Hibernate queries. Classes may be "imported" - explicitly, rather than relying upon <literal>auto-import="true"</literal>. You may even import - classes and interfaces that are not explicitly mapped. + If your application has two persistent classes with the same name, and you do not want to + specify the fully qualified package name in Hibernate queries, classes can be "imported" + explicitly, rather than relying upon <literal>auto-import="true"</literal>. You can also import + classes and interfaces that are not explicitly mapped: </para> <programlisting><![CDATA[<import class="java.lang.Object" rename="Universe"/>]]></programlisting> @@ -2845,13 +2849,13 @@ <calloutlist> <callout arearefs="import1"> <para> - <literal>class</literal>: The fully qualified class name of of any Java class. + <literal>class</literal>: the fully qualified class name of any Java class. </para> </callout> <callout arearefs="import2"> <para> <literal>rename</literal> (optional - defaults to the unqualified class name): - A name that may be used in the query language. + a name that can be used in the query language. </para> </callout> </calloutlist> @@ -2860,21 +2864,21 @@ </sect2> <sect2 id="mapping-types-anymapping" revision="2"> - <title>any</title> + <title>Any</title> <para> - There is one further type of property mapping. The <literal>&lt;any&gt;</literal> mapping element - defines a polymorphic association to classes from multiple tables. This type of mapping always - requires more than one column. The first column holds the type of the associated entity. - The remaining columns hold the identifier. It is impossible to specify a foreign key constraint - for this kind of association, so this is most certainly not meant as the usual way of mapping - (polymorphic) associations. You should use this only in very special cases (eg. audit logs, - user session data, etc). + There is one more type of property mapping. The <literal>&lt;any&gt;</literal> mapping element + defines a polymorphic association to classes from multiple tables. This type of mapping + requires more than one column. The first column contains the type of the associated entity. + The remaining columns contain the identifier. It is impossible to specify a foreign key constraint + for this kind of association. This is not the usual way of mapping + polymorphic associations and you should use this only in special cases. For example, for audit logs, + user session data, etc. </para> <para> - The <literal>meta-type</literal> attribute lets the application specify a custom type that - maps database column values to persistent classes which have identifier properties of the + The <literal>meta-type</literal> attribute allows the application to specify a custom type that + maps database column values to persistent classes that have identifier properties of the type specified by <literal>id-type</literal>. You must specify the mapping from values of the meta-type to class names. </para> @@ -2925,7 +2929,7 @@ <callout arearefs="any3"> <para> <literal>meta-type</literal> (optional - defaults to <literal>string</literal>): - Any type that is allowed for a discriminator mapping. + any type that is allowed for a discriminator mapping. </para> </callout> <callout arearefs="any4"> @@ -2936,15 +2940,15 @@ </callout> <callout arearefs="any5"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the property value. - </para> + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses for accessing the property value. + </para>file:///usr/share/doc/HTML/en-US/index.html </callout> <callout arearefs="any6"> <para> <literal>optimistic-lock</literal> (optional - defaults to <literal>true</literal>): - Specifies that updates to this property do or do not require acquisition of the - optimistic lock. In other words, define if a version increment should occur if this + specifies that updates to this property either do or do not require acquisition of the + optimistic lock. It defines whether a version increment should occur if this property is dirty. </para> </callout> @@ -2956,71 +2960,71 @@ </sect1> <sect1 id="mapping-types"> - <title>Hibernate Types</title> + <title>Hibernate types</title> <sect2 id="mapping-types-entitiesvalues" revision="1"> <title>Entities and values</title> <para> - To understand the behaviour of various Java language-level objects with respect - to the persistence service, we need to classify them into two groups: + In relation to the persistence service, Java language-level objects are classified + into two groups: </para> <para> An <emphasis>entity</emphasis> exists independently of any other objects holding - references to the entity. Contrast this with the usual Java model where an + references to the entity. Contrast this with the usual Java model, where an unreferenced object is garbage collected. Entities must be explicitly saved and - deleted (except that saves and deletions may be <emphasis>cascaded</emphasis> - from a parent entity to its children). This is different from the ODMG model of - object persistence by reachablity - and corresponds more closely to how + deleted. Saves and deletions, however, can be <emphasis>cascaded</emphasis> + from a parent entity to its children. This is different from the ODMG model of + object persistence by reachability and corresponds more closely to how application objects are usually used in large systems. Entities support - circular and shared references. They may also be versioned. + circular and shared references. They can also be versioned. </para> <para> An entity's persistent state consists of references to other entities and - instances of <emphasis>value</emphasis> types. Values are primitives, - collections (not what's inside a collection), components and certain immutable - objects. Unlike entities, values (in particular collections and components) + instances of <emphasis>value</emphasis> types. Values are primitives: + collections (not what is inside a collection), components and certain immutable + objects. Unlike entities, values in particular collections and components, <emphasis>are</emphasis> persisted and deleted by reachability. Since value - objects (and primitives) are persisted and deleted along with their containing - entity they may not be independently versioned. Values have no independent + objects and primitives are persisted and deleted along with their containing + entity, they cannot be independently versioned. Values have no independent identity, so they cannot be shared by two entities or collections. </para> <para> - Up until now, we've been using the term "persistent class" to refer to - entities. We will continue to do that. Strictly speaking, however, not all - user-defined classes with persistent state are entities. A - <emphasis>component</emphasis> is a user defined class with value semantics. + Until now, we have been using the term "persistent class" to refer to + entities. We will continue to do that. Not all + user-defined classes with a persistent state, however, are entities. A + <emphasis>component</emphasis> is a user-defined class with value semantics. A Java property of type <literal>java.lang.String</literal> also has value - semantics. Given this definition, we can say that all types (classes) provided - by the JDK have value type semantics in Java, while user-defined types may + semantics. Given this definition, all types (classes) provided + by the JDK have value type semantics in Java, while user-defined types can be mapped with entity or value type semantics. This decision is up to the - application developer. A good hint for an entity class in a domain model are + application developer. An entity class in a domain model will normally have shared references to a single instance of that class, while composition or aggregation usually translates to a value type. </para> <para> - We'll revisit both concepts throughout the documentation. + We will revisit both concepts throughout this reference guide. </para> <para> - The challenge is to map the Java type system (and the developers' definition of - entities and value types) to the SQL/database type system. The bridge between - both systems is provided by Hibernate: for entities we use - <literal>&lt;class&gt;</literal>, <literal>&lt;subclass&gt;</literal> and so on. + The challenge is to map the Java type system, and the developers' definition of + entities and value types, to the SQL/database type system. The bridge between + both systems is provided by Hibernate. For entities, + <literal>&lt;class&gt;</literal>, <literal>&lt;subclass&gt;</literal> and so on are used. For value types we use <literal>&lt;property&gt;</literal>, - <literal>&lt;component&gt;</literal>, etc, usually with a <literal>type</literal> + <literal>&lt;component&gt;</literal>etc., that usually have a <literal>type</literal> attribute. The value of this attribute is the name of a Hibernate - <emphasis>mapping type</emphasis>. Hibernate provides many mappings (for standard - JDK value types) out of the box. You can write your own mapping types and implement your - custom conversion strategies as well, as you'll see later. + <emphasis>mapping type</emphasis>. Hibernate provides a range of mappings for standard + JDK value types out of the box. You can write your own mapping types and implement your own + custom conversion strategies. </para> <para> - All built-in Hibernate types except collections support null semantics. + With the exception of collections, all built-in Hibernate types support null semantics. </para> </sect2> @@ -3029,7 +3033,7 @@ <title>Basic value types</title> <para> - The built-in <emphasis>basic mapping types</emphasis> may be roughly categorized into + The built-in <emphasis>basic mapping types</emphasis> can be roughly categorized into the following: <variablelist> <varlistentry> @@ -3129,7 +3133,7 @@ <listitem> <para> Maps serializable Java types to an appropriate SQL binary type. You - may also indicate the Hibernate type <literal>serializable</literal> with + can also indicate the Hibernate type <literal>serializable</literal> with the name of a serializable Java class or interface that does not default to a basic type. </para> @@ -3140,9 +3144,9 @@ <listitem> <para> Type mappings for the JDBC classes <literal>java.sql.Clob</literal> and - <literal>java.sql.Blob</literal>. These types may be inconvenient for some - applications, since the blob or clob object may not be reused outside of - a transaction. (Furthermore, driver support is patchy and inconsistent.) + <literal>java.sql.Blob</literal>. These types can be inconvenient for some + applications, since the blob or clob object cannot be reused outside of + a transaction. Driver support is patchy and inconsistent. </para> </listitem> </varlistentry> @@ -3153,13 +3157,13 @@ </term> <listitem> <para> - Type mappings for what are usually considered mutable Java types, where + Type mappings for what are considered mutable Java types. This is where Hibernate makes certain optimizations appropriate only for immutable Java types, and the application treats the object as immutable. For example, you should not call <literal>Date.setTime()</literal> for an instance mapped as <literal>imm_timestamp</literal>. To change the value of the property, and have that change made persistent, the - application must assign a new (nonidentical) object to the property. + application must assign a new, nonidentical, object to the property. </para> </listitem> </varlistentry> @@ -3168,9 +3172,9 @@ </para> <para> - Unique identifiers of entities and collections may be of any basic type except + Unique identifiers of entities and collections can be of any basic type except <literal>binary</literal>, <literal>blob</literal> and <literal>clob</literal>. - (Composite identifiers are also allowed, see below.) + Composite identifiers are also allowed. See below for more information. </para> <para> @@ -3188,7 +3192,7 @@ It is relatively easy for developers to create their own value types. For example, you might want to persist properties of type <literal>java.lang.BigInteger</literal> to <literal>VARCHAR</literal> columns. Hibernate does not provide a built-in type - for this. But custom types are not limited to mapping a property (or collection element) + for this. Custom types are not limited to mapping a property, or collection element, to a single table column. So, for example, you might have a Java property <literal>getName()</literal>/<literal>setName()</literal> of type <literal>java.lang.String</literal> that is persisted to the columns @@ -3198,7 +3202,7 @@ <para> To implement a custom type, implement either <literal>org.hibernate.UserType</literal> or <literal>org.hibernate.CompositeUserType</literal> and declare properties using the - fully qualified classname of the type. Check out + fully qualified classname of the type. View <literal>org.hibernate.test.DoubleStringType</literal> to see the kind of things that are possible. </para> @@ -3220,7 +3224,7 @@ </para> <para> - You may even supply parameters to a <literal>UserType</literal> in the mapping file. To + You can even supply parameters to a <literal>UserType</literal> in the mapping file. To do this, your <literal>UserType</literal> must implement the <literal>org.hibernate.usertype.ParameterizedType</literal> interface. To supply parameters to your custom type, you can use the <literal>&lt;type&gt;</literal> element in your mapping @@ -3239,9 +3243,9 @@ </para> <para> - If you use a certain <literal>UserType</literal> very often, it may be useful to define a + If you regularly use a certain <literal>UserType</literal>, it is useful to define a shorter name for it. You can do this using the <literal>&lt;typedef&gt;</literal> element. - Typedefs assign a name to a custom type, and may also contain a list of default + Typedefs assign a name to a custom type, and can also contain a list of default parameter values if the type is parameterized. </para> @@ -3258,13 +3262,13 @@ <para> Even though Hibernate's rich range of built-in types and support for components means you - will very rarely <emphasis>need</emphasis> to use a custom type, it is nevertheless - considered good form to use custom types for (non-entity) classes that occur frequently + will rarely need to use a custom type, it is + considered good practice to use custom types for non-entity classes that occur frequently in your application. For example, a <literal>MonetaryAmount</literal> class is a good - candidate for a <literal>CompositeUserType</literal>, even though it could easily be mapped - as a component. One motivation for this is abstraction. With a custom type, your mapping - documents would be future-proofed against possible changes in your way of representing - monetary values. + candidate for a <literal>CompositeUserType</literal>, even though it could be mapped + as a component. One reason for this is abstraction. With a custom type, your mapping + documents would be protected against changes to the way + monetary values are represented. </para> </sect2> @@ -3275,8 +3279,8 @@ <title>Mapping a class more than once</title> <para> It is possible to provide more than one mapping for a particular persistent class. In this - case you must specify an <emphasis>entity name</emphasis> do disambiguate between instances - of the two mapped entities. (By default, the entity name is the same as the class name.) + case, you must specify an <emphasis>entity name</emphasis> to disambiguate between instances + of the two mapped entities. By default, the entity name is the same as the class name. Hibernate lets you specify the entity name when working with persistent objects, when writing queries, or when mapping associations to the named entity. </para> @@ -3300,7 +3304,7 @@ </class>]]></programlisting> <para> - Notice how associations are now specified using <literal>entity-name</literal> instead of + Associations are now specified using <literal>entity-name</literal> instead of <literal>class</literal>. </para> @@ -3309,10 +3313,10 @@ <sect1 id="mapping-quotedidentifiers"> <title>SQL quoted identifiers</title> <para> - You may force Hibernate to quote an identifier in the generated SQL by enclosing the table or + You can force Hibernate to quote an identifier in the generated SQL by enclosing the table or column name in backticks in the mapping document. Hibernate will use the correct quotation - style for the SQL <literal>Dialect</literal> (usually double quotes, but brackets for SQL - Server and backticks for MySQL). + style for the SQL <literal>Dialect</literal>. This is usually double quotes, but the SQL + Server uses brackets and MySQL uses backticks. </para> <programlisting><![CDATA[<class name="LineItem" table="`Line Item`"> @@ -3328,7 +3332,7 @@ <title>Metadata alternatives</title> <para> - XML isn't for everyone, and so there are some alternative ways to define O/R mapping metadata in Hibernate. + XML does not suit all users so there are some alternative ways to define O/R mapping metadata in Hibernate. </para> <sect2 id="mapping-xdoclet"> @@ -3336,9 +3340,9 @@ <para> Many Hibernate users prefer to embed mapping information directly in sourcecode using - XDoclet <literal&gt;(a)hibernate.tags&lt;/literal&gt;. We will not cover this approach in this - document, since strictly it is considered part of XDoclet. However, we include the - following example of the <literal>Cat</literal> class with XDoclet mappings. + XDoclet <literal&gt;(a)hibernate.tags&lt;/literal&gt;. We do not cover this approach in this + reference guide since it is considered part of XDoclet. However, we include the + following example of the <literal>Cat</literal> class with XDoclet mappings: </para> <programlisting><![CDATA[package eg; @@ -3447,7 +3451,7 @@ }]]></programlisting> <para> - See the Hibernate web site for more examples of XDoclet and Hibernate. + See the Hibernate website for more examples of XDoclet and Hibernate. </para> </sect2> @@ -3456,14 +3460,14 @@ <title>Using JDK 5.0 Annotations</title> <para> - JDK 5.0 introduced XDoclet-style annotations at the language level, type-safe and - checked at compile time. This mechnism is more powerful than XDoclet annotations and + JDK 5.0 introduced XDoclet-style annotations at the language level that are type-safe and + checked at compile time. This mechanism is more powerful than XDoclet annotations and better supported by tools and IDEs. IntelliJ IDEA, for example, supports auto-completion and syntax highlighting of JDK 5.0 annotations. The new revision of the EJB specification (JSR-220) uses JDK 5.0 annotations as the primary metadata mechanism for entity beans. - Hibernate3 implements the <literal>EntityManager</literal> of JSR-220 (the persistence API), - support for mapping metadata is available via the <emphasis>Hibernate Annotations</emphasis> - package, as a separate download. Both EJB3 (JSR-220) and Hibernate3 metadata is supported. + Hibernate3 implements the <literal>EntityManager</literal> of JSR-220 (the persistence API). + Support for mapping metadata is available via the <emphasis>Hibernate Annotations</emphasis> + package as a separate download. Both EJB3 (JSR-220) and Hibernate3 metadata is supported. </para> <para> @@ -3493,63 +3497,66 @@ // Getter/setter and business methods }]]></programlisting> - <para> - Note that support for JDK 5.0 Annotations (and JSR-220) is still work in progress and - not completed. Please refer to the Hibernate Annotations module for more details. + <note> + <title>Note</title> + <para> + Support for JDK 5.0 Annotations (and JSR-220) is currently under development. + Please refer to the Hibernate Annotations module for more details. </para> + </note> </sect2> </sect1> <sect1 id="mapping-generated" revision="1"> - <title>Generated Properties</title> + <title>Generated properties</title> <para> - Generated properties are properties which have their values generated by the + Generated properties are properties that have their values generated by the database. Typically, Hibernate applications needed to <literal>refresh</literal> - objects which contain any properties for which the database was generating values. + objects that contain any properties for which the database was generating values. Marking properties as generated, however, lets the application delegate this - responsibility to Hibernate. Essentially, whenever Hibernate issues an SQL INSERT - or UPDATE for an entity which has defined generated properties, it immediately + responsibility to Hibernate. When Hibernate issues an SQL INSERT + or UPDATE for an entity that has defined generated properties, it immediately issues a select afterwards to retrieve the generated values. </para> <para> Properties marked as generated must additionally be non-insertable and non-updateable. Only <link linkend="mapping-declaration-version">versions</link>, <link linkend="mapping-declaration-timestamp">timestamps</link>, and - <link linkend="mapping-declaration-property">simple properties</link> can be marked as + <link linkend="mapping-declaration-property">simple properties</link>, can be marked as generated. </para> <para> - <literal>never</literal> (the default) - means that the given property value + <literal>never</literal> (the default): the given property value is not generated within the database. </para> <para> - <literal>insert</literal> - states that the given property value is generated on - insert, but is not regenerated on subsequent updates. Things like created-date would - fall into this category. Note that even thought + <literal>insert</literal>: the given property value is generated on + insert, but is not regenerated on subsequent updates. Properties like created-date + fall into this category. Even though <link linkend="mapping-declaration-version">version</link> and <link linkend="mapping-declaration-timestamp">timestamp</link> properties can - be marked as generated, this option is not available there... + be marked as generated, this option is not available. </para> <para> - <literal>always</literal> - states that the property value is generated both + <literal>always</literal>: the property value is generated both on insert and on update. </para> </sect1> <sect1 id="mapping-database-object"> - <title>Auxiliary Database Objects</title> + <title>Auxiliary database objects</title> <para> - Allows CREATE and DROP of arbitrary database objects, in conjunction with - Hibernate's schema evolution tools, to provide the ability to fully define + Auxiliary database objects allow for the CREATE and DROP of arbitrary database objects. In conjunction with + Hibernate's schema evolution tools, they have the ability to fully define a user schema within the Hibernate mapping files. Although designed specifically - for creating and dropping things like triggers or stored procedures, really any + for creating and dropping things like triggers or stored procedures, any SQL command that can be run via a <literal>java.sql.Statement.execute()</literal> - method is valid here (ALTERs, INSERTS, etc). There are essentially two modes for - defining auxiliary database objects... + method is valid (for example, ALTERs, INSERTS, etc.). There are essentially two modes for + defining auxiliary database objects: </para> <para> - The first mode is to explicitly list the CREATE and DROP commands out in the mapping + The first mode is to explicitly list the CREATE and DROP commands in the mapping file: </para> <programlisting><![CDATA[<hibernate-mapping> @@ -3560,7 +3567,7 @@ </database-object> </hibernate-mapping>]]></programlisting> <para> - The second mode is to supply a custom class which knows how to construct the + The second mode is to supply a custom class that constructs the CREATE and DROP commands. This custom class must implement the <literal>org.hibernate.mapping.AuxiliaryDatabaseObject</literal> interface. </para> @@ -3571,7 +3578,7 @@ </database-object> </hibernate-mapping>]]></programlisting> <para> - Additionally, these database objects can be optionally scoped such that they only + Additionally, these database objects can be optionally scoped so that they only apply when certain dialects are used. </para> <programlisting><![CDATA[<hibernate-mapping> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/batch.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/batch.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/batch.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -29,7 +29,7 @@ <title>Batch processing</title> <para> - A naive approach to inserting 100 000 rows in the database using Hibernate might + A naive approach to inserting 100,000 rows in the database using Hibernate might look like this: </para> @@ -44,26 +44,27 @@ <para> This would fall over with an <literal>OutOfMemoryException</literal> somewhere - around the 50 000th row. That's because Hibernate caches all the newly inserted - <literal>Customer</literal> instances in the session-level cache. + around the 50,000th row. That is because Hibernate caches all the newly inserted + <literal>Customer</literal> instances in the session-level cache. In this chapter + we will show you how to avoid this problem. </para> <para> - In this chapter we'll show you how to avoid this problem. First, however, if you - are doing batch processing, it is absolutely critical that you enable the use of - JDBC batching, if you intend to achieve reasonable performance. Set the JDBC batch - size to a reasonable number (say, 10-50): + + If you are undertaking batch processing you will need to enable the use of + JDBC batching. This is absolutely essential if you want to achieve optimal performance. + Set the JDBC batch size to a reasonable number (10-50, for example): </para> <programlisting><![CDATA[hibernate.jdbc.batch_size 20]]></programlisting> <para id="disablebatching" revision="1"> - Note that Hibernate disables insert batching at the JDBC level transparently if you - use an <literal>identiy</literal> identifier generator. + Hibernate disables insert batching at the JDBC level transparently if you + use an <literal>identity</literal> identifier generator. </para> <para> - You also might like to do this kind of work in a process where interaction with + You can also do this kind of work in a process where interaction with the second-level cache is completely disabled: </para> @@ -78,8 +79,8 @@ <title>Batch inserts</title> <para> - When making new objects persistent, you must <literal>flush()</literal> and - then <literal>clear()</literal> the session regularly, to control the size of + When making new objects persistent <literal>flush()</literal> and + then <literal>clear()</literal> the session regularly in order to control the size of the first-level cache. </para> @@ -105,7 +106,7 @@ <title>Batch updates</title> <para> - For retrieving and updating data the same ideas apply. In addition, you need to + For retrieving and updating data, the same ideas apply. In addition, you need to use <literal>scroll()</literal> to take advantage of server-side cursors for queries that return many rows of data. </para> @@ -135,18 +136,18 @@ <sect1 id="batch-statelesssession"> <title>The StatelessSession interface</title> <para> - Alternatively, Hibernate provides a command-oriented API that may be used for + Alternatively, Hibernate provides a command-oriented API that can be used for streaming data to and from the database in the form of detached objects. A <literal>StatelessSession</literal> has no persistence context associated with it and does not provide many of the higher-level life cycle semantics. In particular, a stateless session does not implement a first-level cache nor interact with any second-level or query cache. It does not implement transactional write-behind or automatic dirty checking. Operations performed - using a stateless session do not ever cascade to associated instances. Collections + using a stateless session never cascade to associated instances. Collections are ignored by a stateless session. Operations performed via a stateless session - bypass Hibernate's event model and interceptors. Stateless sessions are vulnerable - to data aliasing effects, due to the lack of a first-level cache. A stateless - session is a lower-level abstraction, much closer to the underlying JDBC. + bypass Hibernate's event model and interceptors. Due to the lack of a first-level cache, + Stateless sessions are vulnerable to data aliasing effects. A stateless + session is a lower-level abstraction that is much closer to the underlying JDBC. </para> <programlisting><![CDATA[StatelessSession session = sessionFactory.openStatelessSession(); @@ -164,7 +165,7 @@ session.close();]]></programlisting> <para> - Note that in this code example, the <literal>Customer</literal> instances returned + In this code example, the <literal>Customer</literal> instances returned by the query are immediately detached. They are never associated with any persistence context. </para> @@ -172,9 +173,9 @@ <para> The <literal>insert(), update()</literal> and <literal>delete()</literal> operations defined by the <literal>StatelessSession</literal> interface are considered to be - direct database row-level operations, which result in immediate execution of a SQL - <literal>INSERT, UPDATE</literal> or <literal>DELETE</literal> respectively. Thus, - they have very different semantics to the <literal>save(), saveOrUpdate()</literal> + direct database row-level operations. They result in the immediate execution of a SQL + <literal>INSERT, UPDATE</literal> or <literal>DELETE</literal> respectively. + They have different semantics to the <literal>save(), saveOrUpdate()</literal> and <literal>delete()</literal> operations defined by the <literal>Session</literal> interface. </para> @@ -186,18 +187,20 @@ <para> As already discussed, automatic and transparent object/relational mapping is concerned - with the management of object state. This implies that the object state is available - in memory, hence manipulating (using the SQL <literal>Data Manipulation Language</literal> - (DML) statements: <literal>INSERT</literal>, <literal>UPDATE</literal>, <literal>DELETE</literal>) - data directly in the database will not affect in-memory state. However, Hibernate provides methods - for bulk SQL-style DML statement execution which are performed through the + with the management of the object state. The object state is available in memory. This means that manipulating data directly in the database (using the SQL <literal>Data Manipulation Language</literal> + (DML) the statements: <literal>INSERT</literal>, <literal>UPDATE</literal>, <literal>DELETE</literal>) + will not affect in-memory state. However, Hibernate provides methods + for bulk SQL-style DML statement execution that is performed through the Hibernate Query Language (<link linkend="queryhql">HQL</link>). </para> <para> The pseudo-syntax for <literal>UPDATE</literal> and <literal>DELETE</literal> statements - is: <literal>( UPDATE | DELETE ) FROM? EntityName (WHERE where_conditions)?</literal>. Some - points to note: + is: <literal>( UPDATE | DELETE ) FROM? EntityName (WHERE where_conditions)?</literal>. + </para> + + <para> + Some points to note: </para> <itemizedlist spacing="compact"> @@ -208,17 +211,17 @@ </listitem> <listitem> <para> - There can only be a single entity named in the from-clause; it can optionally be + There can only be a single entity named in the from-clause. It can, however, be aliased. If the entity name is aliased, then any property references must - be qualified using that alias; if the entity name is not aliased, then it is + be qualified using that alias. If the entity name is not aliased, then it is illegal for any property references to be qualified. </para> </listitem> <listitem> <para> - No <link linkend="queryhql-joins-forms">joins</link> (either implicit or explicit) - can be specified in a bulk HQL query. Sub-queries may be used in the where-clause; - the subqueries, themselves, may contain joins. + No <link linkend="queryhql-joins-forms">joins</link>, either implicit or explicit, + can be specified in a bulk HQL query. Sub-queries can be used in the where-clause, where + the subqueries themselves may contain joins. </para> </listitem> <listitem> @@ -230,8 +233,8 @@ <para> As an example, to execute an HQL <literal>UPDATE</literal>, use the - <literal>Query.executeUpdate()</literal> method (the method is named for - those familiar with JDBC's <literal>PreparedStatement.executeUpdate()</literal>): + <literal>Query.executeUpdate()</literal> method. The method is named for + those familiar with JDBC's <literal>PreparedStatement.executeUpdate()</literal>: </para> <programlisting><![CDATA[Session session = sessionFactory.openSession(); @@ -247,11 +250,11 @@ session.close();]]></programlisting> <para> - HQL <literal>UPDATE</literal> statements, by default do not effect the + In keeping with the EJB3 specification, HQL <literal>UPDATE</literal> statements, by default, do not effect the <link linkend="mapping-declaration-version">version</link> or the <link linkend="mapping-declaration-timestamp">timestamp</link> property values - for the affected entities; this is in keeping with the EJB3 specification. However, - you can force Hibernate to properly reset the <literal>version</literal> or + for the affected entities. However, + you can force Hibernate to reset the <literal>version</literal> or <literal>timestamp</literal> property values through the use of a <literal>versioned update</literal>. This is achieved by adding the <literal>VERSIONED</literal> keyword after the <literal>UPDATE</literal> keyword. @@ -267,7 +270,7 @@ session.close();]]></programlisting> <para> - Note that custom version types (<literal>org.hibernate.usertype.UserVersionType</literal>) + Custom version types, <literal>org.hibernate.usertype.UserVersionType</literal>, are not allowed in conjunction with a <literal>update versioned</literal> statement. </para> @@ -289,13 +292,13 @@ <para> The <literal>int</literal> value returned by the <literal>Query.executeUpdate()</literal> - method indicate the number of entities effected by the operation. Consider this may or may not + method indicates the number of entities effected by the operation. This may or may not correlate to the number of rows effected in the database. An HQL bulk operation might result in - multiple actual SQL statements being executed, for joined-subclass, for example. The returned + multiple actual SQL statements being executed (for joined-subclass, for example). The returned number indicates the number of actual entities affected by the statement. Going back to the example of joined-subclass, a delete against one of the subclasses may actually result in deletes against not just the table to which that subclass is mapped, but also the "root" - table and potentially joined-subclass tables further down the inheritence hierarchy. + table and potentially joined-subclass tables further down the inheritance hierarchy. </para> <para> @@ -310,10 +313,10 @@ Only the INSERT INTO ... SELECT ... form is supported; not the INSERT INTO ... VALUES ... form. </para> <para> - The properties_list is analogous to the <literal>column speficiation</literal> + The properties_list is analogous to the <literal>column specification</literal> in the SQL <literal>INSERT</literal> statement. For entities involved in mapped - inheritence, only properties directly defined on that given class-level can be - used in the properties_list. Superclass properties are not allowed; and subclass + inheritance, only properties directly defined on that given class-level can be + used in the properties_list. Superclass properties are not allowed and subclass properties do not make sense. In other words, <literal>INSERT</literal> statements are inherently non-polymorphic. </para> @@ -322,8 +325,8 @@ <para> select_statement can be any valid HQL select query, with the caveat that the return types must match the types expected by the insert. Currently, this is checked during query - compilation rather than allowing the check to relegate to the database. Note however - that this might cause problems between Hibernate <literal>Type</literal>s which are + compilation rather than allowing the check to relegate to the database. + This might, however, cause problems between Hibernate <literal>Type</literal>s which are <emphasis>equivalent</emphasis> as opposed to <emphasis>equal</emphasis>. This might cause issues with mismatches between a property defined as a <literal>org.hibernate.type.DateType</literal> and a property defined as a <literal>org.hibernate.type.TimestampType</literal>, even though the @@ -333,14 +336,14 @@ <listitem> <para> For the id property, the insert statement gives you two options. You can either - explicitly specify the id property in the properties_list (in which case its value - is taken from the corresponding select expression) or omit it from the properties_list - (in which case a generated value is used). This later option is only available when + explicitly specify the id property in the properties_list, in which case its value + is taken from the corresponding select expression, or omit it from the properties_list, + in which case a generated value is used. This latter option is only available when using id generators that operate in the database; attempting to use this option with - any "in memory" type generators will cause an exception during parsing. Note that - for the purposes of this discussion, in-database generators are considered to be + any "in memory" type generators will cause an exception during parsing. + For the purposes of this discussion, in-database generators are considered to be <literal>org.hibernate.id.SequenceGenerator</literal> (and its subclasses) and - any implementors of <literal>org.hibernate.id.PostInsertIdentifierGenerator</literal>. + any implementers of <literal>org.hibernate.id.PostInsertIdentifierGenerator</literal>. The most notable exception here is <literal>org.hibernate.id.TableHiLoGenerator</literal>, which cannot be used because it does not expose a selectable way to get its values. </para> @@ -349,15 +352,15 @@ <para> For properties mapped as either <literal>version</literal> or <literal>timestamp</literal>, the insert statement gives you two options. You can either specify the property in the - properties_list (in which case its value is taken from the corresponding select expressions) - or omit it from the properties_list (in which case the <literal>seed value</literal> defined - by the <literal>org.hibernate.type.VersionType</literal> is used). + properties_list, in which case its value is taken from the corresponding select expressions, + or omit it from the properties_list, in which case the <literal>seed value</literal> defined + by the <literal>org.hibernate.type.VersionType</literal> is used. </para> </listitem> </itemizedlist> <para> - An example HQL <literal>INSERT</literal> statement execution: + The following is an example of an HQL <literal>INSERT</literal> statement execution: </para> <programlisting><![CDATA[Session session = sessionFactory.openSession(); Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/best_practices.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/best_practices.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/best_practices.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -30,7 +30,7 @@ <variablelist spacing="compact"> <varlistentry> - <term>Write fine-grained classes and map them using <literal>&lt;component&gt;</literal>.</term> + <term>Write fine-grained classes and map them using <literal>&lt;component&gt;</literal>:</term> <listitem> <para> Use an <literal>Address</literal> class to encapsulate <literal>street</literal>, @@ -40,17 +40,17 @@ </listitem> </varlistentry> <varlistentry> - <term>Declare identifier properties on persistent classes.</term> + <term>Declare identifier properties on persistent classes:</term> <listitem> <para> - Hibernate makes identifier properties optional. There are all sorts of reasons why - you should use them. We recommend that identifiers be 'synthetic' (generated, with - no business meaning). + Hibernate makes identifier properties optional. There are a range of reasons why + you should use them. We recommend that identifiers be 'synthetic', that is, generated with + no business meaning. </para> </listitem> </varlistentry> <varlistentry> - <term>Identify natural keys.</term> + <term>Identify natural keys:</term> <listitem> <para> Identify natural keys for all entities, and map them using @@ -60,17 +60,17 @@ </listitem> </varlistentry> <varlistentry> - <term>Place each class mapping in its own file.</term> + <term>Place each class mapping in its own file:</term> <listitem> <para> - Don't use a single monolithic mapping document. Map <literal>com.eg.Foo</literal> in - the file <literal>com/eg/Foo.hbm.xml</literal>. This makes particularly good sense in + Do not use a single monolithic mapping document. Map <literal>com.eg.Foo</literal> in + the file <literal>com/eg/Foo.hbm.xml</literal>. This makes sense, particularly in a team environment. </para> </listitem> </varlistentry> <varlistentry> - <term>Load mappings as resources.</term> + <term>Load mappings as resources:</term> <listitem> <para> Deploy the mappings along with the classes they map. @@ -78,11 +78,11 @@ </listitem> </varlistentry> <varlistentry> - <term>Consider externalising query strings.</term> + <term>Consider externalizing query strings:</term> <listitem> <para> - This is a good practice if your queries call non-ANSI-standard SQL functions. - Externalising the query strings to mapping files will make the application more + This is recommended if your queries call non-ANSI-standard SQL functions. + Externalizing the query strings to mapping files will make the application more portable. </para> </listitem> @@ -91,103 +91,103 @@ <term>Use bind variables.</term> <listitem> <para> - As in JDBC, always replace non-constant values by "?". Never use string manipulation to - bind a non-constant value in a query! Even better, consider using named parameters in + As in JDBC, always replace non-constant values by "?". Do not use string manipulation to + bind a non-constant value in a query. You should also consider using named parameters in queries. </para> </listitem> </varlistentry> <varlistentry> - <term>Don't manage your own JDBC connections.</term> + <term>Do not manage your own JDBC connections:</term> <listitem> <para> - Hibernate lets the application manage JDBC connections. This approach should be considered - a last-resort. If you can't use the built-in connections providers, consider providing your + Hibernate allows the application to manage JDBC connections, but his approach should be considered + a last-resort. If you cannot use the built-in connection providers, consider providing your own implementation of <literal>org.hibernate.connection.ConnectionProvider</literal>. </para> </listitem> </varlistentry> <varlistentry> - <term>Consider using a custom type.</term> + <term>Consider using a custom type:</term> <listitem> <para> - Suppose you have a Java type, say from some library, that needs to be persisted but doesn't + Suppose you have a Java type from a library that needs to be persisted but does not provide the accessors needed to map it as a component. You should consider implementing <literal>org.hibernate.UserType</literal>. This approach frees the application - code from implementing transformations to / from a Hibernate type. + code from implementing transformations to/from a Hibernate type. </para> </listitem> </varlistentry> <varlistentry> - <term>Use hand-coded JDBC in bottlenecks.</term> + <term>Use hand-coded JDBC in bottlenecks:</term> <listitem> <para> In performance-critical areas of the system, some kinds of operations might benefit from - direct JDBC. But please, wait until you <emphasis>know</emphasis> something is a bottleneck. - And don't assume that direct JDBC is necessarily faster. If you need to use direct JDBC, it might - be worth opening a Hibernate <literal>Session</literal> and using that JDBC connection. That + direct JDBC. Do not assume, however, that JDBC is necessarily faster. Please wait until you <emphasis>know</emphasis> something is a bottleneck. + If you need to use direct JDBC, + you can open a Hibernate <literal>Session</literal> and usingfile:///usr/share/doc/HTML/en-US/index.html that JDBC connection. This way you can still use the same transaction strategy and underlying connection provider. </para> </listitem> </varlistentry> <varlistentry> - <term>Understand <literal>Session</literal> flushing.</term> + <term>Understand <literal>Session</literal> flushing:</term> <listitem> <para> - From time to time the Session synchronizes its persistent state with the database. Performance will - be affected if this process occurs too often. You may sometimes minimize unnecessary flushing by - disabling automatic flushing or even by changing the order of queries and other operations within a + Sometimes the Session synchronizes its persistent state with the database. Performance will + be affected if this process occurs too often. You can sometimes minimize unnecessary flushing by + disabling automatic flushing, or even by changing the order of queries and other operations within a particular transaction. </para> </listitem> </varlistentry> <varlistentry> - <term>In a three tiered architecture, consider using detached objects.</term> + <term>In a three tiered architecture, consider using detached objects:</term> <listitem> <para> - When using a servlet / session bean architecture, you could pass persistent objects loaded in - the session bean to and from the servlet / JSP layer. Use a new session to service each request. + When using a servlet/session bean architecture, you can pass persistent objects loaded in + the session bean to and from the servlet/JSP layer. Use a new session to service each request. Use <literal>Session.merge()</literal> or <literal>Session.saveOrUpdate()</literal> to synchronize objects with the database. </para> </listitem> </varlistentry> <varlistentry> - <term>In a two tiered architecture, consider using long persistence contexts.</term> + <term>In a two tiered architecture, consider using long persistence contexts:</term> <listitem> <para> Database Transactions have to be as short as possible for best scalability. However, it is often - neccessary to implement long running <emphasis>application transactions</emphasis>, a single + necessary to implement long running <emphasis>application transactions</emphasis>, a single unit-of-work from the point of view of a user. An application transaction might span several client request/response cycles. It is common to use detached objects to implement application - transactions. An alternative, extremely appropriate in two tiered architecture, is to maintain - a single open persistence contact (session) for the whole life cycle of the application transaction - and simply disconnect from the JDBC connection at the end of each request and reconnect at the + transactions. An appropriate alternative in a two tiered architecture, is to maintain + a single open persistence contact session for the whole life cycle of the application transaction. Then + simply disconnect from the JDBC connection at the end of each request and reconnect at the beginning of the subsequent request. Never share a single session across more than one application - transaction, or you will be working with stale data. + transaction or you will be working with stale data. </para> </listitem> </varlistentry> <varlistentry> - <term>Don't treat exceptions as recoverable.</term> + <term>Do not treat exceptions as recoverable:</term> <listitem> <para> This is more of a necessary practice than a "best" practice. When an exception occurs, roll back - the <literal>Transaction</literal> and close the <literal>Session</literal>. If you don't, Hibernate - can't guarantee that in-memory state accurately represents persistent state. As a special case of this, + the <literal>Transaction</literal> and close the <literal>Session</literal>. If you do not do this, Hibernate + cannot guarantee that in-memory state accurately represents the persistent state. For example, do not use <literal>Session.load()</literal> to determine if an instance with the given identifier exists on the database; use <literal>Session.get()</literal> or a query instead. </para> </listitem> </varlistentry> <varlistentry> - <term>Prefer lazy fetching for associations.</term> + <term>Prefer lazy fetching for associations:</term> <listitem> <para> Use eager fetching sparingly. Use proxies and lazy collections for most associations to classes that are not likely to be completely held in the second-level cache. For associations to cached classes, where there is an a extremely high probability of a cache hit, explicitly disable eager fetching using - <literal>lazy="false"</literal>. When an join fetching is appropriate to a particular use + <literal>lazy="false"</literal>. When join fetching is appropriate to a particular use case, use a query with a <literal>left join fetch</literal>. </para> </listitem> @@ -195,7 +195,7 @@ <varlistentry> <term> Use the <emphasis>open session in view</emphasis> pattern, or a disciplined - <emphasis>assembly phase</emphasis> to avoid problems with unfetched data. + <emphasis>assembly phase</emphasis> to avoid problems with unfetched data: </term> <listitem> <para> @@ -203,40 +203,40 @@ In a traditional EJB architecture, DTOs serve dual purposes: first, they work around the problem that entity beans are not serializable; second, they implicitly define an assembly phase where all data to be used by the view is fetched and marshalled into the DTOs before returning control - to the presentation tier. Hibernate eliminates the first purpose. However, you will still need - an assembly phase (think of your business methods as having a strict contract with the presentation - tier about what data is available in the detached objects) unless you are prepared to hold the - persistence context (the session) open across the view rendering process. This is not a limitation - of Hibernate! It is a fundamental requirement of safe transactional data access. + to the presentation tier. Hibernate eliminates the first purpose. Unless you are prepared to hold the + persistence context (the session) open across the view rendering process, you will still need + an assembly phase. Think of your business methods as having a strict contract with the presentation + tier about what data is available in the detached objects. This is not a limitation + of Hibernate. It is a fundamental requirement of safe transactional data access. </para> </listitem> </varlistentry> <varlistentry> - <term>Consider abstracting your business logic from Hibernate.</term> + <term>Consider abstracting your business logic from Hibernate:</term> <listitem> <para> - Hide (Hibernate) data-access code behind an interface. Combine the <emphasis>DAO</emphasis> and + Hide Hibernate data-access code behind an interface. Combine the <emphasis>DAO</emphasis> and <emphasis>Thread Local Session</emphasis> patterns. You can even have some classes persisted by - handcoded JDBC, associated to Hibernate via a <literal>UserType</literal>. (This advice is - intended for "sufficiently large" applications; it is not appropriate for an application with - five tables!) + handcoded JDBC associated to Hibernate via a <literal>UserType</literal>. This advice is, however, + intended for "sufficiently large" applications. It is not appropriate for an application with + five tables. </para> </listitem> </varlistentry> <varlistentry> - <term>Don't use exotic association mappings.</term> + <term>Do not use exotic association mappings:</term> <listitem> <para> - Good usecases for a real many-to-many associations are rare. Most of the time you need + Practical test cases for real many-to-many associations are rare. Most of the time you need additional information stored in the "link table". In this case, it is much better to - use two one-to-many associations to an intermediate link class. In fact, we think that - most associations are one-to-many and many-to-one, you should be careful when using any - other association style and ask yourself if it is really neccessary. + use two one-to-many associations to an intermediate link class. In fact, + most associations are one-to-many and many-to-one. For this reason, you should proceed cautiously when using any + other association style. </para> </listitem> </varlistentry> <varlistentry> - <term>Prefer bidirectional associations.</term> + <term>Prefer bidirectional associations:</term> <listitem> <para> Unidirectional associations are more difficult to query. In a large application, almost Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/collection_mapping.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/collection_mapping.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/collection_mapping.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -26,14 +26,14 @@ <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> <chapter id="collections"> - <title>Collection Mapping</title> + <title>Collection mapping</title> <sect1 id="collections-persistent" revision="3"> <title>Persistent collections</title> <para> Hibernate requires that persistent collection-valued fields be declared - as an interface type, for example: + as an interface type. For example: </para> <programlisting><![CDATA[public class Product { @@ -50,19 +50,19 @@ The actual interface might be <literal>java.util.Set</literal>, <literal>java.util.Collection</literal>, <literal>java.util.List</literal>, <literal>java.util.Map</literal>, <literal>java.util.SortedSet</literal>, - <literal>java.util.SortedMap</literal> or ... anything you like! (Where - "anything you like" means you will have to write an implementation of + <literal>java.util.SortedMap</literal> or anything you like + ("anything you like" means you will have to write an implementation of <literal>org.hibernate.usertype.UserCollectionType</literal>.) </para> <para> - Notice how we initialized the instance variable with an instance of + Notice how the instance variable was initialized with an instance of <literal>HashSet</literal>. This is the best way to initialize collection valued properties of newly instantiated (non-persistent) instances. When - you make the instance persistent - by calling <literal>persist()</literal>, - for example - Hibernate will actually replace the <literal>HashSet</literal> + you make the instance persistent, by calling <literal>persist()</literal> + for example, Hibernate will actually replace the <literal>HashSet</literal> with an instance of Hibernate's own implementation of <literal>Set</literal>. - Watch out for errors like this: + Be aware of the following errors: </para> <programlisting><![CDATA[Cat cat = new DomesticCat(); @@ -79,24 +79,24 @@ The persistent collections injected by Hibernate behave like <literal>HashMap</literal>, <literal>HashSet</literal>, <literal>TreeMap</literal>, <literal>TreeSet</literal> or - <literal>ArrayList</literal>, depending upon the interface type. + <literal>ArrayList</literal>, depending on the interface type. </para> <para> Collections instances have the usual behavior of value types. They are automatically persisted when referenced by a persistent object and - automatically deleted when unreferenced. If a collection is passed from one + are automatically deleted when unreferenced. If a collection is passed from one persistent object to another, its elements might be moved from one table to - another. Two entities may not share a reference to the same collection + another. Two entities cannot share a reference to the same collection instance. Due to the underlying relational model, collection-valued properties - do not support null value semantics; Hibernate does not distinguish between + do not support null value semantics. Hibernate does not distinguish between a null collection reference and an empty collection. </para> <para> - You shouldn't have to worry much about any of this. Use persistent collections - the same way you use ordinary Java collections. Just make sure you understand - the semantics of bidirectional associations (discussed later). + Use persistent collections + the same way you use ordinary Java collections. However, please ensure you understand + the semantics of bidirectional associations (these are discussed later). </para> </sect1> @@ -106,15 +106,15 @@ <tip> <para> - There are quite a range of mappings that can be generated for collections, covering + There are quite a range of mappings that can be generated for collections that cover many common relational models. We suggest you experiment with the schema generation tool - to get a feeling for how various mapping declarations translate to database tables. + so that you understand how various mapping declarations translate to database tables. </para> </tip> <para> The Hibernate mapping element used for mapping a collection depends upon - the type of the interface. For example, a <literal>&lt;set&gt;</literal> + the type of interface. For example, a <literal>&lt;set&gt;</literal> element is used for mapping properties of type <literal>Set</literal>. </para> @@ -177,94 +177,94 @@ <calloutlist> <callout arearefs="mappingcollection1"> <para> - <literal>name</literal> the collection property name + <literal>name</literal>: the collection property name </para> </callout> <callout arearefs="mappingcollection2"> <para> - <literal>table</literal> (optional - defaults to property name) the - name of the collection table (not used for one-to-many associations) + <literal>table</literal> (optional - defaults to property name): the + name of the collection table. It is not used for one-to-many associations. </para> </callout> <callout arearefs="mappingcollection3"> <para> - <literal>schema</literal> (optional) the name of a table schema to + <literal>schema</literal> (optional): the name of a table schema to override the schema declared on the root element </para> </callout> <callout arearefs="mappingcollection4"> <para> - <literal>lazy</literal> (optional - defaults to <literal>true</literal>) - may be used to disable lazy fetching and specify that the association is - always eagerly fetched, or to enable "extra-lazy" fetching where most - operations do not initialize the collection (suitable for very large - collections) + <literal>lazy</literal> (optional - defaults to <literal>true</literal>): + disables lazy fetching and specifies that the association is + always eagerly fetched. It can also be used to enable "extra-lazy" fetching where most + operations do not initialize the collection. This is suitable for large + collections. </para> </callout> <callout arearefs="mappingcollection5"> <para> - <literal>inverse</literal> (optional - defaults to <literal>false</literal>) - mark this collection as the "inverse" end of a bidirectional association + <literal>inverse</literal> (optional - defaults to <literal>false</literal>): + marks this collection as the "inverse" end of a bidirectional association. </para> </callout> <callout arearefs="mappingcollection6"> <para> - <literal>cascade</literal> (optional - defaults to <literal>none</literal>) - enable operations to cascade to child entities + <literal>cascade</literal> (optional - defaults to <literal>none</literal>): + enables operations to cascade to child entities. </para> </callout> <callout arearefs="mappingcollection7"> <para> - <literal>sort</literal> (optional) specify a sorted collection with - <literal>natural</literal> sort order, or a given comparator class + <literal>sort</literal> (optional): specifies a sorted collection with + <literal>natural</literal> sort order or a given comparator class. </para> </callout> <callout arearefs="mappingcollection8"> <para> - <literal>order-by</literal> (optional, JDK1.4 only) specify a table column (or columns) + <literal>order-by</literal> (optional, JDK1.4 only): specifies a table column or columns that define the iteration order of the <literal>Map</literal>, <literal>Set</literal> - or bag, together with an optional <literal>asc</literal> or <literal>desc</literal> + or bag, together with an optional <literal>asc</literal> or <literal>desc</literal>. </para> </callout> <callout arearefs="mappingcollection9"> <para> - <literal>where</literal> (optional) specify an arbitrary SQL <literal>WHERE</literal> - condition to be used when retrieving or removing the collection (useful if the - collection should contain only a subset of the available data) + <literal>where</literal> (optional): specifies an arbitrary SQL <literal>WHERE</literal> + condition that is used when retrieving or removing the collection. This is useful if the + collection needs to contain only a subset of the available data. </para> </callout> <callout arearefs="mappingcollection10"> <para> - <literal>fetch</literal> (optional, defaults to <literal>select</literal>) Choose + <literal>fetch</literal> (optional, defaults to <literal>select</literal>): chooses between outer-join fetching, fetching by sequential select, and fetching by sequential subselect. </para> </callout> <callout arearefs="mappingcollection11"> <para> - <literal>batch-size</literal> (optional, defaults to <literal>1</literal>) specify a + <literal>batch-size</literal> (optional, defaults to <literal>1</literal>): specifies a "batch size" for lazily fetching instances of this collection. </para> </callout> <callout arearefs="mappingcollection12"> <para> - <literal>access</literal> (optional - defaults to <literal>property</literal>): The - strategy Hibernate should use for accessing the collection property value. + <literal>access</literal> (optional - defaults to <literal>property</literal>): the + strategy Hibernate uses for accessing the collection property value. </para> </callout> <callout arearefs="mappingcollection13"> <para> <literal>optimistic-lock</literal> (optional - defaults to <literal>true</literal>): - Species that changes to the state of the collection results in increment of the - owning entity's version. (For one to many associations, it is often reasonable to - disable this setting.) + specifies that changes to the state of the collection results in increments of the + owning entity's version. For one-to-many associations you may want to + disable this setting. </para> </callout> <callout arearefs="mappingcollection14"> <para> <literal>mutable</literal> (optional - defaults to <literal>true</literal>): - A value of <literal>false</literal> specifies that the elements of the - collection never change (a minor performance optimization in some cases). + a value of <literal>false</literal> specifies that the elements of the + collection never change. This allows for minor performance optimization in some cases. </para> </callout> </calloutlist> @@ -276,22 +276,22 @@ <para> Collection instances are distinguished in the database by the foreign key of the entity that owns the collection. This foreign key is referred to as the - <emphasis>collection key column</emphasis> (or columns) of the collection + <emphasis>collection key column</emphasis>, or columns, of the collection table. The collection key column is mapped by the <literal>&lt;key&gt;</literal> element. </para> <para> - There may be a nullability constraint on the foreign key column. For most - collections, this is implied. For unidirectional one to many associations, - the foreign key column is nullable by default, so you might need to specify + There can be a nullability constraint on the foreign key column. For most + collections, this is implied. For unidirectional one-to-many associations, + the foreign key column is nullable by default, so you may need to specify <literal>not-null="true"</literal>. </para> <programlisting><![CDATA[<key column="productSerialNumber" not-null="true"/>]]></programlisting> <para> - The foreign key constraint may use <literal>ON DELETE CASCADE</literal>. + The foreign key constraint can use <literal>ON DELETE CASCADE</literal>. </para> <programlisting><![CDATA[<key column="productSerialNumber" on-delete="cascade"/>]]></programlisting> @@ -307,12 +307,12 @@ <title>Collection elements</title> <para> - Collections may contain almost any other Hibernate type, including all basic types, - custom types, components, and of course, references to other entities. This is an - important distinction: an object in a collection might be handled with "value" - semantics (its life cycle fully depends on the collection owner) or it might be a - reference to another entity, with its own life cycle. In the latter case, only the - "link" between the two objects is considered to be state held by the collection. + Collections can contain almost any other Hibernate type, including: basic types, + custom types, components and references to other entities. This is an + important distinction. An object in a collection might be handled with "value" + semantics (its life cycle fully depends on the collection owner), or it might be a + reference to another entity with its own life cycle. In the latter case, only the + "link" between the two objects is considered to be a state held by the collection. </para> <para> @@ -331,15 +331,15 @@ <para> All collection mappings, except those with set and bag semantics, need an - <emphasis>index column</emphasis> in the collection table - a column that maps to an + <emphasis>index column</emphasis> in the collection table. An index column is a column that maps to an array index, or <literal>List</literal> index, or <literal>Map</literal> key. The index of a <literal>Map</literal> may be of any basic type, mapped with - <literal>&lt;map-key&gt;</literal>, it may be an entity reference mapped with - <literal>&lt;map-key-many-to-many&gt;</literal>, or it may be a composite type, + <literal>&lt;map-key&gt;</literal>. It can be an entity reference mapped with + <literal>&lt;map-key-many-to-many&gt;</literal>, or it can be a composite type mapped with <literal>&lt;composite-map-key&gt;</literal>. The index of an array or list is always of type <literal>integer</literal> and is mapped using the <literal>&lt;list-index&gt;</literal> element. The mapped column contains - sequential integers (numbered from zero, by default). + sequential integers that are numbered from zero by default. </para> <programlistingco> @@ -353,13 +353,13 @@ <calloutlist> <callout arearefs="index1"> <para> - <literal>column_name</literal> (required): The name of the column holding the + <literal>column_name</literal> (required): the name of the column holding the collection index values. </para> </callout> <callout arearefs="index1"> <para> - <literal>base</literal> (optional, defaults to <literal>0</literal>): The value + <literal>base</literal> (optional - defaults to <literal>0</literal>): the value of the index column that corresponds to the first element of the list or array. </para> </callout> @@ -381,19 +381,19 @@ <calloutlist> <callout arearefs="mapkey1"> <para> - <literal>column</literal> (optional): The name of the column holding the + <literal>column</literal> (optional): the name of the column holding the collection index values. </para> </callout> <callout arearefs="mapkey2"> <para> - <literal>formula</literal> (optional): A SQL formula used to evaluate the + <literal>formula</literal> (optional): a SQL formula used to evaluate the key of the map. </para> </callout> <callout arearefs="mapkey3"> <para> - <literal>type</literal> (reguired): The type of the map keys. + <literal>type</literal> (required): the type of the map keys. </para> </callout> </calloutlist> @@ -413,19 +413,19 @@ <calloutlist> <callout arearefs="indexmanytomany1"> <para> - <literal>column</literal> (optional): The name of the foreign key + <literal>column</literal> (optional): the name of the foreign key column for the collection index values. </para> </callout> <callout arearefs="indexmanytomany2"> <para> - <literal>formula</literal> (optional): A SQL formula used to evaluate the + <literal>formula</literal> (optional): a SQ formula used to evaluate the foreign key of the map key. </para> </callout> <callout arearefs="indexmanytomany3"> <para> - <literal>class</literal> (required): The entity class used as the map key. + <literal>class</literal> (required): the entity class used as the map key. </para> </callout> </calloutlist> @@ -433,9 +433,9 @@ <para> - If your table doesn't have an index column, and you still wish to use <literal>List</literal> - as the property type, you should map the property as a Hibernate <emphasis>&lt;bag&gt;</emphasis>. - A bag does not retain its order when it is retrieved from the database, but it may be + If your table does not have an index column, and you still wish to use <literal>List</literal> + as the property type, you can map the property as a Hibernate <emphasis>&lt;bag&gt;</emphasis>. + A bag does not retain its order when it is retrieved from the database, but it can be optionally sorted or ordered. </para> @@ -445,14 +445,14 @@ <title>Collections of values and many-to-many associations</title> <para> - Any collection of values or many-to-many association requires a dedicated + Any collection of values or many-to-many associations requires a dedicated <emphasis>collection table</emphasis> with a foreign key column or columns, - <emphasis>collection element column</emphasis> or columns and possibly + <emphasis>collection element column</emphasis> or columns, and possibly an index column or columns. </para> <para> - For a collection of values, we use the <literal>&lt;element&gt;</literal> tag. + For a collection of values use the <literal>&lt;element&gt;</literal> tag. For example: </para> <programlistingco> @@ -475,19 +475,19 @@ <calloutlist> <callout arearefs="element1b"> <para> - <literal>column</literal> (optional): The name of the column holding the + <literal>column</literal> (optional): the name of the column holding the collection element values. </para> </callout> <callout arearefs="element2b"> <para> - <literal>formula</literal> (optional): An SQL formula used to evaluate the + <literal>formula</literal> (optional): an SQL formula used to evaluate the element. </para> </callout> <callout arearefs="element3b"> <para> - <literal>type</literal> (required): The type of the collection element. + <literal>type</literal> (required): the type of the collection element. </para> </callout> </calloutlist> @@ -524,54 +524,54 @@ <calloutlist> <callout arearefs="manytomany1"> <para> - <literal>column</literal> (optional): The name of the element foreign key column. + <literal>column</literal> (optional): the name of the element foreign key column. </para> </callout> <callout arearefs="manytomany2"> <para> - <literal>formula</literal> (optional): An SQL formula used to evaluate the element + <literal>formula</literal> (optional): an SQL formula used to evaluate the element foreign key value. </para> </callout> <callout arearefs="manytomany3"> <para> - <literal>class</literal> (required): The name of the associated class. + <literal>class</literal> (required): the name of the associated class. </para> </callout> <callout arearefs="manytomany4"> <para> <literal>fetch</literal> (optional - defaults to <literal>join</literal>): enables outer-join or sequential select fetching for this association. This - is a special case; for full eager fetching (in a single <literal>SELECT</literal>) + is a special case; for full eager fetching in a single <literal>SELECT</literal> of an entity and its many-to-many relationships to other entities, you would - enable <literal>join</literal> fetching not only of the collection itself, + enable <literal>join</literal> fetching,not only of the collection itself, but also with this attribute on the <literal>&lt;many-to-many&gt;</literal> nested element. </para> </callout> <callout arearefs="manytomany5"> <para> - <literal>unique</literal> (optional): Enable the DDL generation of a unique + <literal>unique</literal> (optional): enables the DDL generation of a unique constraint for the foreign-key column. This makes the association multiplicity - effectively one to many. + effectively one-to-many. </para> </callout> <callout arearefs="manytomany6"> <para> <literal>not-found</literal> (optional - defaults to <literal>exception</literal>): - Specifies how foreign keys that reference missing rows will be handled: + specifies how foreign keys that reference missing rows will be handled: <literal>ignore</literal> will treat a missing row as a null association. </para> </callout> <callout arearefs="manytomany7"> <para> - <literal>entity-name</literal> (optional): The entity name of the associated class, + <literal>entity-name</literal> (optional): the entity name of the associated class, as an alternative to <literal>class</literal>. </para> </callout> <callout arearefs="manytomany8"> <para> - <literal>property-ref</literal>: (optional) The name of a property of the associated + <literal>property-ref</literal> (optional): the name of a property of the associated class that is joined to this foreign key. If not specified, the primary key of the associated class is used. </para> @@ -579,8 +579,11 @@ </calloutlist> </programlistingco> + <para> + Here are some examples. + </para> <para> - Some examples, first, a set of strings: + A set of strings: </para> <programlisting><![CDATA[<set name="names" table="person_names"> @@ -589,8 +592,8 @@ </set>]]></programlisting> <para> - A bag containing integers (with an iteration order determined by the - <literal>order-by</literal> attribute): + A bag containing integers with an iteration order determined by the + <literal>order-by</literal> attribute: </para> <programlisting><![CDATA[<bag name="sizes" @@ -601,7 +604,7 @@ </bag>]]></programlisting> <para> - An array of entities - in this case, a many to many association: + An array of entities, in this case, a many-to-many association: </para> <programlisting><![CDATA[<array name="addresses" @@ -626,7 +629,7 @@ </map>]]></programlisting> <para> - A list of components (discussed in the next chapter): + A list of components (this is discussed in the next chapter): </para> <programlisting><![CDATA[<list name="carComponents" @@ -646,30 +649,30 @@ <title>One-to-many associations</title> <para> - A <emphasis>one to many association</emphasis> links the tables of two classes - via a foreign key, with no intervening collection table. This mapping loses + A <emphasis>one-to-many association</emphasis> links the tables of two classes + via a foreign key with no intervening collection table. This mapping loses certain semantics of normal Java collections: </para> <itemizedlist spacing="compact"> <listitem> <para> - An instance of the contained entity class may not belong to more than - one instance of the collection + An instance of the contained entity class cannot belong to more than + one instance of the collection. </para> </listitem> <listitem> <para> - An instance of the contained entity class may not appear at more than - one value of the collection index + An instance of the contained entity class cannot appear at more than + one value of the collection index. </para> </listitem> </itemizedlist> <para> An association from <literal>Product</literal> to <literal>Part</literal> requires - existence of a foreign key column and possibly an index column to the <literal>Part</literal> - table. A <literal>&lt;one-to-many&gt;</literal> tag indicates that this is a one to many + the existence of a foreign key column and possibly an index column to the <literal>Part</literal> + table. A <literal>&lt;one-to-many&gt;</literal> tag indicates that this is a one-to-many association. </para> @@ -689,19 +692,19 @@ <calloutlist> <callout arearefs="onetomany1"> <para> - <literal>class</literal> (required): The name of the associated class. + <literal>class</literal> (required): the name of the associated class. </para> </callout> <callout arearefs="onetomany2"> <para> <literal>not-found</literal> (optional - defaults to <literal>exception</literal>): - Specifies how cached identifiers that reference missing rows will be handled: + specifies how cached identifiers that reference missing rows will be handled. <literal>ignore</literal> will treat a missing row as a null association. </para> </callout> <callout arearefs="onetomany3"> <para> - <literal>entity-name</literal> (optional): The entity name of the associated class, + <literal>entity-name</literal> (optional): the entity name of the associated class, as an alternative to <literal>class</literal>. </para> </callout> @@ -709,24 +712,26 @@ </programlistingco> <para> - Notice that the <literal>&lt;one-to-many&gt;</literal> element does not need to + The <literal>&lt;one-to-many&gt;</literal> element does not need to declare any columns. Nor is it necessary to specify the <literal>table</literal> name anywhere. </para> - <para> - <emphasis>Very important note:</emphasis> If the foreign key column of a + <warning> + <para> + If the foreign key column of a <literal>&lt;one-to-many&gt;</literal> association is declared <literal>NOT NULL</literal>, you must declare the <literal>&lt;key&gt;</literal> mapping <literal>not-null="true"</literal> or <emphasis>use a bidirectional association</emphasis> with the collection mapping marked <literal>inverse="true"</literal>. See the discussion - of bidirectional associations later in this chapter. + of bidirectional associations later in this chapter for more information. </para> - + </warning> + <para> - This example shows a map of <literal>Part</literal> entities by name (where - <literal>partName</literal> is a persistent property of <literal>Part</literal>). - Notice the use of a formula-based index. + The following example shows a map of <literal>Part</literal> entities by name, where + <literal>partName</literal> is a persistent property of <literal>Part</literal>. + Notice the use of a formula-based index: </para> <programlisting><![CDATA[<map name="parts" @@ -775,12 +780,12 @@ </para> <para> - If you want the database itself to order the collection elements use the + If you want the database itself to order the collection elements, use the <literal>order-by</literal> attribute of <literal>set</literal>, <literal>bag</literal> or <literal>map</literal> mappings. This solution is only available under - JDK 1.4 or higher (it is implemented using <literal>LinkedHashSet</literal> or - <literal>LinkedHashMap</literal>). This performs the ordering in the SQL query, - not in memory. + JDK 1.4 or higher and is implemented using <literal>LinkedHashSet</literal> or + <literal>LinkedHashMap</literal>. This performs the ordering in the SQL query and + not in the memory. </para> <programlisting><![CDATA[<set name="aliases" table="person_aliases" order-by="lower(name) asc"> @@ -794,14 +799,17 @@ <element column="hol_date type="date"/> </map>]]></programlisting> - <para> - Note that the value of the <literal>order-by</literal> attribute is an SQL ordering, not - a HQL ordering! + <note> + <title>Note</title> + <para> + The value of the <literal>order-by</literal> attribute is an SQL ordering, not + an HQL ordering. </para> + </note> <para> - Associations may even be sorted by some arbitrary criteria at runtime using a collection - <literal>filter()</literal>. + Associations can even be sorted by arbitrary criteria at runtime using a collection + <literal>filter()</literal>: </para> <programlisting><![CDATA[sortedUsers = s.createFilter( group.getUsers(), "order by this.name" ).list();]]></programlisting> @@ -821,7 +829,7 @@ <term>one-to-many</term> <listitem> <para> - set or bag valued at one end, single-valued at the other + set or bag valued at one end and single-valued at the other </para> </listitem> </varlistentry> @@ -838,14 +846,14 @@ </para> <para> - You may specify a bidirectional many-to-many association simply by mapping two + You can specify a bidirectional many-to-many association by mapping two many-to-many associations to the same database table and declaring one end as - <emphasis>inverse</emphasis> (which one is your choice, but it can not be an - indexed collection). + <emphasis>inverse</emphasis>. You cannot select an + indexed collection. </para> <para> - Here's an example of a bidirectional many-to-many association; each category can + Here is an example of a bidirectional many-to-many association that illustrates how each category can have many items and each item can be in many categories: </para> @@ -872,9 +880,9 @@ <para> Changes made only to the inverse end of the association are <emphasis>not</emphasis> persisted. This means that Hibernate has two representations in memory for every - bidirectional association, one link from A to B and another link from B to A. This - is easier to understand if you think about the Java object model and how we create - a many-to-many relationship in Java: + bidirectional association: one link from A to B and another link from B to A. This + is easier to understand if you think about the Java object model and how + a many-to-many relationship in Javais created: </para> <programlisting><![CDATA[ @@ -889,7 +897,7 @@ </para> <para> - You may define a bidirectional one-to-many association by mapping a one-to-many association + You can define a bidirectional one-to-many association by mapping a one-to-many association to the same table column(s) as a many-to-one association and declaring the many-valued end <literal>inverse="true"</literal>. </para> @@ -913,8 +921,8 @@ </class>]]></programlisting> <para> - Mapping one end of an association with <literal>inverse="true"</literal> doesn't - affect the operation of cascades, these are orthogonal concepts! + Mapping one end of an association with <literal>inverse="true"</literal> does not + affect the operation of cascades as these are orthogonal concepts. </para> </sect2> @@ -923,8 +931,8 @@ <title>Bidirectional associations with indexed collections</title> <para> A bidirectional association where one end is represented as a <literal>&lt;list&gt;</literal> - or <literal>&lt;map&gt;</literal> requires special consideration. If there is a property of - the child class which maps to the index column, no problem, we can continue using + or <literal>&lt;map&gt;</literal>, requires special consideration. If there is a property of + the child class that maps to the index column you can use <literal>inverse="true"</literal> on the collection mapping: </para> @@ -951,10 +959,10 @@ </class>]]></programlisting> <para> - But, if there is no such property on the child class, we can't think of the association as - truly bidirectional (there is information available at one end of the association that is - not available at the other end). In this case, we can't map the collection - <literal>inverse="true"</literal>. Instead, we could use the following mapping: + If there is no such property on the child class, the association cannot be considered + truly bidirectional. That is, there is information available at one end of the association that is + not available at the other end. In this case, you cannot map the collection + <literal>inverse="true"</literal>. Instead, you could use the following mapping: </para> <programlisting><![CDATA[<class name="Parent"> @@ -982,7 +990,7 @@ <para> Note that in this mapping, the collection-valued end of the association is responsible for - updates to the foreign key. TODO: Does this really result in some unnecessary update statements? + updates to the foreign key. <!--TODO: Does this really result in some unnecessary update statements?--> </para> </sect2> @@ -991,7 +999,7 @@ <title>Ternary associations</title> <para> - There are three possible approaches to mapping a ternary association. One is to use a + There are three possible approaches to mapping a ternary association. One approach is to use a <literal>Map</literal> with an association as its index: </para> @@ -1008,12 +1016,12 @@ </map>]]></programlisting> <para> - A second approach is to simply remodel the association as an entity class. This - is the approach we use most commonly. + A second approach is to remodel the association as an entity class. This + is the most common approach. </para> <para> - A final alternative is to use composite elements, which we will discuss later. + A final alternative is to use composite elements, which will be discussed later. </para> </sect2> @@ -1022,19 +1030,18 @@ <title><literal>Using an &lt;idbag&gt;</literal></title> <para> - If you've fully embraced our view that composite keys are a bad thing and that - entities should have synthetic identifiers (surrogate keys), then you might - find it a bit odd that the many to many associations and collections of values - that we've shown so far all map to tables with composite keys! Now, this point - is quite arguable; a pure association table doesn't seem to benefit much from - a surrogate key (though a collection of composite values <emphasis>might</emphasis>). - Nevertheless, Hibernate provides a feature that allows you to map many to many + The majority of the many-to-many associations and collections of values + shown previously all map to tables with composite keys, even though it has been have suggested + that entities should have synthetic identifiers (surrogate keys). A + pure association table does not seem to benefit much from + a surrogate key, although a collection of composite values <emphasis>might</emphasis>. + It is for this reason that Hibernate provides a feature that allows you to map many-to-many associations and collections of values to a table with a surrogate key. </para> <para> The <literal>&lt;idbag&gt;</literal> element lets you map a <literal>List</literal> - (or <literal>Collection</literal>) with bag semantics. + (or <literal>Collection</literal>) with bag semantics. For example: </para> <programlisting><![CDATA[<idbag name="lovers" table="LOVERS"> @@ -1046,17 +1053,16 @@ </idbag>]]></programlisting> <para> - As you can see, an <literal>&lt;idbag&gt;</literal> has a synthetic id generator, - just like an entity class! A different surrogate key is assigned to each collection - row. Hibernate does not provide any mechanism to discover the surrogate key value - of a particular row, however. + An <literal>&lt;idbag&gt;</literal> has a synthetic id generator, + just like an entity class. A different surrogate key is assigned to each collection + row. Hibernate does not, however, provide any mechanism for discovering the surrogate key value + of a particular row. </para> <para> - Note that the update performance of an <literal>&lt;idbag&gt;</literal> is - <emphasis>much</emphasis> better than a regular <literal>&lt;bag&gt;</literal>! + The update performance of an <literal>&lt;idbag&gt;</literal> supersedes a regular <literal>&lt;bag&gt;</literal>. Hibernate can locate individual rows efficiently and update or delete them - individually, just like a list, map or set. + individually, similar to a list, map or set. </para> <para> @@ -1086,8 +1092,11 @@ <title>Collection examples</title> <para> - The previous sections are pretty confusing. So lets look at an example. This - class: + This section covers collection examples. + </para> + + <para> + The following class has a collection of <literal>Child</literal> instances: </para> <programlisting><![CDATA[package eg; @@ -1108,9 +1117,9 @@ }]]></programlisting> <para> - has a collection of <literal>Child</literal> instances. If each - child has at most one parent, the most natural mapping is a + If each child has, at most, one parent, the most natural mapping is a one-to-many association: + </para> <programlisting><![CDATA[<hibernate-mapping> @@ -1181,7 +1190,7 @@ alter table child add constraint childfk0 (parent_id) references parent]]></programlisting> <para> - Alternatively, if you absolutely insist that this association should be unidirectional, + Alternatively, if this association must be unidirectional you can declare the <literal>NOT NULL</literal> constraint on the <literal>&lt;key&gt;</literal> mapping: </para> @@ -1208,7 +1217,7 @@ </hibernate-mapping>]]></programlisting> <para> - On the other hand, if a child might have multiple parents, a many-to-many + On the other hand, if a child has multiple parents, a many-to-many association is appropriate: </para> @@ -1246,12 +1255,12 @@ alter table childset add constraint childsetfk1 (child_id) references child]]></programlisting> <para> - For more examples and a complete walk-through a parent/child relationship mapping, - see <xref linkend="example-parentchild"/>. + For more examples and a complete explanation of a parent/child relationship mapping, + see <xref linkend="example-parentchild"/> for more information. </para> <para> - Even more exotic association mappings are possible, we will catalog all possibilities + Even more complex association mappings are covered in the next chapter. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/component_mapping.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/component_mapping.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/component_mapping.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -29,17 +29,17 @@ <title>Component Mapping</title> <para> - The notion of a <emphasis>component</emphasis> is re-used in several different contexts, - for different purposes, throughout Hibernate. + The notion of a <emphasis>component</emphasis> is re-used in several different contexts and purposes + throughout Hibernate. </para> <sect1 id="components-dependentobjects" revision="2" > <title>Dependent objects</title> <para> - A component is a contained object that is persisted as a value type, not an entity + A component is a contained object that is persisted as a value type and not an entity reference. The term "component" refers to the object-oriented notion of composition - (not to architecture-level components). For example, you might model a person like this: + and not to architecture-level components. For example, you can model a person like this: </para> <programlisting><![CDATA[public class Person { @@ -93,14 +93,14 @@ }]]></programlisting> <para> - Now <literal>Name</literal> may be persisted as a component of - <literal>Person</literal>. Notice that <literal>Name</literal> defines getter - and setter methods for its persistent properties, but doesn't need to declare + Now <literal>Name</literal> can be persisted as a component of + <literal>Person</literal>. <literal>Name</literal> defines getter + and setter methods for its persistent properties, but it does not need to declare any interfaces or identifier properties. </para> <para> - Our Hibernate mapping would look like: + Our Hibernate mapping would look like this: </para> <programlisting><![CDATA[<class name="eg.Person" table="person"> @@ -124,18 +124,17 @@ </para> <para> - Like all value types, components do not support shared references. In other words, two + Like value types, components do not support shared references. In other words, two persons could have the same name, but the two person objects would contain two independent - name ojects, only "the same" by value. The null value semantics of a component are + name objects that were only "the same" by value. The null value semantics of a component are <emphasis>ad hoc</emphasis>. When reloading the containing object, Hibernate will assume - that if all component columns are null, then the entire component is null. This should - be okay for most purposes. + that if all component columns are null, then the entire component is null. This is suitable for most purposes. </para> <para> - The properties of a component may be of any Hibernate type (collections, many-to-one + The properties of a component can be of any Hibernate type (collections, many-to-one associations, other components, etc). Nested components should <emphasis>not</emphasis> - be considered an exotic usage. Hibernate is intended to support a very fine-grained + be considered an exotic usage. Hibernate is intended to support a fine-grained object model. </para> @@ -164,10 +163,10 @@ <title>Collections of dependent objects</title> <para> - Collections of components are supported (eg. an array of type + Collections of components are supported (e.g. an array of type <literal>Name</literal>). Declare your component collection by replacing the <literal>&lt;element&gt;</literal> tag with a - <literal>&lt;composite-element&gt;</literal> tag. + <literal>&lt;composite-element&gt;</literal> tag: </para> <programlisting><![CDATA[<set name="someNames" table="some_names" lazy="true"> @@ -179,29 +178,31 @@ </composite-element> </set>]]></programlisting> - <para> - Note: if you define a <literal>Set</literal> of composite elements, it is - very important to implement <literal>equals()</literal> and + <important> + <para> + If you define a <literal>Set</literal> of composite elements, it is + important to implement <literal>equals()</literal> and <literal>hashCode()</literal> correctly. - </para> + </important> + </para> <para> - Composite elements may contain components but not collections. If your - composite element itself contains + Composite elements can contain components but not collections. If your + composite element contains components, use the <literal>&lt;nested-composite-element&gt;</literal> - tag. This is a pretty exotic case - a collection of components which - themselves have components. By this stage you should be asking yourself - if a one-to-many association is more appropriate. Try remodelling the - composite element as an entity - but note that even though the Java model + tag. This case is a collection of components which + themselves have components. You may want to consider if + a one-to-many association is more appropriate. Remodel the + composite element as an entity, but be aware that even though the Java model is the same, the relational model and persistence semantics are still slightly different. </para> <para> - Please note that a composite element mapping doesn't support null-able properties - if you're using a <literal>&lt;set&gt;</literal>. Hibernate - has to use each columns value to identify a record when deleting objects - (there is no separate primary key column in the composite element table), + A composite element mapping does not support null-able properties + if you are using a <literal>&lt;set&gt;</literal>. There is no separate primary key column + in the composite element table. Hibernate + uses each column's value to identify a record when deleting objects, which is not possible with null values. You have to either use only not-null properties in a composite-element or choose a <literal>&lt;list&gt;</literal>, <literal>&lt;map&gt;</literal>, @@ -210,10 +211,10 @@ <para> A special case of a composite element is a composite element with a nested - <literal>&lt;many-to-one&gt;</literal> element. A mapping like this allows + <literal>&lt;many-to-one&gt;</literal> element. This mapping allows you to map extra columns of a many-to-many association table to the composite element class. The following is a many-to-many association - from <literal>Order</literal> to <literal>Item</literal> where + from <literal>Order</literal> to <literal>Item</literal>, where <literal>purchaseDate</literal>, <literal>price</literal> and <literal>quantity</literal> are properties of the association: </para> @@ -232,10 +233,10 @@ </class>]]></programlisting> <para> - Of course, there can't be a reference to the purchae on the other side, for - bidirectional association navigation. Remember that components are value types and - don't allow shared references. A single <literal>Purchase</literal> can be in the - set of an <literal>Order</literal>, but it can't be referenced by the <literal>Item</literal> + There cannot be a reference to the purchase on the other side for + bidirectional association navigation. Components are value types and + do not allow shared references. A single <literal>Purchase</literal> can be in the + set of an <literal>Order</literal>, but it cannot be referenced by the <literal>Item</literal> at the same time. </para> @@ -253,7 +254,7 @@ </class>]]></programlisting> <para> - Composite elements may appear in queries using the same syntax as + Composite elements can appear in queries using the same syntax as associations to other entities. </para> @@ -263,8 +264,8 @@ <title>Components as Map indices</title> <para> - The <literal>&lt;composite-map-key&gt;</literal> element lets you map a - component class as the key of a <literal>Map</literal>. Make sure you override + The <literal>&lt;composite-map-key&gt;</literal> element allows you to map a + component class as the key of a <literal>Map</literal>. Ensure that you override <literal>hashCode()</literal> and <literal>equals()</literal> correctly on the component class. </para> @@ -274,7 +275,7 @@ <title>Components as composite identifiers</title> <para> - You may use a component as an identifier of an entity class. Your component + You can use a component as an identifier of an entity class. Your component class must satisfy certain requirements: </para> @@ -287,25 +288,28 @@ <listitem> <para> It must re-implement <literal>equals()</literal> and - <literal>hashCode()</literal>, consistently with the database's + <literal>hashCode()</literal> consistently with the database's notion of composite key equality. </para> </listitem> </itemizedlist> + <note> + <title>Note</title> <para> - <emphasis>Note: in Hibernate3, the second requirement is not an absolutely hard - requirement of Hibernate. But do it anyway.</emphasis> + In Hibernate3, although the second requirement is not an absolutely hard + requirement of Hibernate, it is recommended. </para> - - <para> - You can't use an <literal>IdentifierGenerator</literal> to generate composite keys. + </note> + + <para> + You cannot use an <literal>IdentifierGenerator</literal> to generate composite keys. Instead the application must assign its own identifiers. </para> <para> - Use the <literal>&lt;composite-id&gt;</literal> tag (with nested - <literal>&lt;key-property&gt;</literal> elements) in place of the usual + Use the <literal>&lt;composite-id&gt;</literal> tag, with nested + <literal>&lt;key-property&gt;</literal> elements, in place of the usual <literal>&lt;id&gt;</literal> declaration. For example, the <literal>OrderLine</literal> class has a primary key that depends upon the (composite) primary key of <literal>Order</literal>. @@ -331,9 +335,9 @@ </class>]]></programlisting> <para> - Now, any foreign keys referencing the <literal>OrderLine</literal> table are also - composite. You must declare this in your mappings for other classes. An association - to <literal>OrderLine</literal> would be mapped like this: + Any foreign keys referencing the <literal>OrderLine</literal> table are now + composite. Declare this in your mappings for other classes. An association + to <literal>OrderLine</literal> is mapped like this: </para> <programlisting><![CDATA[<many-to-one name="orderLine" class="OrderLine"> @@ -343,12 +347,17 @@ <column name="customerId"/> </many-to-one>]]></programlisting> - <para> - (Note that the <literal>&lt;column&gt;</literal> tag is an alternative to the - <literal>column</literal> attribute everywhere.) + <note> + </title> + Note + </title> + <para> + The <literal>&lt;column&gt;</literal> tag is an alternative to the + <literal>column</literal> attribute everywhere. </para> + </note> - <para> +<para> A <literal>many-to-many</literal> association to <literal>OrderLine</literal> also uses the composite foreign key: </para> @@ -376,7 +385,7 @@ </set>]]></programlisting> <para> - (The <literal>&lt;one-to-many&gt;</literal> element, as usual, declares no columns.) + The <literal>&lt;one-to-many&gt;</literal> element declares no columns. </para> <para> @@ -406,7 +415,7 @@ <title>Dynamic components</title> <para> - You may even map a property of type <literal>Map</literal>: + You can also map a property of type <literal>Map</literal>: </para> <programlisting><![CDATA[<dynamic-component name="userAttributes"> @@ -418,9 +427,9 @@ <para> The semantics of a <literal>&lt;dynamic-component&gt;</literal> mapping are identical to <literal>&lt;component&gt;</literal>. The advantage of this kind of mapping is - the ability to determine the actual properties of the bean at deployment time, just + the ability to determine the actual properties of the bean at deployment time just by editing the mapping document. Runtime manipulation of the mapping document is - also possible, using a DOM parser. Even better, you can access (and change) Hibernate's + also possible, using a DOM parser. You can also access, and change, Hibernate's configuration-time metamodel via the <literal>Configuration</literal> object. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/configuration.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/configuration.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/configuration.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -29,11 +29,11 @@ <title>Configuration</title> <para> - Because Hibernate is designed to operate in many different environments, there - are a large number of configuration parameters. Fortunately, most have sensible + Hibernate is designed to operate in many different environments and, as such, there + is a broad range of configuration parameters. Fortunately, most have sensible default values and Hibernate is distributed with an example - <literal>hibernate.properties</literal> file in <literal>etc/</literal> that shows - the various options. Just put the example file in your classpath and customize it. + <literal>hibernate.properties</literal> file in <literal>etc/</literal> that displays + the various options. Simply put the example file in your classpath and customize it to suit your needs. </para> <sect1 id="configuration-programmatic" revision="1"> @@ -42,14 +42,14 @@ <para> An instance of <classname>org.hibernate.cfg.Configuration</classname> represents an entire set of mappings of an application's Java types to an SQL database. The <classname>org.hibernate.cfg.Configuration</classname> - is used to build an (immutable) <interfacename>org.hibernate.SessionFactory</interfacename>. The mappings + is used to build an immutable <interfacename>org.hibernate.SessionFactory</interfacename>. The mappings are compiled from various XML mapping files. </para> <para> - You may obtain a <classname>org.hibernate.cfg.Configuration</classname> instance by instantiating + You can obtain a <classname>org.hibernate.cfg.Configuration</classname> instance by instantiating it directly and specifying XML mapping documents. If the mapping files are in the classpath, - use <literal>addResource()</literal>: + use <literal>addResource()</literal>. For example: </para> <programlisting><![CDATA[Configuration cfg = new Configuration() @@ -57,8 +57,8 @@ .addResource("Bid.hbm.xml");]]></programlisting> <para> - An alternative (sometimes better) way is to specify the mapped class, and - let Hibernate find the mapping document for you: + An alternative way is to specify the mapped class and + allow Hibernate to find the mapping document for you: </para> <programlisting><![CDATA[Configuration cfg = new Configuration() @@ -66,14 +66,14 @@ .addClass(org.hibernate.auction.Bid.class);]]></programlisting> <para> - Then Hibernate will look for mapping files named <filename>/org/hibernate/auction/Item.hbm.xml</filename> + Hibernate will then search for mapping files named <filename>/org/hibernate/auction/Item.hbm.xml</filename> and <filename>/org/hibernate/auction/Bid.hbm.xml</filename> in the classpath. This approach eliminates any hardcoded filenames. </para> <para> A <classname>org.hibernate.cfg.Configuration</classname> also allows you to specify configuration - properties: + properties. For example: </para> <programlisting><![CDATA[Configuration cfg = new Configuration() @@ -85,7 +85,7 @@ <para> This is not the only way to pass configuration properties to Hibernate. - The various options include: + Some alternative options include: </para> <orderedlist spacing="compact"> @@ -108,18 +108,18 @@ <listitem> <para> Include <literal>&lt;property&gt;</literal> elements in - <literal>hibernate.cfg.xml</literal> (discussed later). + <literal>hibernate.cfg.xml</literal> (this is discussed later). </para> </listitem> </orderedlist> <para> - <filename>hibernate.properties</filename> is the easiest approach if you want to get started quickly. + If you want to get started quickly<filename>hibernate.properties</filename> is the easiest approach. </para> <para> - The <classname>org.hibernate.cfg.Configuration</classname> is intended as a startup-time object, - to be discarded once a <literal>SessionFactory</literal> is created. + The <classname>org.hibernate.cfg.Configuration</classname> is intended as a startup-time object that will + be discarded once a <literal>SessionFactory</literal> is created. </para> </sect1> @@ -147,7 +147,7 @@ <title>JDBC connections</title> <para> - Usually, you want to have the <interfacename>org.hibernate.SessionFactory</interfacename> create and pool + It is advisable to have the <interfacename>org.hibernate.SessionFactory</interfacename> create and pool JDBC connections for you. If you take this approach, opening a <interfacename>org.hibernate.Session</interfacename> is as simple as: </para> @@ -155,18 +155,18 @@ <programlisting><![CDATA[Session session = sessions.openSession(); // open a new Session]]></programlisting> <para> - As soon as you do something that requires access to the database, a JDBC connection will be obtained from + Once you start a task that requires access to the database, a JDBC connection will be obtained from the pool. </para> <para> - For this to work, we need to pass some JDBC connection properties to Hibernate. All Hibernate property - names and semantics are defined on the class <classname>org.hibernate.cfg.Environment</classname>. We will - now describe the most important settings for JDBC connection configuration. + Before you can do this, you first need to pass some JDBC connection properties to Hibernate. All Hibernate property + names and semantics are defined on the class <classname>org.hibernate.cfg.Environment</classname>. + The most important settings for JDBC connection configuration are outlined below. </para> <para> - Hibernate will obtain (and pool) connections using <classname>java.sql.DriverManager</classname> + Hibernate will obtain and pool connections using <classname>java.sql.DriverManager</classname> if you set the following properties: </para> @@ -227,25 +227,25 @@ </table> <para> - Hibernate's own connection pooling algorithm is however quite rudimentary. + Hibernate's own connection pooling algorithm is, however, quite rudimentary. It is intended to help you get started and is <emphasis>not intended for use - in a production system</emphasis> or even for performance testing. You should + in a production system</emphasis>, or even for performance testing. You should use a third party pool for best performance and stability. Just replace the <property>hibernate.connection.pool_size</property> property with connection pool specific settings. This will turn off Hibernate's internal pool. For - example, you might like to use C3P0. + example, you might like to use c3p0. </para> <para> C3P0 is an open source JDBC connection pool distributed along with Hibernate in the <filename>lib</filename> directory. Hibernate will use its <classname>org.hibernate.connection.C3P0ConnectionProvider</classname> - for connection pooling if you set <property>hibernate.c3p0.*</property> properties. If you'd like to use Proxool + for connection pooling if you set <property>hibernate.c3p0.*</property> properties. If you would like to use Proxool, refer to the packaged <filename>hibernate.properties</filename> and the Hibernate web site for more information. </para> <para> - Here is an example <filename>hibernate.properties</filename> file for C3P0: + The following is an example <filename>hibernate.properties</filename> file for c3p0: </para> <programlisting id="c3p0-configuration" revision="1"><![CDATA[hibernate.connection.driver_class = org.postgresql.Driver @@ -260,7 +260,7 @@ <para> For use inside an application server, you should almost always configure Hibernate to obtain connections - from an application server <interfacename>javax.sql.Datasource</interfacename> registered in JNDI. You'll + from an application server <interfacename>javax.sql.Datasource</interfacename> registered in JNDI. You will need to set at least one of the following properties: </para> @@ -321,7 +321,7 @@ </table> <para> - Here's an example <filename>hibernate.properties</filename> file for an application server provided JNDI + Here is an example <filename>hibernate.properties</filename> file for an application server provided JNDI datasource: </para> @@ -338,13 +338,13 @@ </para> <para> - Arbitrary connection properties may be given by prepending "<literal>hibernate.connection</literal>" to the - connection property name. For example, you may specify a <property>charSet</property> + Arbitrary connection properties can be given by prepending "<literal>hibernate.connection</literal>" to the + connection property name. For example, you can specify a <property>charSet</property> connection property using <property>hibernate.connection.charSet</property>. </para> <para> - You may define your own plugin strategy for obtaining JDBC connections by implementing the + You can define your own plugin strategy for obtaining JDBC connections by implementing the interface <interfacename>org.hibernate.connection.ConnectionProvider</interfacename>, and specifying your custom implementation via the <property>hibernate.connection.provider_class</property> property. </para> @@ -355,14 +355,14 @@ <title>Optional configuration properties</title> <para> - There are a number of other properties that control the behaviour of Hibernate at runtime. All are optional + There are a number of other properties that control the behavior of Hibernate at runtime. All are optional and have reasonable default values. </para> <para> - <emphasis>Warning: some of these properties are "system-level" only.</emphasis> System-level properties can + <warning><emphasis>Some of these properties are "system-level" only.</emphasis> System-level properties can be set only via <literal>java -Dproperty=value</literal> or <filename>hibernate.properties</filename>. They - may <emphasis>not</emphasis> be set by the other techniques described above. + <emphasis>cannot</emphasis> be set by the other techniques described above.</warning> </para> <table frame="topbot" id="configuration-optional-properties" revision="8"> @@ -385,12 +385,12 @@ The classname of a Hibernate <classname>org.hibernate.dialect.Dialect</classname> which allows Hibernate to generate SQL optimized for a particular relational database. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>full.classname.of.Dialect</literal> </para> <para> - In most cases Hibernate will actually be able to chose the correct - <classname>org.hibernate.dialect.Dialect</classname> implementation to use based on the + In most cases Hibernate will actually be able to choose the correct + <classname>org.hibernate.dialect.Dialect</classname> implementation based on the <literal>JDBC metadata</literal> returned by the JDBC driver. </para> </entry> @@ -404,7 +404,7 @@ to setting the log category <literal>org.hibernate.SQL</literal> to <literal>debug</literal>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -416,7 +416,7 @@ <entry> Pretty print the SQL in the log and console. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -429,7 +429,7 @@ Qualify unqualified table names with the given schema/tablespace in generated SQL. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>SCHEMA_NAME</literal> </para> </entry> @@ -439,10 +439,10 @@ <property>hibernate.default_catalog</property> </entry> <entry> - Qualify unqualified table names with the given catalog + Qualifies unqualified table names with the given catalog in generated SQL. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>CATALOG_NAME</literal> </para> </entry> @@ -455,7 +455,7 @@ The <interfacename>org.hibernate.SessionFactory</interfacename> will be automatically bound to this name in JNDI after it has been created. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>jndi/composite/name</literal> </para> </entry> @@ -465,11 +465,11 @@ <property>hibernate.max_fetch_depth</property> </entry> <entry> - Set a maximum "depth" for the outer join fetch tree + Sets a maximum "depth" for the outer join fetch tree for single-ended associations (one-to-one, many-to-one). A <literal>0</literal> disables default outer join fetching. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> recommended values between <literal>0</literal> and <literal>3</literal> </para> @@ -480,9 +480,9 @@ <property>hibernate.default_batch_fetch_size</property> </entry> <entry> - Set a default size for Hibernate batch fetching of associations. + Sets a default size for Hibernate batch fetching of associations. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> recommended values <literal>4</literal>, <literal>8</literal>, <literal>16</literal> </para> @@ -493,7 +493,7 @@ <property>hibernate.default_entity_mode</property> </entry> <entry> - Set a default mode for entity representation for all sessions + Sets a default mode for entity representation for all sessions opened from this <literal>SessionFactory</literal> <para> <literal>dynamic-map</literal>, <literal>dom4j</literal>, @@ -506,11 +506,11 @@ <property>hibernate.order_updates</property> </entry> <entry> - Force Hibernate to order SQL updates by the primary key value + Forces Hibernate to order SQL updates by the primary key value of the items being updated. This will result in fewer transaction deadlocks in highly concurrent systems. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -523,7 +523,7 @@ If enabled, Hibernate will collect statistics useful for performance tuning. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -536,7 +536,7 @@ If enabled, generated identifier properties will be reset to default values when objects are deleted. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -549,7 +549,7 @@ If turned on, Hibernate will generate comments inside the SQL, for easier debugging, defaults to <literal>false</literal>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -588,7 +588,7 @@ <entry> A non-zero value enables use of JDBC2 batch updates by Hibernate. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> recommended values between <literal>5</literal> and <literal>30</literal> </para> </entry> @@ -599,11 +599,11 @@ </entry> <entry> Set this property to <literal>true</literal> if your JDBC driver returns - correct row counts from <literal>executeBatch()</literal> (it is usually - safe to turn this option on). Hibernate will then use batched DML for + correct row counts from <literal>executeBatch()</literal>. Iit is usually + safe to turn this option on. Hibernate will then use batched DML for automatically versioned data. Defaults to <literal>false</literal>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -616,7 +616,7 @@ Select a custom <interfacename>org.hibernate.jdbc.Batcher</interfacename>. Most applications will not need this configuration property. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>classname.of.BatcherFactory</literal> </para> </entry> @@ -627,10 +627,10 @@ </entry> <entry> Enables use of JDBC2 scrollable resultsets by Hibernate. - This property is only necessary when using user supplied - JDBC connections, Hibernate uses connection metadata otherwise. + This property is only necessary when using user-supplied + JDBC connections. Hibernate uses connection metadata otherwise. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -643,7 +643,7 @@ Use streams when writing/reading <literal>binary</literal> or <literal>serializable</literal> types to/from JDBC. <emphasis>*system-level property*</emphasis> <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -653,13 +653,13 @@ <property>hibernate.jdbc.use_get_generated_keys</property> </entry> <entry> - Enable use of JDBC3 <literal>PreparedStatement.getGeneratedKeys()</literal> + Enables use of JDBC3 <literal>PreparedStatement.getGeneratedKeys()</literal> to retrieve natively generated keys after insert. Requires JDBC3+ driver and JRE1.4+, set to false if your driver has problems with the Hibernate - identifier generators. By default, tries to determine the driver capabilities + identifier generators. By default, it tries to determine the driver capabilities using connection metadata. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true|false</literal> </para> </entry> @@ -672,7 +672,7 @@ The classname of a custom <interfacename>org.hibernate.connection.ConnectionProvider</interfacename> which provides JDBC connections to Hibernate. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>classname.of.ConnectionProvider</literal> </para> </entry> @@ -682,11 +682,11 @@ <property>hibernate.connection.isolation</property> </entry> <entry> - Set the JDBC transaction isolation level. Check <interfacename>java.sql.Connection</interfacename> - for meaningful values but note that most databases do not support all isolation levels and some + Sets the JDBC transaction isolation level. Check <interfacename>java.sql.Connection</interfacename> + for meaningful values, but note that most databases do not support all isolation levels and some define additional, non-standard isolations. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>1, 2, 4, 8</literal> </para> </entry> @@ -696,9 +696,9 @@ <property>hibernate.connection.autocommit</property> </entry> <entry> - Enables autocommit for JDBC pooled connections (not recommended). + Enables autocommit for JDBC pooled connections (it is not recommended). <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -708,9 +708,9 @@ <property>hibernate.connection.release_mode</property> </entry> <entry> - Specify when Hibernate should release JDBC connections. By default, + Specifies when Hibernate should release JDBC connections. By default, a JDBC connection is held until the session is explicitly closed or - disconnected. For an application server JTA datasource, you should use + disconnected. For an application server JTA datasource, use <literal>after_statement</literal> to aggressively release connections after every JDBC call. For a non-JTA connection, it often makes sense to release the connection at the end of each transaction, by using @@ -719,12 +719,12 @@ strategies and <literal>after_transaction</literal> for the JDBC transaction strategy. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>auto</literal> (default) | <literal>on_close</literal> | <literal>after_transaction</literal> | <literal>after_statement</literal> </para> <para> - Note that this setting only affects <literal>Session</literal>s returned from + This setting only affects <literal>Session</literal>s returned from <literal>SessionFactory.openSession</literal>. For <literal>Session</literal>s obtained through <literal>SessionFactory.getCurrentSession</literal>, the <literal>CurrentSessionContext</literal> implementation configured for use @@ -774,7 +774,7 @@ <entry> The classname of a custom <literal>CacheProvider</literal>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>classname.of.CacheProvider</literal> </para> </entry> @@ -784,12 +784,12 @@ <literal>hibernate.cache.use_minimal_puts</literal> </entry> <entry> - Optimize second-level cache operation to minimize writes, at the + Optimizes second-level cache operation to minimize writes, at the cost of more frequent reads. This setting is most useful for clustered caches and, in Hibernate3, is enabled by default for clustered cache implementations. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true|false</literal> </para> </entry> @@ -799,9 +799,9 @@ <literal>hibernate.cache.use_query_cache</literal> </entry> <entry> - Enable the query cache, individual queries still have to be set cachable. + Enables the query cache. Individual queries still have to be set cachable. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true|false</literal> </para> </entry> @@ -811,11 +811,11 @@ <literal>hibernate.cache.use_second_level_cache</literal> </entry> <entry> - May be used to completely disable the second level cache, which is enabled + Can be used to completely disable the second level cache, which is enabled by default for classes which specify a <literal>&lt;cache&gt;</literal> mapping. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true|false</literal> </para> </entry> @@ -828,7 +828,7 @@ The classname of a custom <literal>QueryCache</literal> interface, defaults to the built-in <literal>StandardQueryCache</literal>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>classname.of.QueryCache</literal> </para> </entry> @@ -840,7 +840,7 @@ <entry> A prefix to use for second-level cache region names. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>prefix</literal> </para> </entry> @@ -853,7 +853,7 @@ Forces Hibernate to store data in the second-level cache in a more human-friendly format. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true|false</literal> </para> </entry> @@ -883,7 +883,7 @@ to use with Hibernate <literal>Transaction</literal> API (defaults to <literal>JDBCTransactionFactory</literal>). <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>classname.of.TransactionFactory</literal> </para> </entry> @@ -897,7 +897,7 @@ obtain the JTA <literal>UserTransaction</literal> from the application server. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>jndi/composite/name</literal> </para> </entry> @@ -907,11 +907,11 @@ <literal>hibernate.transaction.manager_lookup_class</literal> </entry> <entry> - The classname of a <literal>TransactionManagerLookup</literal> - - required when JVM-level caching is enabled or when using hilo + The classname of a <literal>TransactionManagerLookup</literal>. It is + required when JVM-level caching is enabled or when using hilo generator in a JTA environment. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>classname.of.TransactionManagerLookup</literal> </para> </entry> @@ -926,7 +926,7 @@ automatic session context management is preferred, see <xref linkend="architecture-current-session"/>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -938,10 +938,10 @@ <entry> If enabled, the session will be automatically closed during the after completion phase of the transaction. Built-in and - utomatic session context management is preferred, see + automatic session context management is preferred, see <xref linkend="architecture-current-session"/>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -967,12 +967,12 @@ <literal>hibernate.current_session_context_class</literal> </entry> <entry> - Supply a (custom) strategy for the scoping of the "current" + Supply a custom strategy for the scoping of the "current" <literal>Session</literal>. See <xref linkend="architecture-current-session"/> for more information about the built-in strategies. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>jta</literal> | <literal>thread</literal> | <literal>managed</literal> | <literal>custom.Class</literal> </para> @@ -985,7 +985,7 @@ <entry> Chooses the HQL parser implementation. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>org.hibernate.hql.ast.ASTQueryTranslatorFactory</literal> or <literal>org.hibernate.hql.classic.ClassicQueryTranslatorFactory</literal> </para> @@ -996,10 +996,10 @@ <literal>hibernate.query.substitutions</literal> </entry> <entry> - Mapping from tokens in Hibernate queries to SQL tokens + Is used to map from tokens in Hibernate queries to SQL tokens (tokens might be function or literal names, for example). <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>hqlLiteral=SQL_LITERAL, hqlFunction=SQLFUNC</literal> </para> </entry> @@ -1009,13 +1009,13 @@ <literal>hibernate.hbm2ddl.auto</literal> </entry> <entry> - Automatically validate or export schema DDL to the database + Automatically validates or exports schema DDL to the database when the <literal>SessionFactory</literal> is created. With <literal>create-drop</literal>, the database schema will be dropped when the <literal>SessionFactory</literal> is closed explicitly. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>validate</literal> | <literal>update</literal> | <literal>create</literal> | <literal>create-drop</literal> </para> @@ -1026,12 +1026,12 @@ <literal>hibernate.cglib.use_reflection_optimizer</literal> </entry> <entry> - Enables use of CGLIB instead of runtime reflection (System-level - property). Reflection can sometimes be useful when troubleshooting, - note that Hibernate always requires CGLIB even if you turn off the - optimizer. You can not set this property in <literal>hibernate.cfg.xml</literal>. + Enables the use of CGLIB instead of runtime reflection (System-level + property). Reflection can sometimes be useful when troubleshooting. + Hibernate always requires CGLIB even if you turn off the + optimizer. You cannot set this property in <literal>hibernate.cfg.xml</literal>. <para> - <emphasis role="strong">eg.</emphasis> + <emphasis role="strong">e.g.</emphasis> <literal>true</literal> | <literal>false</literal> </para> </entry> @@ -1044,10 +1044,10 @@ <title>SQL Dialects</title> <para> - You should always set the <literal>hibernate.dialect</literal> property to the correct + Always set the <literal>hibernate.dialect</literal> property to the correct <literal>org.hibernate.dialect.Dialect</literal> subclass for your database. If you specify a dialect, Hibernate will use sensible defaults for some of the - other properties listed above, saving you the effort of specifying them manually. + other properties listed above. This means that you will not have to specify them manually. </para> <table frame="topbot" id="sql-dialects" revision="2"> @@ -1142,17 +1142,17 @@ <para> If your database supports ANSI, Oracle or Sybase style outer joins, <emphasis>outer join fetching</emphasis> will often increase performance by limiting the number of round - trips to and from the database (at the cost of possibly more work performed by - the database itself). Outer join fetching allows a whole graph of objects connected + trips to and from the database. This is, however, at the cost of possibly more work performed by + the database itself. Outer join fetching allows a whole graph of objects connected by many-to-one, one-to-many, many-to-many and one-to-one associations to be retrieved in a single SQL <literal>SELECT</literal>. </para> <para> - Outer join fetching may be disabled <emphasis>globally</emphasis> by setting + Outer join fetching can be disabled <emphasis>globally</emphasis> by setting the property <literal>hibernate.max_fetch_depth</literal> to <literal>0</literal>. A setting of <literal>1</literal> or higher enables outer join fetching for - one-to-one and many-to-one associations which have been mapped with + one-to-one and many-to-one associations that have been mapped with <literal>fetch="join"</literal>. </para> @@ -1166,8 +1166,8 @@ <title>Binary Streams</title> <para> - Oracle limits the size of <literal>byte</literal> arrays that may - be passed to/from its JDBC driver. If you wish to use large instances of + Oracle limits the size of <literal>byte</literal> arrays that can + be passed to and/or from its JDBC driver. If you wish to use large instances of <literal>binary</literal> or <literal>serializable</literal> type, you should enable <literal>hibernate.jdbc.use_streams_for_binary</literal>. <emphasis>This is a system-level setting only.</emphasis> @@ -1182,7 +1182,7 @@ The properties prefixed by <literal>hibernate.cache</literal> allow you to use a process or cluster scoped second-level cache system with Hibernate. See the <xref linkend="performance-cache"/> for - more details. + more information. </para> </sect2> @@ -1191,21 +1191,21 @@ <title>Query Language Substitution</title> <para> - You may define new Hibernate query tokens using <literal>hibernate.query.substitutions</literal>. + You can define new Hibernate query tokens using <literal>hibernate.query.substitutions</literal>. For example: </para> <programlisting>hibernate.query.substitutions true=1, false=0</programlisting> <para> - would cause the tokens <literal>true</literal> and <literal>false</literal> to be translated to + This would cause the tokens <literal>true</literal> and <literal>false</literal> to be translated to integer literals in the generated SQL. </para> <programlisting>hibernate.query.substitutions toLowercase=LOWER</programlisting> <para> - would allow you to rename the SQL <literal>LOWER</literal> function. + This would allow you to rename the SQL <literal>LOWER</literal> function. </para> </sect2> @@ -1214,8 +1214,8 @@ <title>Hibernate statistics</title> <para> - If you enable <literal>hibernate.generate_statistics</literal>, Hibernate will - expose a number of metrics that are useful when tuning a running system via + If you enable <literal>hibernate.generate_statistics</literal>, Hibernate + exposes a number of metrics that are useful when tuning a running system via <literal>SessionFactory.getStatistics()</literal>. Hibernate can even be configured to expose these statistics via JMX. Read the Javadoc of the interfaces in <literal>org.hibernate.stats</literal> for more information. @@ -1231,15 +1231,15 @@ Hibernate utilizes <ulink url="http://www.slf4j.org/">Simple Logging Facade for Java</ulink> (SLF4J) in order to log various system events. SLF4J can direct your logging output to several logging frameworks (NOP, Simple, log4j version 1.2, JDK 1.4 logging, JCL or logback) depending on your - chosen binding. In order to setup logging properly you will need <filename>slf4j-api.jar</filename> in + chosen binding. In order to setup logging you will need <filename>slf4j-api.jar</filename> in your classpath together with the jar file for your preferred binding - <filename>slf4j-log4j12.jar</filename> in the case of Log4J. See the SLF4J <ulink url="http://www.slf4j.org/manual.html">documentation</uli... for more detail. - To use Log4j you will also need to place a <filename>log4j.properties</filename> file in your classpath, - an example properties file is distributed with Hibernate in the <literal>src/</literal> directory. + To use Log4j you will also need to place a <filename>log4j.properties</filename> file in your classpath. + An example properties file is distributed with Hibernate in the <literal>src/</literal> directory. </para> <para> - We strongly recommend that you familiarize yourself with Hibernate's log + It is recommended that you familiarize yourself with Hibernate's log messages. A lot of work has been put into making the Hibernate log as detailed as possible, without making it unreadable. It is an essential troubleshooting device. The most interesting log categories are the @@ -1302,8 +1302,8 @@ <row> <entry><literal>org.hibernate</literal></entry> <entry> - Log everything (a lot of information, but very useful for - troubleshooting) + Log everything. This is a lot of information but it is useful for + troubleshooting </entry> </row> </tbody> @@ -1328,7 +1328,7 @@ </para> <para> - You may provide rules for automatically generating database identifiers from + You can provide rules for automatically generating database identifiers from Java identifiers or for processing "logical" column and table names given in the mapping file into "physical" table and column names. This feature helps reduce the verbosity of the mapping document, eliminating repetitive noise @@ -1337,7 +1337,7 @@ </para> <para> - You may specify a different strategy by calling + You can specify a different strategy by calling <literal>Configuration.setNamingStrategy()</literal> before adding mappings: </para> @@ -1365,7 +1365,7 @@ </para> <para> - The XML configuration file is by default expected to be in the root o + The XML configuration file is by default expected to be in the root of your <literal>CLASSPATH</literal>. Here is an example: </para> @@ -1403,22 +1403,22 @@ </hibernate-configuration>]]></programlisting> <para> - As you can see, the advantage of this approach is the externalization of the + The advantage of this approach is the externalization of the mapping file names to configuration. The <literal>hibernate.cfg.xml</literal> - is also more convenient once you have to tune the Hibernate cache. Note that is + is also more convenient once you have to tune the Hibernate cache. It is your choice to use either <literal>hibernate.properties</literal> or - <literal>hibernate.cfg.xml</literal>, both are equivalent, except for the above + <literal>hibernate.cfg.xml</literal>. Both are equivalent, except for the above mentioned benefits of using the XML syntax. </para> <para> - With the XML configuration, starting Hibernate is then as simple as + With the XML configuration, starting Hibernate is then as simple as: </para> <programlisting><![CDATA[SessionFactory sf = new Configuration().configure().buildSessionFactory();]]></programlisting> <para> - You can pick a different XML configuration file using + You can select a different XML configuration file using: </para> <programlisting><![CDATA[SessionFactory sf = new Configuration() @@ -1441,8 +1441,8 @@ JDBC connections managed by the container and provided through JNDI. Usually, a JTA compatible <literal>TransactionManager</literal> and a <literal>ResourceManager</literal> take care of transaction management (CMT), - esp. distributed transaction handling across several datasources. You may - of course also demarcate transaction boundaries programmatically (BMT) or + especially distributed transaction handling across several datasources. You can + also demarcate transaction boundaries programmatically (BMT), or you might want to use the optional Hibernate <literal>Transaction</literal> API for this to keep your code portable. </para> @@ -1461,10 +1461,10 @@ <itemizedlist> <listitem> <para> - <emphasis>JTA Session binding:</emphasis> The Hibernate <literal>Session</literal> - may be automatically bound to the scope of JTA transactions. Simply + <emphasis>JTA Session binding:</emphasis> the Hibernate <literal>Session</literal> + can be automatically bound to the scope of JTA transactions. Simply lookup the <literal>SessionFactory</literal> from JNDI and get the current - <literal>Session</literal>. Let Hibernate take care of flushing and closing the + <literal>Session</literal>. Let Hibernate manage flushing and closing the <literal>Session</literal> when your JTA transaction completes. Transaction demarcation is either declarative (CMT) or programmatic (BMT/UserTransaction). </para> @@ -1474,12 +1474,12 @@ <itemizedlist> <listitem> <para> - <emphasis>JMX deployment:</emphasis> If you have a JMX capable application server - (e.g. JBoss AS), you can chose to deploy Hibernate as a managed MBean. This saves + <emphasis>JMX deployment:</emphasis> if you have a JMX capable application server + (e.g. JBoss AS), you can choose to deploy Hibernate as a managed MBean. This saves you the one line startup code to build your <literal>SessionFactory</literal> from a <literal>Configuration</literal>. The container will startup your - <literal>HibernateService</literal>, and ideally also take care of service - dependencies (Datasource has to be available before Hibernate starts, etc). + <literal>HibernateService</literal> and also take care of service + dependencies (datasource has to be available before Hibernate starts, etc). </para> </listitem> </itemizedlist> @@ -1495,8 +1495,8 @@ <para> The Hibernate <literal>Session</literal> API is independent of any transaction - demarcation system in your architecture. If you let Hibernate use JDBC directly, - through a connection pool, you may begin and end your transactions by calling + demarcation system in your architecture. If you let Hibernate use JDBC directly + through a connection pool, you can begin and end your transactions by calling the JDBC API. If you run in a J2EE application server, you might want to use bean-managed transactions and call the JTA API and <literal>UserTransaction</literal> when needed. </para> @@ -1509,7 +1509,7 @@ </para> <para> - There are three standard (built-in) choices: + There are three standard, or built-in, choices: </para> <variablelist spacing="compact"> @@ -1523,9 +1523,9 @@ <term><literal>org.hibernate.transaction.JTATransactionFactory</literal></term> <listitem> <para> - delegates to container-managed transaction if an existing transaction is - underway in this context (e.g. EJB session bean method), otherwise - a new transaction is started and bean-managed transaction are used. + delegates to container-managed transactions if an existing transaction is + underway in this context (for example, EJB session bean method). Otherwise, + a new transaction is started and bean-managed transactions are used. </para> </listitem> </varlistentry> @@ -1538,15 +1538,15 @@ </variablelist> <para> - You may also define your own transaction strategies (for a CORBA transaction service, + You can also define your own transaction strategies (for a CORBA transaction service, for example). </para> <para> - Some features in Hibernate (i.e. the second level cache, Contextual Sessions with JTA, etc.) + Some features in Hibernate (i.e., the second level cache, Contextual Sessions with JTA, etc.) require access to the JTA <literal>TransactionManager</literal> in a managed environment. - In an application server you have to specify how Hibernate should obtain a reference to the - <literal>TransactionManager</literal>, since J2EE does not standardize a single mechanism: + In an application server, since J2EE does not standardize a single mechanism, you have to specify how Hibernate should obtain a reference to the + <literal>TransactionManager</literal>: </para> <table frame="topbot" id="jtamanagerlookup" revision="1"> @@ -1611,18 +1611,18 @@ <title>JNDI-bound <literal>SessionFactory</literal></title> <para> - A JNDI bound Hibernate <literal>SessionFactory</literal> can simplify the lookup - of the factory and the creation of new <literal>Session</literal>s. Note that this - is not related to a JNDI bound <literal>Datasource</literal>, both simply use the - same registry! + A JNDI-bound Hibernate <literal>SessionFactory</literal> can simplify the lookup + function of the factory and create new <literal>Session</literal>s. This + is not, however, related to a JNDI bound <literal>Datasource</literal>; both simply use the + same registry. </para> <para> If you wish to have the <literal>SessionFactory</literal> bound to a JNDI namespace, specify - a name (eg. <literal>java:hibernate/SessionFactory</literal>) using the property + a name (e.g. <literal>java:hibernate/SessionFactory</literal>) using the property <literal>hibernate.session_factory_name</literal>. If this property is omitted, the - <literal>SessionFactory</literal> will not be bound to JNDI. (This is especially useful in - environments with a read-only JNDI default implementation, e.g. Tomcat.) + <literal>SessionFactory</literal> will not be bound to JNDI. This is especially useful in + environments with a read-only JNDI default implementation (in Tomcat, for example). </para> <para> @@ -1634,18 +1634,18 @@ <para> Hibernate will automatically place the <literal>SessionFactory</literal> in JNDI after - you call <literal>cfg.buildSessionFactory()</literal>. This means you will at least have - this call in some startup code (or utility class) in your application, unless you use - JMX deployment with the <literal>HibernateService</literal> (discussed later). + you call <literal>cfg.buildSessionFactory()</literal>. This means you will have + this call in some startup code, or utility class in your application, unless you use + JMX deployment with the <literal>HibernateService</literal> (this is discussed later in greater detail). </para> <para> - If you use a JNDI <literal>SessionFactory</literal>, an EJB or any other class may - obtain the <literal>SessionFactory</literal> using a JNDI lookup. + If you use a JNDI <literal>SessionFactory</literal>, an EJB or any other class, you can + obtain the <literal>SessionFactory</literal> using a JNDI lookup. </para> <para> - We recommend that you bind the <literal>SessionFactory</literal> to JNDI in + It is recommended that you bind the <literal>SessionFactory</literal> to JNDI in a managed environment and use a <literal>static</literal> singleton otherwise. To shield your application code from these details, we also recommend to hide the actual lookup code for a <literal>SessionFactory</literal> in a helper class, @@ -1659,15 +1659,15 @@ <title>Current Session context management with JTA</title> <para> - The easiest way to handle <literal>Session</literal>s and transactions is - Hibernates automatic "current" <literal>Session</literal> management. - See the discussion of <link linkend="architecture-current-session">current sessions</link>. + The easiest way to handle <literal>Sessions</literal> and transactions is + Hibernate's automatic "current" <literal>Session</literal> management. + For a discussion of contextual sessions see <link linkend="architecture-current-session"></link>. Using the <literal>"jta"</literal> session context, if there is no Hibernate <literal>Session</literal> associated with the current JTA transaction, one will be started and associated with that JTA transaction the first time you call <literal>sessionFactory.getCurrentSession()</literal>. The <literal>Session</literal>s - retrieved via <literal>getCurrentSession()</literal> in <literal>"jta"</literal> context - will be set to automatically flush before the transaction completes, close + retrieved via <literal>getCurrentSession()</literal> in the<literal>"jta"</literal> context + are set to automatically flush before the transaction completes, close after the transaction completes, and aggressively release JDBC connections after each statement. This allows the <literal>Session</literal>s to be managed by the life cycle of the JTA transaction to which it is associated, @@ -1686,15 +1686,15 @@ <para> The line <literal>cfg.buildSessionFactory()</literal> still has to be executed somewhere to get a <literal>SessionFactory</literal> into JNDI. You can do this - either in a <literal>static</literal> initializer block (like the one in - <literal>HibernateUtil</literal>) or you deploy Hibernate as a <emphasis>managed + either in a <literal>static</literal> initializer block, like the one in + <literal>HibernateUtil</literal>, or you can deploy Hibernate as a <emphasis>managed service</emphasis>. </para> <para> Hibernate is distributed with <literal>org.hibernate.jmx.HibernateService</literal> for deployment on an application server with JMX capabilities, such as JBoss AS. - The actual deployment and configuration is vendor specific. Here is an example + The actual deployment and configuration is vendor-specific. Here is an example <literal>jboss-service.xml</literal> for JBoss 4.0.x: </para> @@ -1746,7 +1746,7 @@ in a JAR file with the extension <literal>.sar</literal> (service archive). You also need to package Hibernate, its required third-party libraries, your compiled persistent classes, as well as your mapping files in the same archive. Your enterprise beans (usually session - beans) may be kept in their own JAR file, but you may include this EJB JAR file in the + beans) can be kept in their own JAR file, but you can include this EJB JAR file in the main service archive to get a single (hot-)deployable unit. Consult the JBoss AS documentation for more information about JMX service and EJB deployment. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/events.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/events.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/events.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -29,9 +29,9 @@ <title>Interceptors and events</title> <para> - It is often useful for the application to react to certain events that occur - inside Hibernate. This allows implementation of certain kinds of generic - functionality, and extension of Hibernate functionality. + It is useful for the application to react to certain events that occur + inside Hibernate. This allows for the implementation of generic + functionality and the extension of Hibernate functionality. </para> <sect1 id="objectstate-interceptors" revision="3"> @@ -39,7 +39,7 @@ <para> The <literal>Interceptor</literal> interface provides callbacks from the session to the - application allowing the application to inspect and/or manipulate properties of a + application, allowing the application to inspect and/or manipulate properties of a persistent object before it is saved, updated, deleted or loaded. One possible use for this is to track auditing information. For example, the following <literal>Interceptor</literal> automatically sets the <literal>createTimestamp</literal> @@ -49,7 +49,7 @@ </para> <para> - You may either implement <literal>Interceptor</literal> directly or (better) extend + You can either implement <literal>Interceptor</literal> directly or extend <literal>EmptyInterceptor</literal>. </para> @@ -137,7 +137,7 @@ }]]></programlisting> <para> - Interceptors come in two flavors: <literal>Session</literal>-scoped and + There are two kinds of inteceptors: <literal>Session</literal>-scoped and <literal>SessionFactory</literal>-scoped. </para> @@ -151,11 +151,11 @@ <para> A <literal>SessionFactory</literal>-scoped interceptor is registered with the <literal>Configuration</literal> - object prior to building the <literal>SessionFactory</literal>. In this case, the supplied interceptor - will be applied to all sessions opened from that <literal>SessionFactory</literal>; this is true unless - a session is opened explicitly specifying the interceptor to use. <literal>SessionFactory</literal>-scoped - interceptors must be thread safe, taking care to not store session-specific state since multiple - sessions will use this interceptor (potentially) concurrently. + object prior to building the <literal>SessionFactory</literal>. Unless + a session is opened explicitly specifying the interceptor to use, the supplied interceptor + will be applied to all sessions opened from that <literal>SessionFactory</literal>. <literal>SessionFactory</literal>-scoped + interceptors must be thread safe. Ensure that you do not store session-specific states, since multiple + sessions will use this interceptor potentially concurrently. </para> <programlisting><![CDATA[new Configuration().setInterceptor( new AuditInterceptor() );]]></programlisting> @@ -166,38 +166,38 @@ <title>Event system</title> <para> - If you have to react to particular events in your persistence layer, you may + If you have to react to particular events in your persistence layer, you can also use the Hibernate3 <emphasis>event</emphasis> architecture. The event - system can be used in addition or as a replacement for interceptors. + system can be used in addition, or as a replacement, for interceptors. </para> <para> - Essentially all of the methods of the <literal>Session</literal> interface correlate - to an event. You have a <literal>LoadEvent</literal>, a <literal>FlushEvent</literal>, etc - (consult the XML configuration-file DTD or the <literal>org.hibernate.event</literal> - package for the full list of defined event types). When a request is made of one of + All the methods of the <literal>Session</literal> interface correlate + to an event. You have a <literal>LoadEvent</literal>, a <literal>FlushEvent</literal>, etc. + Consult the XML configuration-file DTD or the <literal>org.hibernate.event</literal> + package for the full list of defined event types. When a request is made of one of these methods, the Hibernate <literal>Session</literal> generates an appropriate event and passes it to the configured event listeners for that type. Out-of-the-box, these listeners implement the same processing in which those methods always resulted. However, you are free to implement a customization of one of the listener interfaces - (i.e., the <literal>LoadEvent</literal> is processed by the registered implemenation + (i.e., the <literal>LoadEvent</literal> is processed by the registered implementation of the <literal>LoadEventListener</literal> interface), in which case their implementation would be responsible for processing any <literal>load()</literal> requests made of the <literal>Session</literal>. </para> <para> - The listeners should be considered effectively singletons; meaning, they are shared between - requests, and thus should not save any state as instance variables. + The listeners should be considered singletons. This means they are shared between + requests, and should not save any state as instance variables. </para> <para> - A custom listener should implement the appropriate interface for the event it wants to + A custom listener implements the appropriate interface for the event it wants to process and/or extend one of the convenience base classes (or even the default event listeners used by Hibernate out-of-the-box as these are declared non-final for this purpose). Custom listeners can either be registered programmatically through the <literal>Configuration</literal> object, or specified in the Hibernate configuration - XML (declarative configuration through the properties file is not supported). Here's an + XML. Declarative configuration through the properties file is not supported. Here is an example of a custom load event listener: </para> @@ -227,7 +227,7 @@ </hibernate-configuration>]]></programlisting> <para> - Instead, you may register it programmatically: + Instead, you can register it programmatically: </para> <programlisting><![CDATA[Configuration cfg = new Configuration(); @@ -237,13 +237,13 @@ <para> Listeners registered declaratively cannot share instances. If the same class name is used in multiple <literal>&lt;listener/&gt;</literal> elements, each reference will - result in a separate instance of that class. If you need the capability to share + result in a separate instance of that class. If you need to share listener instances between listener types you must use the programmatic registration approach. </para> <para> - Why implement an interface and define the specific type during configuration? Well, a + Why implement an interface and define the specific type during configuration? A listener implementation could implement multiple event listener interfaces. Having the type additionally defined during registration makes it easier to turn custom listeners on or off during configuration. @@ -255,8 +255,8 @@ <title>Hibernate declarative security</title> <para> Usually, declarative security in Hibernate applications is managed in a session facade - layer. Now, Hibernate3 allows certain actions to be permissioned via JACC, and authorized - via JAAS. This is optional functionality built on top of the event architecture. + layer. Hibernate3 allows certain actions to be permissioned via JACC, and authorized + via JAAS. This is an optional functionality that is built on top of the event architecture. </para> <para> @@ -270,13 +270,13 @@ <listener type="pre-load" class="org.hibernate.secure.JACCPreLoadEventListener"/>]]></programlisting> <para> - Note that <literal>&lt;listener type="..." class="..."/&gt;</literal> is just a shorthand + Note that <literal>&lt;listener type="..." class="..."/&gt;</literal> is shorthand for <literal>&lt;event type="..."&gt;&lt;listener class="..."/&gt;&lt;/event&gt;</literal> when there is exactly one listener for a particular event type. </para> <para> - Next, still in <literal>hibernate.cfg.xml</literal>, bind the permissions to roles: + Next, while still in <literal>hibernate.cfg.xml</literal>, bind the permissions to roles: </para> <programlisting><![CDATA[<grant role="admin" entity-name="User" actions="insert,update,read"/> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_mappings.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_mappings.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_mappings.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -27,9 +27,10 @@ <chapter id="example-mappings"> <title>Example: Various Mappings</title> - + + <para> - This chapters shows off some more complex association mappings. + This chapters explores some more complex association mappings. </para> <sect1 id="example-mappings-emp"> @@ -37,8 +38,8 @@ <para> The following model of the relationship between <literal>Employer</literal> and - <literal>Employee</literal> uses an actual entity class (<literal>Employment</literal>) - to represent the association. This is done because there might be more than one + <literal>Employee</literal> uses an entity class (<literal>Employment</literal>) + to represent the association. You can do this when there might be more than one period of employment for the same two parties. Components are used to model monetary values and employee names. </para> @@ -53,7 +54,7 @@ </mediaobject> <para> - Heres a possible mapping document: + Here is a possible mapping document: </para> <programlisting><![CDATA[<hibernate-mapping> @@ -106,7 +107,7 @@ </hibernate-mapping>]]></programlisting> <para> - And heres the table schema generated by <literal>SchemaExport</literal>. + Here is the table schema generated by <literal>SchemaExport</literal>. </para> <programlisting><![CDATA[create table employers ( @@ -150,10 +151,10 @@ <para> Consider the following model of the relationships between <literal>Work</literal>, - <literal>Author</literal> and <literal>Person</literal>. We represent the relationship - between <literal>Work</literal> and <literal>Author</literal> as a many-to-many - association. We choose to represent the relationship between <literal>Author</literal> - and <literal>Person</literal> as one-to-one association. Another possibility would be to + <literal>Author</literal> and <literal>Person</literal>. In the example, the relationship + between <literal>Work</literal> and <literal>Author</literal> is represented as a many-to-many + association and the relationship between <literal>Author</literal> + and <literal>Person</literal> is represented as one-to-one association. Another possibility would be to have <literal>Author</literal> extend <literal>Person</literal>. </para> @@ -223,11 +224,11 @@ </hibernate-mapping>]]></programlisting> <para> - There are four tables in this mapping. <literal>works</literal>, + There are four tables in this mapping: <literal>works</literal>, <literal>authors</literal> and <literal>persons</literal> hold work, author and person data respectively. <literal>author_work</literal> is an association - table linking authors to works. Heres the table schema, as generated by - <literal>SchemaExport</literal>. + table linking authors to works. Here is the table schema, as generated by + <literal>SchemaExport</literal>: </para> <programlisting><![CDATA[create table works ( @@ -271,14 +272,14 @@ <title>Customer/Order/Product</title> <para> - Now consider a model of the relationships between <literal>Customer</literal>, - <literal>Order</literal> and <literal>LineItem</literal> and <literal>Product</literal>. + In this section we consider a model of the relationships between <literal>Customer</literal>, + <literal>Order</literal>, <literal>Line Item</literal> and <literal>Product</literal>. There is a one-to-many association between <literal>Customer</literal> and - <literal>Order</literal>, but how should we represent <literal>Order</literal> / - <literal>LineItem</literal> / <literal>Product</literal>? I've chosen to map - <literal>LineItem</literal> as an association class representing the many-to-many + <literal>Order</literal>, but how can you represent <literal>Order</literal> / + <literal>LineItem</literal> / <literal>Product</literal>? In the example, + <literal>LineItem</literal> is mapped as an association class representing the many-to-many association between <literal>Order</literal> and <literal>Product</literal>. In - Hibernate, this is called a composite element. + Hibernate this is called a composite element. </para> <mediaobject> @@ -291,7 +292,7 @@ </mediaobject> <para> - The mapping document: + The mapping document will look like this: </para> <programlisting><![CDATA[<hibernate-mapping> @@ -379,12 +380,12 @@ <title>Miscellaneous example mappings</title> <para> - These examples are all taken from the Hibernate test suite. You - will find many other useful example mappings there. Look in the + These examples are available from the Hibernate test suite. You + will find many other useful example mappings there by searching in the <literal>test</literal> folder of the Hibernate distribution. </para> - <para>TODO: put words around this stuff</para> + <!-- <<para>TODO: put words around this stuff</para>--> <sect2 id="example-mappings-typed-onetone"> <title>"Typed" one-to-one association</title> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_parentchild.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_parentchild.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_parentchild.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -29,36 +29,36 @@ <title>Example: Parent/Child</title> <para> - One of the very first things that new users try to do with Hibernate is to model a parent / child type - relationship. There are two different approaches to this. For various reasons the most convenient + One of the first things that new users want to do with Hibernate is to model a parent/child type + relationship. There are two different approaches to this. The most convenient approach, especially for new users, is to model both <literal>Parent</literal> and <literal>Child</literal> as entity classes with a <literal>&lt;one-to-many&gt;</literal> association from <literal>Parent</literal> - to <literal>Child</literal>. (The alternative approach is to declare the <literal>Child</literal> as a - <literal>&lt;composite-element&gt;</literal>.) Now, it turns out that default semantics of a one to many - association (in Hibernate) are much less close to the usual semantics of a parent / child relationship than - those of a composite element mapping. We will explain how to use a <emphasis>bidirectional one to many - association with cascades</emphasis> to model a parent / child relationship efficiently and elegantly. - It's not at all difficult! + to <literal>Child</literal>. The alternative approach is to declare the <literal>Child</literal> as a + <literal>&lt;composite-element&gt;</literal>. The default semantics of a one-to-many + association in Hibernate are much less close to the usual semantics of a parent/child relationship than + those of a composite element mapping. We will explain how to use a <emphasis>bidirectional one-to-many + association with cascades</emphasis> to model a parent/child relationship efficiently and elegantly. + </para> <sect1 id="example-parentchild-collections"> <title>A note about collections</title> <para> - Hibernate collections are considered to be a logical part of their owning entity; never of the - contained entities. This is a crucial distinction! It has the following consequences: + Hibernate collections are considered to be a logical part of their owning entity and not of the + contained entities. Be aware that this is a critical distinction that has the following consequences: </para> <itemizedlist> <listitem> <para> - When we remove / add an object from / to a collection, the version number of the collection owner + When you remove/add an object from/to a collection, the version number of the collection owner is incremented. </para> </listitem> <listitem> <para> - If an object that was removed from a collection is an instance of a value type (eg, a composite + If an object that was removed from a collection is an instance of a value type (e.g. a composite element), that object will cease to be persistent and its state will be completely removed from the database. Likewise, adding a value type instance to the collection will cause its state to be immediately persistent. @@ -66,9 +66,9 @@ </listitem> <listitem> <para> - On the other hand, if an entity is removed from a collection (a one-to-many or many-to-many - association), it will not be deleted, by default. This behaviour is completely consistent - a - change to the internal state of another entity should not cause the associated entity to vanish! + Conversely, if an entity is removed from a collection (a one-to-many or many-to-many + association), it will not be deleted by default. This behavior is completely consistent; a + change to the internal state of another entity should not cause the associated entity to vanish. Likewise, adding an entity to a collection does not cause that entity to become persistent, by default. </para> @@ -76,9 +76,9 @@ </itemizedlist> <para> - Instead, the default behaviour is that adding an entity to a collection merely creates a link between - the two entities, while removing it removes the link. This is very appropriate for all sorts of cases. - Where it is not appropriate at all is the case of a parent / child relationship, where the life of the + Adding an entity to a collection, by default, merely creates a link between + the two entities. Removing the entity will remove the link. This is appropriate for all sorts of cases. + However, it is not appropriate in the case of a parent/child relationship. In this case, the life of the child is bound to the life cycle of the parent. </para> @@ -98,7 +98,7 @@ </set>]]></programlisting> <para> - If we were to execute the following code + If we were to execute the following code: </para> <programlisting><![CDATA[Parent p = .....; @@ -125,7 +125,7 @@ <para> This is not only inefficient, but also violates any <literal>NOT NULL</literal> constraint on the - <literal>parent_id</literal> column. We can fix the nullability constraint violation by specifying + <literal>parent_id</literal> column. You can fix the nullability constraint violation by specifying <literal>not-null="true"</literal> in the collection mapping: </para> @@ -138,21 +138,21 @@ However, this is not the recommended solution. </para> <para> - The underlying cause of this behaviour is that the link (the foreign key <literal>parent_id</literal>) + The underlying cause of this behavior is that the link (the foreign key <literal>parent_id</literal>) from <literal>p</literal> to <literal>c</literal> is not considered part of the state of the - <literal>Child</literal> object and is therefore not created in the <literal>INSERT</literal>. So the + <literal>Child</literal> object and is therefore not created in the <literal>INSERT</literal>. The solution is to make the link part of the <literal>Child</literal> mapping. </para> <programlisting><![CDATA[<many-to-one name="parent" column="parent_id" not-null="true"/>]]></programlisting> <para> - (We also need to add the <literal>parent</literal> property to the <literal>Child</literal> class.) + You also need to add the <literal>parent</literal> property to the <literal>Child</literal> class. </para> <para> Now that the <literal>Child</literal> entity is managing the state of the link, we tell the collection - not to update the link. We use the <literal>inverse</literal> attribute. + not to update the link. We use the <literal>inverse</literal> attribute to do this: </para> <programlisting><![CDATA[<set name="children" inverse="true"> @@ -161,7 +161,7 @@ </set>]]></programlisting> <para> - The following code would be used to add a new <literal>Child</literal> + The following code would be used to add a new <literal>Child</literal>: </para> <programlisting><![CDATA[Parent p = (Parent) session.load(Parent.class, pid); @@ -172,11 +172,11 @@ session.flush();]]></programlisting> <para> - And now, only one SQL <literal>INSERT</literal> would be issued! + Only one SQL <literal>INSERT</literal> would now be issued. </para> <para> - To tighten things up a bit, we could create an <literal>addChild()</literal> method of + You could also create an <literal>addChild()</literal> method of <literal>Parent</literal>. </para> @@ -186,7 +186,7 @@ }]]></programlisting> <para> - Now, the code to add a <literal>Child</literal> looks like + The code to add a <literal>Child</literal> looks like this: </para> <programlisting><![CDATA[Parent p = (Parent) session.load(Parent.class, pid); @@ -201,7 +201,7 @@ <title>Cascading life cycle</title> <para> - The explicit call to <literal>save()</literal> is still annoying. We will address this by + You can address the frustrations of the explicit call to <literal>save()</literal> by using cascades. </para> @@ -211,7 +211,7 @@ </set>]]></programlisting> <para> - This simplifies the code above to + This simplifies the code above to: </para> <programlisting><![CDATA[Parent p = (Parent) session.load(Parent.class, pid); @@ -220,7 +220,7 @@ session.flush();]]></programlisting> <para> - Similarly, we don't need to iterate over the children when saving or deleting a <literal>Parent</literal>. + Similarly, we do not need to iterate over the children when saving or deleting a <literal>Parent</literal>. The following removes <literal>p</literal> and all its children from the database. </para> @@ -229,7 +229,7 @@ session.flush();]]></programlisting> <para> - However, this code + However, the following code: </para> <programlisting><![CDATA[Parent p = (Parent) session.load(Parent.class, pid); @@ -239,8 +239,8 @@ session.flush();]]></programlisting> <para> - will not remove <literal>c</literal> from the database; it will ony remove the link to <literal>p</literal> - (and cause a <literal>NOT NULL</literal> constraint violation, in this case). You need to explicitly + will not remove <literal>c</literal> from the database. In this case, it will only remove the link to <literal>p</literal> + and cause a <literal>NOT NULL</literal> constraint violation. You need to explicitly <literal>delete()</literal> the <literal>Child</literal>. </para> @@ -251,8 +251,8 @@ session.flush();]]></programlisting> <para> - Now, in our case, a <literal>Child</literal> can't really exist without its parent. So if we remove - a <literal>Child</literal> from the collection, we really do want it to be deleted. For this, we must + In our case, a <literal>Child</literal> cannot exist without its parent. So if we remove + a <literal>Child</literal> from the collection, we do want it to be deleted. To do this, we must use <literal>cascade="all-delete-orphan"</literal>. </para> @@ -262,8 +262,8 @@ </set>]]></programlisting> <para> - Note: even though the collection mapping specifies <literal>inverse="true"</literal>, cascades are - still processed by iterating the collection elements. So if you require that an object be saved, + Even though the collection mapping specifies <literal>inverse="true"</literal>, cascades are + still processed by iterating the collection elements. If you need an object be saved, deleted or updated by cascade, you must add it to the collection. It is not enough to simply call <literal>setParent()</literal>. </para> @@ -275,10 +275,10 @@ <para> Suppose we loaded up a <literal>Parent</literal> in one <literal>Session</literal>, made some changes - in a UI action and wish to persist these changes in a new session by calling <literal>update()</literal>. - The <literal>Parent</literal> will contain a collection of childen and, since cascading update is enabled, + in a UI action and wanted to persist these changes in a new session by calling <literal>update()</literal>. + The <literal>Parent</literal> will contain a collection of children and, since the cascading update is enabled, Hibernate needs to know which children are newly instantiated and which represent existing rows in the - database. Lets assume that both <literal>Parent</literal> and <literal>Child</literal> have genenerated + database. We will also assume that both <literal>Parent</literal> and <literal>Child</literal> have generated identifier properties of type <literal>Long</literal>. Hibernate will use the identifier and version/timestamp property value to determine which of the children are new. (See <xref linkend="objectstate-saveorupdate"/>.) <emphasis>In Hibernate3, it is no longer necessary to specify @@ -287,7 +287,7 @@ <para> The following code will update <literal>parent</literal> and <literal>child</literal> and insert - <literal>newChild</literal>. + <literal>newChild</literal>: </para> <programlisting><![CDATA[//parent and child were both loaded in a previous session @@ -298,9 +298,9 @@ session.flush();]]></programlisting> <para> - Well, that's all very well for the case of a generated identifier, but what about assigned identifiers - and composite identifiers? This is more difficult, since Hibernate can't use the identifier property to - distinguish between a newly instantiated object (with an identifier assigned by the user) and an + This may be suitable for the case of a generated identifier, but what about assigned identifiers + and composite identifiers? This is more difficult, since Hibernate cannot use the identifier property to + distinguish between a newly instantiated object, with an identifier assigned by the user, and an object loaded in a previous session. In this case, Hibernate will either use the timestamp or version property, or will actually query the second-level cache or, worst case, the database, to see if the row exists. @@ -363,7 +363,7 @@ }]]></programlisting> <para> - Don't worry; in Hibernate3 you don't need to write any of this kind of code if you don't want to. + Do not worry; in Hibernate3 you do not need to write any of this kind of code if you do not want to. </para> --> </sect1> @@ -372,15 +372,15 @@ <title>Conclusion</title> <para> - There is quite a bit to digest here and it might look confusing first time around. However, in practice, - it all works out very nicely. Most Hibernate applications use the parent / child pattern in many places. + The sections we have just covered can be a bit confusing. However, in practice, + it all works out nicely. Most Hibernate applications use the parent/child pattern in many places. </para> <para> We mentioned an alternative in the first paragraph. None of the above issues exist in the case of - <literal>&lt;composite-element&gt;</literal> mappings, which have exactly the semantics of a parent / child - relationship. Unfortunately, there are two big limitations to composite element classes: composite elements - may not own collections, and they should not be the child of any entity other than the unique parent. + <literal>&lt;composite-element&gt;</literal> mappings, which have exactly the semantics of a parent/child + relationship. Unfortunately, there are two big limitations with composite element classes: composite elements + cannot own collections and they should not be the child of any entity other than the unique parent. </para> </sect1> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_weblog.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_weblog.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/example_weblog.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -32,9 +32,9 @@ <title>Persistent Classes</title> <para> - The persistent classes represent a weblog, and an item posted + The persistent classes here represent a weblog and an item posted in a weblog. They are to be modelled as a standard parent/child - relationship, but we will use an ordered bag, instead of a set. + relationship, but we will use an ordered bag, instead of a set: </para> <programlisting><![CDATA[package eg; @@ -116,7 +116,7 @@ <title>Hibernate Mappings</title> <para> - The XML mappings should now be quite straightforward. + The XML mappings are now straightforward. For example: </para> <programlisting><![CDATA[<?xml version="1.0"?> @@ -210,7 +210,7 @@ <para> The following class demonstrates some of the kinds of things - we can do with these classes, using Hibernate. + we can do with these classes using Hibernate: </para> <programlisting><![CDATA[package eg; Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/filters.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/filters.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/filters.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -30,7 +30,7 @@ <para> Hibernate3 provides an innovative new approach to handling data with "visibility" rules. - A <emphasis>Hibernate filter</emphasis> is a global, named, parameterized filter that may be + A <emphasis>Hibernate filter</emphasis> is a global, named, parameterized filter that can be enabled or disabled for a particular Hibernate session. </para> @@ -38,12 +38,12 @@ <title>Hibernate filters</title> <para> - Hibernate3 adds the ability to pre-define filter criteria and attach those filters at both - a class and a collection level. A filter criteria is the ability to define a restriction clause - very similiar to the existing "where" attribute available on the class and various collection - elements. Except these filter conditions can be parameterized. The application can then make - the decision at runtime whether given filters should be enabled and what their parameter - values should be. Filters can be used like database views, but parameterized inside the + Hibernate3 has the ability to pre-define filter criteria and attach those filters at both + a class level and a collection level. A filter criteria allows you to define a restriction clause + similar to the existing "where" attribute available on the class and various collection + elements. These filter conditions, however, can be parameterized. The application can then + decide at runtime whether certain filters should be enabled and what their parameter + values should be. Filters can be used like database views, but they are parameterized inside the application. </para> @@ -58,7 +58,7 @@ </filter-def>]]></programlisting> <para> - Then, this filter can be attached to a class: + This filter can then be attached to a class: </para> <programlisting><![CDATA[<class name="myClass" ...> @@ -67,7 +67,7 @@ </class>]]></programlisting> <para> - or, to a collection: + Or, to a collection: </para> <programlisting><![CDATA[<set ...> @@ -75,26 +75,26 @@ </set>]]></programlisting> <para> - or, even to both (or multiples of each) at the same time. + Or, to both or multiples of each at the same time. </para> <para> The methods on <literal>Session</literal> are: <literal>enableFilter(String filterName)</literal>, <literal>getEnabledFilter(String filterName)</literal>, and <literal>disableFilter(String filterName)</literal>. - By default, filters are <emphasis>not</emphasis> enabled for a given session; they must be explcitly + By default, filters are <emphasis>not</emphasis> enabled for a given session. Filters must be enabled through use of the <literal>Session.enableFilter()</literal> method, which returns an - instance of the <literal>Filter</literal> interface. Using the simple filter defined above, this - would look like: + instance of the <literal>Filter</literal> interface. If you used the simple filter defined above, it would + look like this: </para> <programlisting><![CDATA[session.enableFilter("myFilter").setParameter("myFilterParam", "some-value");]]></programlisting> <para> - Note that methods on the org.hibernate.Filter interface do allow the method-chaining common to much of Hibernate. + Methods on the org.hibernate.Filter interface do allow the method-chaining common to much of Hibernate. </para> <para> - A full example, using temporal data with an effective record date pattern: + The following is a full example, using temporal data with an effective record date pattern: </para> <programlisting><![CDATA[<filter-def name="effectiveDate"> @@ -126,7 +126,7 @@ </class>]]></programlisting> <para> - Then, in order to ensure that you always get back currently effective records, simply + In order to ensure that you are provided with currently effective records, enable the filter on the session prior to retrieving employee data: </para> @@ -138,32 +138,32 @@ ]]></programlisting> <para> - In the HQL above, even though we only explicitly mentioned a salary constraint on the results, - because of the enabled filter the query will return only currently active employees who have - a salary greater than a million dollars. + Even though a salary constraint was mentioned explicitly on the results in the above HQL, + because of the enabled filter, the query will return only currently active employees who have + a salary greater than one million dollars. </para> <para> - Note: if you plan on using filters with outer joining (either through HQL or load fetching) be - careful of the direction of the condition expression. Its safest to set this up for left - outer joining; in general, place the parameter first followed by the column name(s) after + If you want to use filters with outer joining, either through HQL or load fetching, be + careful of the direction of the condition expression. It is safest to set this up for left + outer joining. Place the parameter first followed by the column name(s) after the operator. </para> <para> - After being defined a filter might be attached to multiple entities and/or - collections each with its own condition. That can be tedious when the - conditions are the same each time. Thus <literal>&lt;filter-def/&gt;</literal> - allows defining a default condition, either as an attribute or CDATA: + After being defined, a filter might be attached to multiple entities and/or + collections each with its own condition. This can be problematic when the + conditions are the same each time. Using <literal>&lt;filter-def/&gt;</literal> + allows you to definine a default condition, either as an attribute or CDATA: </para> <programlisting><![CDATA[<filter-def name="myFilter" condition="abc > xyz">...</filter-def> <filter-def name="myOtherFilter">abc=xyz</filter-def>]]></programlisting> <para> - This default condition will then be used whenever the filter is attached to something - without specifying a condition. Note that this means you can give a specific condition - as part of the attachment of the filter which overrides the default condition in that + This default condition will be used whenever the filter is attached to something + without specifying a condition. This means you can give a specific condition + as part of the attachment of the filter that overrides the default condition in that particular case. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/inheritance_mapping.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/inheritance_mapping.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/inheritance_mapping.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -26,10 +26,10 @@ <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> <chapter id="inheritance"> - <title>Inheritance Mapping</title> + <title>Inheritance mapping</title> <sect1 id="inheritance-strategies" revision="3"> - <title>The Three Strategies</title> + <title>The three strategies</title> <para> Hibernate supports the three basic inheritance mapping strategies: @@ -68,25 +68,25 @@ <para> It is possible to use different mapping strategies for different - branches of the same inheritance hierarchy, and then make use of implicit + branches of the same inheritance hierarchy. You can then make use of implicit polymorphism to achieve polymorphism across the whole hierarchy. However, Hibernate does not support mixing <literal>&lt;subclass&gt;</literal>, - and <literal>&lt;joined-subclass&gt;</literal> and + <literal>&lt;joined-subclass&gt;</literal> and <literal>&lt;union-subclass&gt;</literal> mappings under the same root <literal>&lt;class&gt;</literal> element. It is possible to mix together - the table per hierarchy and table per subclass strategies, under the + the table per hierarchy and table per subclass strategies under the the same <literal>&lt;class&gt;</literal> element, by combining the <literal>&lt;subclass&gt;</literal> and <literal>&lt;join&gt;</literal> - elements (see below). + elements (see below for an example). </para> <para> It is possible to define <literal>subclass</literal>, <literal>union-subclass</literal>, - and <literal>joined-subclass</literal> mappings in separate mapping documents, directly beneath - <literal>hibernate-mapping</literal>. This allows you to extend a class hierachy just by adding + and <literal>joined-subclass</literal> mappings in separate mapping documents directly beneath + <literal>hibernate-mapping</literal>. This allows you to extend a class hierarchy by adding a new mapping file. You must specify an <literal>extends</literal> attribute in the subclass mapping, - naming a previously mapped superclass. Note: Previously this feature made the ordering of the mapping - documents important. Since Hibernate3, the ordering of mapping files does not matter when using the + naming a previously mapped superclass. Previously this feature made the ordering of the mapping + documents important. Since Hibernate3, the ordering of mapping files is irrelevant when using the extends keyword. The ordering inside a single mapping file still needs to be defined as superclasses before subclasses. </para> @@ -103,10 +103,10 @@ <title>Table per class hierarchy</title> <para> - Suppose we have an interface <literal>Payment</literal>, with implementors + Suppose we have an interface <literal>Payment</literal> with the implementors <literal>CreditCardPayment</literal>, <literal>CashPayment</literal>, - <literal>ChequePayment</literal>. The table per hierarchy mapping would - look like: + and <literal>ChequePayment</literal>. The table per hierarchy mapping would + display in the following way: </para> <programlisting><![CDATA[<class name="Payment" table="PAYMENT"> @@ -129,9 +129,9 @@ </class>]]></programlisting> <para> - Exactly one table is required. There is one big limitation of this mapping + Exactly one table is required. There is a limitation of this mapping strategy: columns declared by the subclasses, such as <literal>CCTYPE</literal>, - may not have <literal>NOT NULL</literal> constraints. + cannot have <literal>NOT NULL</literal> constraints. </para> </sect2> @@ -140,7 +140,7 @@ <title>Table per subclass</title> <para> - A table per subclass mapping would look like: + A table per subclass mapping looks like this: </para> <programlisting><![CDATA[<class name="Payment" table="PAYMENT"> @@ -166,25 +166,25 @@ <para> Four tables are required. The three subclass tables have primary - key associations to the superclass table (so the relational model - is actually a one-to-one association). + key associations to the superclass table so the relational model + is actually a one-to-one association. </para> </sect2> <sect2 id="inheritance-tablepersubclass-discriminator" revision="2"> - <title>Table per subclass, using a discriminator</title> + <title>Table per subclass: using a discriminator</title> <para> - Note that Hibernate's implementation of table per subclass requires - no discriminator column. Other object/relational mappers use a - different implementation of table per subclass which requires a type + Hibernate's implementation of table per subclass + does not require a discriminator column. Other object/relational mappers use a + different implementation of table per subclass that requires a type discriminator column in the superclass table. The approach taken by - Hibernate is much more difficult to implement but arguably more - correct from a relational point of view. If you would like to use + Hibernate is much more difficult to implement, but arguably more + correct from a relational point of view. If you want to use a discriminator column with the table per subclass strategy, you - may combine the use of <literal>&lt;subclass&gt;</literal> and - <literal>&lt;join&gt;</literal>, as follow: + can combine the use of <literal>&lt;subclass&gt;</literal> and + <literal>&lt;join&gt;</literal>, as follows: </para> <programlisting><![CDATA[<class name="Payment" table="PAYMENT"> @@ -227,8 +227,8 @@ <title>Mixing table per class hierarchy with table per subclass</title> <para> - You may even mix the table per hierarchy and table per subclass strategies - using this approach: + You can even mix the table per hierarchy and table per subclass strategies + using the following approach: </para> <programlisting><![CDATA[<class name="Payment" table="PAYMENT"> @@ -266,8 +266,8 @@ <title>Table per concrete class</title> <para> - There are two ways we could go about mapping the table per concrete class - strategy. The first is to use <literal>&lt;union-subclass&gt;</literal>. + There are two ways we can map the table per concrete class + strategy. First, you can use <literal>&lt;union-subclass&gt;</literal>. </para> <programlisting><![CDATA[<class name="Payment"> @@ -296,23 +296,23 @@ <para> The limitation of this approach is that if a property is mapped on the superclass, the column name must be the same on all subclass tables. - (We might relax this in a future release of Hibernate.) The identity - generator strategy is not allowed in union subclass inheritance, indeed - the primary key seed has to be shared accross all unioned subclasses - of a hierarchy. + The identity generator strategy is not allowed in union subclass inheritance. + The primary key seed has to be shared across all unioned subclasses + of a hierarchy. + </para> <para> If your superclass is abstract, map it with <literal>abstract="true"</literal>. - Of course, if it is not abstract, an additional table (defaults to - <literal>PAYMENT</literal> in the example above) is needed to hold instances + If it is not abstract, an additional table (it defaults to + <literal>PAYMENT</literal> in the example above), is needed to hold instances of the superclass. </para> </sect2> <sect2 id="inheritance-tableperconcreate-polymorphism"> - <title>Table per concrete class, using implicit polymorphism</title> + <title>Table per concrete class using implicit polymorphism</title> <para> An alternative approach is to make use of implicit polymorphism: @@ -343,12 +343,12 @@ </class>]]></programlisting> <para> - Notice that nowhere do we mention the <literal>Payment</literal> interface - explicitly. Also notice that properties of <literal>Payment</literal> are + Notice that the <literal>Payment</literal> interface + is not mentioned explicitly. Also notice that properties of <literal>Payment</literal> are mapped in each of the subclasses. If you want to avoid duplication, consider using XML entities - (e.g. <literal>[ &lt;!ENTITY allproperties SYSTEM "allproperties.xml"&gt; ]</literal> - in the <literal>DOCTYPE</literal> declartion and + (for example, <literal>[ &lt;!ENTITY allproperties SYSTEM "allproperties.xml"&gt; ]</literal> + in the <literal>DOCTYPE</literal> declaration and <literal>&amp;allproperties;</literal> in the mapping). </para> @@ -372,15 +372,15 @@ </sect2> - <sect2 id="inheritace-mixingpolymorphism"> + <sect2 id="inheritance-mixingpolymorphism"> <title>Mixing implicit polymorphism with other inheritance mappings</title> <para> - There is one further thing to notice about this mapping. Since the subclasses - are each mapped in their own <literal>&lt;class&gt;</literal> element (and since + Since the subclasses + are each mapped in their own <literal>&lt;class&gt;</literal> element, and since <literal>Payment</literal> is just an interface), each of the subclasses could - easily be part of another inheritance hierarchy! (And you can still use polymorphic - queries against the <literal>Payment</literal> interface.) + easily be part of another inheritance hierarchy. You can still use polymorphic + queries against the <literal>Payment</literal> interface. </para> <programlisting><![CDATA[<class name="CreditCardPayment" table="CREDIT_PAYMENT"> @@ -412,12 +412,12 @@ </class>]]></programlisting> <para> - Once again, we don't mention <literal>Payment</literal> explicitly. If we - execute a query against the <literal>Payment</literal> interface - for - example, <literal>from Payment</literal> - Hibernate + Once again, <literal>Payment</literal> is not mentioned explicitly. If we + execute a query against the <literal>Payment</literal> interface, for + example <literal>from Payment</literal>, Hibernate automatically returns instances of <literal>CreditCardPayment</literal> (and its subclasses, since they also implement <literal>Payment</literal>), - <literal>CashPayment</literal> and <literal>ChequePayment</literal> but + <literal>CashPayment</literal> and <literal>ChequePayment</literal>, but not instances of <literal>NonelectronicTransaction</literal>. </para> @@ -429,7 +429,7 @@ <title>Limitations</title> <para> - There are certain limitations to the "implicit polymorphism" approach to + There are limitations to the "implicit polymorphism" approach to the table per concrete-class mapping strategy. There are somewhat less restrictive limitations to <literal>&lt;union-subclass&gt;</literal> mappings. Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/performance.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/performance.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/performance.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -32,9 +32,9 @@ <title>Fetching strategies</title> <para> - A <emphasis>fetching strategy</emphasis> is the strategy Hibernate will use for - retrieving associated objects if the application needs to navigate the association. - Fetch strategies may be declared in the O/R mapping metadata, or over-ridden by a + Hibernate uses a <emphasis>fetching strategy</emphasis> to + retrieve associated objects if the application needs to navigate the association. + Fetch strategies can be declared in the O/R mapping metadata, or over-ridden by a particular HQL or <literal>Criteria</literal> query. </para> @@ -45,35 +45,35 @@ <itemizedlist> <listitem> <para> - <emphasis>Join fetching</emphasis> - Hibernate retrieves the + <emphasis>Join fetching</emphasis>: Hibernate retrieves the associated instance or collection in the same <literal>SELECT</literal>, using an <literal>OUTER JOIN</literal>. </para> </listitem> <listitem> <para> - <emphasis>Select fetching</emphasis> - a second <literal>SELECT</literal> + <emphasis>Select fetching</emphasis>: a second <literal>SELECT</literal> is used to retrieve the associated entity or collection. Unless you explicitly disable lazy fetching by specifying <literal>lazy="false"</literal>, - this second select will only be executed when you actually access the + this second select will only be executed when you access the association. </para> </listitem> <listitem> <para> - <emphasis>Subselect fetching</emphasis> - a second <literal>SELECT</literal> + <emphasis>Subselect fetching</emphasis>: a second <literal>SELECT</literal> is used to retrieve the associated collections for all entities retrieved in a previous query or fetch. Unless you explicitly disable lazy fetching by specifying <literal>lazy="false"</literal>, this second select will only be executed when you - actually access the association. + access the association. </para> </listitem> <listitem> <para> - <emphasis>Batch fetching</emphasis> - an optimization strategy - for select fetching - Hibernate retrieves a batch of entity instances - or collections in a single <literal>SELECT</literal>, by specifying - a list of primary keys or foreign keys. + <emphasis>Batch fetching</emphasis>: an optimization strategy + for select fetching. Hibernate retrieves a batch of entity instances + or collections in a single <literal>SELECT</literal> by specifying + a list of primary or foreign keys. </para> </listitem> </itemizedlist> @@ -85,45 +85,45 @@ <itemizedlist> <listitem> <para> - <emphasis>Immediate fetching</emphasis> - an association, collection or - attribute is fetched immediately, when the owner is loaded. + <emphasis>Immediate fetching</emphasis>: an association, collection or + attribute is fetched immediately when the owner is loaded. </para> </listitem> <listitem> <para> - <emphasis>Lazy collection fetching</emphasis> - a collection is fetched - when the application invokes an operation upon that collection. (This - is the default for collections.) + <emphasis>Lazy collection fetching</emphasis>: a collection is fetched + when the application invokes an operation upon that collection. This + is the default for collections. </para> </listitem> <listitem> <para> - <emphasis>"Extra-lazy" collection fetching</emphasis> - individual + <emphasis>"Extra-lazy" collection fetching</emphasis>: individual elements of the collection are accessed from the database as needed. Hibernate tries not to fetch the whole collection into memory unless - absolutely needed (suitable for very large collections) + absolutely needed. It is suitable for large collections. </para> </listitem> <listitem> <para> - <emphasis>Proxy fetching</emphasis> - a single-valued association is + <emphasis>Proxy fetching</emphasis>: a single-valued association is fetched when a method other than the identifier getter is invoked upon the associated object. </para> </listitem> <listitem> <para> - <emphasis>"No-proxy" fetching</emphasis> - a single-valued association is + <emphasis>"No-proxy" fetching</emphasis>: a single-valued association is fetched when the instance variable is accessed. Compared to proxy fetching, - this approach is less lazy (the association is fetched even when only the - identifier is accessed) but more transparent, since no proxy is visible to + this approach is less lazy; the association is fetched even when only the + identifier is accessed. It is also more transparent, since no proxy is visible to the application. This approach requires buildtime bytecode instrumentation and is rarely necessary. </para> </listitem> <listitem> <para> - <emphasis>Lazy attribute fetching</emphasis> - an attribute or single + <emphasis>Lazy attribute fetching</emphasis>: an attribute or single valued association is fetched when the instance variable is accessed. This approach requires buildtime bytecode instrumentation and is rarely necessary. @@ -133,8 +133,8 @@ <para> We have two orthogonal notions here: <emphasis>when</emphasis> is the association - fetched, and <emphasis>how</emphasis> is it fetched (what SQL is used). Don't - confuse them! We use <literal>fetch</literal> to tune performance. We may use + fetched and <emphasis>how</emphasis> is it fetched. It is important that you do not + confuse them. We use <literal>fetch</literal> to tune performance. We can use <literal>lazy</literal> to define a contract for what data is always available in any detached instance of a particular class. </para> @@ -144,19 +144,19 @@ <para> By default, Hibernate3 uses lazy select fetching for collections and lazy proxy - fetching for single-valued associations. These defaults make sense for almost - all associations in almost all applications. + fetching for single-valued associations. These defaults make sense for most + associations in the majority of applications. </para> <para> - <emphasis>Note:</emphasis> if you set + If you set <literal>hibernate.default_batch_fetch_size</literal>, Hibernate will use the - batch fetch optimization for lazy fetching (this optimization may also be enabled - at a more granular level). + batch fetch optimization for lazy fetching. This optimization can also be enabled + at a more granular level. </para> <para> - However, lazy fetching poses one problem that you must be aware of. Access to a + Please be aware that access to a lazy association outside of the context of an open Hibernate session will result in an exception. For example: </para> @@ -177,22 +177,22 @@ Since the permissions collection was not initialized when the <literal>Session</literal> was closed, the collection will not be able to load its state. <emphasis>Hibernate does not support lazy initialization - for detached objects</emphasis>. The fix is to move the code that reads + for detached objects</emphasis>. This can be fixed by moving the code that reads from the collection to just before the transaction is committed. </para> <para> - Alternatively, we could use a non-lazy collection or association, + Alternatively, you can use a non-lazy collection or association, by specifying <literal>lazy="false"</literal> for the association mapping. However, it is intended that lazy initialization be used for almost all collections and associations. If you define too many non-lazy associations - in your object model, Hibernate will end up needing to fetch the entire - database into memory in every transaction! + in your object model, Hibernate will fetch the entire + database into memory in every transaction. </para> <para> - On the other hand, we often want to choose join fetching (which is non-lazy by - nature) instead of select fetching in a particular transaction. We'll now see + On the other hand, you can use join fetching, which is non-lazy by + nature, instead of select fetching in a particular transaction. We will now explain how to customize the fetching strategy. In Hibernate3, the mechanisms for choosing a fetch strategy are identical for single-valued associations and collections. @@ -244,13 +244,13 @@ </itemizedlist> <para> - No matter what fetching strategy you use, the defined non-lazy graph is guaranteed - to be loaded into memory. Note that this might result in several immediate selects + Irrespective of the fetching strategy you use, the defined non-lazy graph is guaranteed + to be loaded into memory. This might, however, result in several immediate selects being used to execute a particular HQL query. </para> <para> - Usually, we don't use the mapping document to customize fetching. Instead, we + Usually, the mapping document is not used to customize fetching. Instead, we keep the default behavior, and override it for a particular transaction, using <literal>left join fetch</literal> in HQL. This tells Hibernate to fetch the association eagerly in the first select, using an outer join. In the @@ -259,9 +259,9 @@ </para> <para> - If you ever feel like you wish you could change the fetching strategy used by - <literal>get()</literal> or <literal>load()</literal>, simply use a - <literal>Criteria</literal> query, for example: + If you want to change the fetching strategy used by + <literal>get()</literal> or <literal>load()</literal>, you can use a + <literal>Criteria</literal> query. For example: </para> <programlisting><![CDATA[User user = (User) session.createCriteria(User.class) @@ -270,11 +270,11 @@ .uniqueResult();]]></programlisting> <para> - (This is Hibernate's equivalent of what some ORM solutions call a "fetch plan".) + This is Hibernate's equivalent of what some ORM solutions call a "fetch plan". </para> <para> - A completely different way to avoid problems with N+1 selects is to use the + A completely different approach to problems with N+1 selects is to use the second-level cache. </para> @@ -288,11 +288,11 @@ of persistent collections. However, a different mechanism is needed for lazy behavior in single-ended associations. The target entity of the association must be proxied. Hibernate implements lazy initializing proxies for persistent objects - using runtime bytecode enhancement (via the excellent CGLIB library). + using runtime bytecode enhancement which is accessed via the CGLIB library. </para> <para> - By default, Hibernate3 generates proxies (at startup) for all persistent classes + At startup, Hibernate3 generates proxies by default for all persistent classes and uses them to enable lazy fetching of <literal>many-to-one</literal> and <literal>one-to-one</literal> associations. </para> @@ -300,13 +300,12 @@ <para> The mapping file may declare an interface to use as the proxy interface for that class, with the <literal>proxy</literal> attribute. By default, Hibernate uses a subclass - of the class. <emphasis>Note that the proxied class must implement a default constructor - with at least package visibility. We recommend this constructor for all persistent classes!</emphasis> + of the class. <emphasis>The proxied class must implement a default constructor + with at least package visibility. This constructor is recommended for all persistent classes</emphasis>. </para> <para> - There are some gotchas to be aware of when extending this approach to polymorphic - classes, eg. + There are potential problems to note when extending this approach to polymorphic classes.For example: </para> <programlisting><![CDATA[<class name="Cat" proxy="Cat"> @@ -329,7 +328,7 @@ }]]></programlisting> <para> - Secondly, it is possible to break proxy <literal>==</literal>. + Secondly, it is possible to break proxy <literal>==</literal>: </para> <programlisting><![CDATA[Cat cat = (Cat) session.load(Cat.class, id); // instantiate a Cat proxy @@ -346,20 +345,22 @@ System.out.println( dc.getWeight() ); // 11.0]]></programlisting> <para> - Third, you may not use a CGLIB proxy for a <literal>final</literal> class or a class + Third, you cannot use a CGLIB proxy for a <literal>final</literal> class or a class with any <literal>final</literal> methods. </para> <para> - Finally, if your persistent object acquires any resources upon instantiation (eg. in + Finally, if your persistent object acquires any resources upon instantiation (e.g. in initializers or default constructor), then those resources will also be acquired by the proxy. The proxy class is an actual subclass of the persistent class. </para> <para> These problems are all due to fundamental limitations in Java's single inheritance model. - If you wish to avoid these problems your persistent classes must each implement an interface - that declares its business methods. You should specify these interfaces in the mapping file. eg. + To avoid these problems your persistent classes must each implement an interface + that declares its business methods. You should specify these interfaces in the mapping file where + <literal>CatImpl</literal> implements the interface <literal>Cat</literal> and <literal>DomesticCatImpl</literal> + implements the interface <literal>DomesticCat</literal>. For example: </para> <programlisting><![CDATA[<class name="CatImpl" proxy="Cat"> @@ -370,36 +371,40 @@ </class>]]></programlisting> <para> - where <literal>CatImpl</literal> implements the interface <literal>Cat</literal> and - <literal>DomesticCatImpl</literal> implements the interface <literal>DomesticCat</literal>. Then - proxies for instances of <literal>Cat</literal> and <literal>DomesticCat</literal> may be returned - by <literal>load()</literal> or <literal>iterate()</literal>. (Note that <literal>list()</literal> - does not usually return proxies.) + Then proxies for instances of <literal>Cat</literal> and <literal>DomesticCat</literal> can be returned + by <literal>load()</literal> or <literal>iterate()</literal>. </para> <programlisting><![CDATA[Cat cat = (Cat) session.load(CatImpl.class, catid); Iterator iter = session.createQuery("from CatImpl as cat where cat.name='fritz'").iterate(); Cat fritz = (Cat) iter.next();]]></programlisting> - <para> + + <note><title>Note</title> + <para> + <literal>list()</literal> does not usually return proxies. + </para> + </note> + + <para> Relationships are also lazily initialized. This means you must declare any properties to be of type <literal>Cat</literal>, not <literal>CatImpl</literal>. </para> <para> - Certain operations do <emphasis>not</emphasis> require proxy initialization + Certain operations do <emphasis>not</emphasis> require proxy initialization: </para> <itemizedlist spacing="compact"> <listitem> <para> - <literal>equals()</literal>, if the persistent class does not override + <literal>equals()</literal>: if the persistent class does not override <literal>equals()</literal> </para> </listitem> <listitem> <para> - <literal>hashCode()</literal>, if the persistent class does not override + <literal>hashCode()</literal>: if the persistent class does not override <literal>hashCode()</literal> </para> </listitem> @@ -417,8 +422,8 @@ <para> By choosing <literal>lazy="no-proxy"</literal> instead of the default - <literal>lazy="proxy"</literal>, we can avoid the problems associated with typecasting. - However, we will require buildtime bytecode instrumentation, and all operations + <literal>lazy="proxy"</literal>, you can avoid problems associated with typecasting. + However, buildtime bytecode instrumentation is required, and all operations will result in immediate proxy initialization. </para> @@ -429,19 +434,19 @@ <para> A <literal>LazyInitializationException</literal> will be thrown by Hibernate if an uninitialized - collection or proxy is accessed outside of the scope of the <literal>Session</literal>, ie. when + collection or proxy is accessed outside of the scope of the <literal>Session</literal>, i.e., when the entity owning the collection or having the reference to the proxy is in the detached state. </para> <para> - Sometimes we need to ensure that a proxy or collection is initialized before closing the - <literal>Session</literal>. Of course, we can alway force initialization by calling + Sometimes a proxy or collection needs to be initialized before closing the + <literal>Session</literal>. You can force initialization by calling <literal>cat.getSex()</literal> or <literal>cat.getKittens().size()</literal>, for example. - But that is confusing to readers of the code and is not convenient for generic code. + However, this can be confusing to readers of the code and it is not convenient for generic code. </para> <para> - The static methods <literal>Hibernate.initialize()</literal> and <literal>Hibernate.isInitialized()</literal> + The static methods <literal>Hibernate.initialize()</literal> and <literal>Hibernate.isInitialized()</literal>, provide the application with a convenient way of working with lazily initialized collections or proxies. <literal>Hibernate.initialize(cat)</literal> will force the initialization of a proxy, <literal>cat</literal>, as long as its <literal>Session</literal> is still open. @@ -450,7 +455,7 @@ </para> <para> - Another option is to keep the <literal>Session</literal> open until all needed + Another option is to keep the <literal>Session</literal> open until all required collections and proxies have been loaded. In some application architectures, particularly where the code that accesses data using Hibernate, and the code that uses it are in different application layers or different physical processes, it @@ -462,7 +467,7 @@ <listitem> <para> In a web-based application, a servlet filter can be used to close the - <literal>Session</literal> only at the very end of a user request, once + <literal>Session</literal> only at the end of a user request, once the rendering of the view is complete (the <emphasis>Open Session in View</emphasis> pattern). Of course, this places heavy demands on the correctness of the exception handling of your application infrastructure. @@ -475,7 +480,7 @@ <listitem> <para> In an application with a separate business tier, the business logic must - "prepare" all collections that will be needed by the web tier before + "prepare" all collections that the web tier needs before returning. This means that the business tier should load all the data and return all the data already initialized to the presentation/web tier that is required for a particular use case. Usually, the application calls @@ -489,18 +494,18 @@ </listitem> <listitem> <para> - You may also attach a previously loaded object to a new <literal>Session</literal> + You can also attach a previously loaded object to a new <literal>Session</literal> with <literal>merge()</literal> or <literal>lock()</literal> before - accessing uninitialized collections (or other proxies). No, Hibernate does not, - and certainly <emphasis>should</emphasis> not do this automatically, since it - would introduce ad hoc transaction semantics! + accessing uninitialized collections or other proxies. Hibernate does not, + and certainly <emphasis>should</emphasis> not, do this automatically since it + would introduce impromptu transaction semantics. </para> </listitem> </itemizedlist> <para> - Sometimes you don't want to initialize a large collection, but still need some - information about it (like its size) or a subset of the data. + Sometimes you do not want to initialize a large collection, but still need some + information about it, like its size, for example, or a subset of the data. </para> <para> @@ -522,29 +527,29 @@ <title>Using batch fetching</title> <para> - Hibernate can make efficient use of batch fetching, that is, Hibernate can load several uninitialized - proxies if one proxy is accessed (or collections. Batch fetching is an optimization of the lazy select - fetching strategy. There are two ways you can tune batch fetching: on the class and the collection level. + Using batch fetching, Hibernate can load several uninitialized + proxies if one proxy is accessed. Batch fetching is an optimization of the lazy select + fetching strategy. There are two ways you can configure batch fetching: on the class level and the collection level. </para> <para> - Batch fetching for classes/entities is easier to understand. Imagine you have the following situation - at runtime: You have 25 <literal>Cat</literal> instances loaded in a <literal>Session</literal>, each + Batch fetching for classes/entities is easier to understand. Consider the following example: + at runtime you have 25 <literal>Cat</literal> instances loaded in a <literal>Session</literal>, and each <literal>Cat</literal> has a reference to its <literal>owner</literal>, a <literal>Person</literal>. The <literal>Person</literal> class is mapped with a proxy, <literal>lazy="true"</literal>. If you now - iterate through all cats and call <literal>getOwner()</literal> on each, Hibernate will by default - execute 25 <literal>SELECT</literal> statements, to retrieve the proxied owners. You can tune this + iterate through all cats and call <literal>getOwner()</literal> on each, Hibernate will, by default, + execute 25 <literal>SELECT</literal> statements to retrieve the proxied owners. You can tune this behavior by specifying a <literal>batch-size</literal> in the mapping of <literal>Person</literal>: </para> <programlisting><![CDATA[<class name="Person" batch-size="10">...</class>]]></programlisting> <para> - Hibernate will now execute only three queries, the pattern is 10, 10, 5. + Hibernate will now execute only three queries: the pattern is 10, 10, 5. </para> <para> - You may also enable batch fetching of collections. For example, if each <literal>Person</literal> has + You can also enable batch fetching of collections. For example, if each <literal>Person</literal> has a lazy collection of <literal>Cat</literal>s, and 10 persons are currently loaded in the <literal>Session</literal>, iterating through all persons will generate 10 <literal>SELECT</literal>s, one for every call to <literal>getCats()</literal>. If you enable batch fetching for the @@ -565,9 +570,9 @@ </para> <para> - Batch fetching of collections is particularly useful if you have a nested tree of items, ie. - the typical bill-of-materials pattern. (Although a <emphasis>nested set</emphasis> or a - <emphasis>materialized path</emphasis> might be a better option for read-mostly trees.) + Batch fetching of collections is particularly useful if you have a nested tree of items, i.e. + the typical bill-of-materials pattern. However, a <emphasis>nested set</emphasis> or a + <emphasis>materialized path</emphasis> might be a better option for read-mostly trees. </para> </sect2> @@ -576,9 +581,9 @@ <title>Using subselect fetching</title> <para> - If one lazy collection or single-valued proxy has to be fetched, Hibernate loads all of + If one lazy collection or single-valued proxy has to be fetched, Hibernate will load all of them, re-running the original query in a subselect. This works in the same way as - batch-fetching, without the piecemeal loading. + batch-fetching but without the piecemeal loading. </para> <!-- TODO: Write more about this --> @@ -591,10 +596,10 @@ <para> Hibernate3 supports the lazy fetching of individual properties. This optimization technique is also known as <emphasis>fetch groups</emphasis>. Please note that this is mostly a - marketing feature, as in practice, optimizing row reads is much more important than - optimization of column reads. However, only loading some properties of a class might - be useful in extreme cases, when legacy tables have hundreds of columns and the data model - can not be improved. + marketing feature; optimizing row reads is much more important than + optimization of column reads. However, only loading some properties of a class could + be useful in extreme cases. For example, when legacy tables have hundreds of columns and the data model + cannot be improved. </para> <para> @@ -612,9 +617,9 @@ </class>]]></programlisting> <para> - Lazy property loading requires buildtime bytecode instrumentation! If your persistent - classes are not enhanced, Hibernate will silently ignore lazy property settings and - fall back to immediate fetching. + Lazy property loading requires buildtime bytecode instrumentation. If your persistent + classes are not enhanced, Hibernate will ignore lazy property settings and + return to immediate fetching. </para> <para> @@ -636,14 +641,14 @@ </target>]]></programlisting> <para> - A different (better?) way to avoid unnecessary column reads, at least for - read-only transactions is to use the projection features of HQL or Criteria + A different way of avoiding unnecessary column reads, at least for + read-only transactions, is to use the projection features of HQL or Criteria queries. This avoids the need for buildtime bytecode processing and is certainly a preferred solution. </para> <para> - You may force the usual eager fetching of properties using <literal>fetch all + You can force the usual eager fetching of properties using <literal>fetch all properties</literal> in HQL. </para> @@ -657,19 +662,19 @@ <para> A Hibernate <literal>Session</literal> is a transaction-level cache of persistent data. It is possible to configure a cluster or JVM-level (<literal>SessionFactory</literal>-level) cache on - a class-by-class and collection-by-collection basis. You may even plug in a clustered cache. Be - careful. Caches are never aware of changes made to the persistent store by another application - (though they may be configured to regularly expire cached data). + a class-by-class and collection-by-collection basis. You can even plug in a clustered cache. Be + aware that caches are not aware of changes made to the persistent store by another application. + They can, however, be configured to regularly expire cached data. </para> <para revision="1"> You have the option to tell Hibernate which caching implementation to use by specifying the name of a class that implements <literal>org.hibernate.cache.CacheProvider</literal> using the property <literal>hibernate.cache.provider_class</literal>. Hibernate - comes bundled with a number of built-in integrations with open-source cache providers - (listed below); additionally, you could implement your own and plug it in as - outlined above. Note that versions prior to 3.2 defaulted to use EhCache as the - default cache provider; that is no longer the case as of 3.2. + is bundled with a number of built-in integrations with the open-source cache providers + that are listed below. You can also implement your own and plug it in as + outlined above. Note that versions prior to 3.2 use EhCache as the default + cache provider. </para> <table frame="topbot" id="cacheproviders" revision="1"> @@ -767,16 +772,16 @@ </callout> <callout arearefs="cache2"> <para> - <literal>region</literal> (optional, defaults to the class or - collection role name) specifies the name of the second level cache + <literal>region</literal> (optional: defaults to the class or + collection role name): specifies the name of the second level cache region </para> </callout> <callout arearefs="cache3"> <para> - <literal>include</literal> (optional, defaults to <literal>all</literal>) - <literal>non-lazy</literal> specifies that properties of the entity mapped - with <literal>lazy="true"</literal> may not be cached when attribute-level + <literal>include</literal> (optional: defaults to <literal>all</literal>) + <literal>non-lazy</literal>: specifies that properties of the entity mapped + with <literal>lazy="true"</literal> cannot be cached when attribute-level lazy fetching is enabled </para> </callout> @@ -784,7 +789,7 @@ </programlistingco> <para> - Alternatively (preferably?), you may specify <literal>&lt;class-cache&gt;</literal> and + Alternatively, you can specify <literal>&lt;class-cache&gt;</literal> and <literal>&lt;collection-cache&gt;</literal> elements in <literal>hibernate.cfg.xml</literal>. </para> @@ -798,9 +803,9 @@ <title>Strategy: read only</title> <para> - If your application needs to read but never modify instances of a persistent class, a - <literal>read-only</literal> cache may be used. This is the simplest and best performing - strategy. It's even perfectly safe for use in a cluster. + If your application needs to read, but not modify, instances of a persistent class, a + <literal>read-only</literal> cache can be used. This is the simplest and optimal performing + strategy. It is even safe for use in a cluster. </para> <programlisting><![CDATA[<class name="eg.Immutable" mutable="false"> @@ -818,11 +823,11 @@ If the application needs to update data, a <literal>read-write</literal> cache might be appropriate. This cache strategy should never be used if serializable transaction isolation level is required. If the cache is used in a JTA environment, you must specify the property - <literal>hibernate.transaction.manager_lookup_class</literal>, naming a strategy for obtaining the + <literal>hibernate.transaction.manager_lookup_class</literal> and naming a strategy for obtaining the JTA <literal>TransactionManager</literal>. In other environments, you should ensure that the transaction is completed when <literal>Session.close()</literal> or <literal>Session.disconnect()</literal> is called. - If you wish to use this strategy in a cluster, you should ensure that the underlying cache implementation - supports locking. The built-in cache providers do <emphasis>not</emphasis>. + If you want to use this strategy in a cluster, you should ensure that the underlying cache implementation + supports locking. The built-in cache providers <emphasis>do not</emphasis> support locking. </para> <programlisting><![CDATA[<class name="eg.Cat" .... > @@ -840,8 +845,8 @@ <title>Strategy: nonstrict read/write</title> <para> - If the application only occasionally needs to update data (ie. if it is extremely unlikely that two - transactions would try to update the same item simultaneously) and strict transaction isolation is + If the application only occasionally needs to update data (i.e. if it is extremely unlikely that two + transactions would try to update the same item simultaneously), and strict transaction isolation is not required, a <literal>nonstrict-read-write</literal> cache might be appropriate. If the cache is used in a JTA environment, you must specify <literal>hibernate.transaction.manager_lookup_class</literal>. In other environments, you should ensure that the transaction is completed when @@ -855,7 +860,7 @@ <para> The <literal>transactional</literal> cache strategy provides support for fully transactional cache - providers such as JBoss TreeCache. Such a cache may only be used in a JTA environment and you must + providers such as JBoss TreeCache. Such a cache can only be used in a JTA environment and you must specify <literal>hibernate.transaction.manager_lookup_class</literal>. </para> @@ -947,16 +952,16 @@ <para> Whenever you pass an object to <literal>save()</literal>, <literal>update()</literal> - or <literal>saveOrUpdate()</literal> and whenever you retrieve an object using + or <literal>saveOrUpdate()</literal>, and whenever you retrieve an object using <literal>load()</literal>, <literal>get()</literal>, <literal>list()</literal>, <literal>iterate()</literal> or <literal>scroll()</literal>, that object is added to the internal cache of the <literal>Session</literal>. </para> <para> When <literal>flush()</literal> is subsequently called, the state of that object will - be synchronized with the database. If you do not want this synchronization to occur or + be synchronized with the database. If you do not want this synchronization to occur, or if you are processing a huge number of objects and need to manage memory efficiently, - the <literal>evict()</literal> method may be used to remove the object and its collections + the <literal>evict()</literal> method can be used to remove the object and its collections from the first-level cache. </para> @@ -973,7 +978,7 @@ </para> <para> - To completely evict all objects from the session cache, call <literal>Session.clear()</literal> + To evict all objects from the session cache, call <literal>Session.clear()</literal> </para> <para> @@ -989,31 +994,31 @@ <para> The <literal>CacheMode</literal> controls how a particular session interacts with the second-level - cache. + cache: </para> <itemizedlist> <listitem> <para> - <literal>CacheMode.NORMAL</literal> - read items from and write items to the second-level cache + <literal>CacheMode.NORMAL</literal>: will read items from and write items to the second-level cache </para> </listitem> <listitem> <para> - <literal>CacheMode.GET</literal> - read items from the second-level cache, but don't write to + <literal>CacheMode.GET</literal>: will read items from the second-level cache. Do not write to the second-level cache except when updating data </para> </listitem> <listitem> <para> - <literal>CacheMode.PUT</literal> - write items to the second-level cache, but don't read from + <literal>CacheMode.PUT</literal>: will write items to the second-level cache. Do not read from the second-level cache </para> </listitem> <listitem> <para> - <literal>CacheMode.REFRESH</literal> - write items to the second-level cache, but don't read from - the second-level cache, bypass the effect of <literal>hibernate.cache.use_minimal_puts</literal>, forcing + <literal>CacheMode.REFRESH</literal>: will write items to the second-level cache. Do not read from + the second-level cache. Bypass the effect of <literal>hibernate.cache.use_minimal_puts</literal> forcing a refresh of the second-level cache for all items read from the database </para> </listitem> @@ -1029,8 +1034,8 @@ .getEntries();]]></programlisting> <para> - You'll need to enable statistics, and, optionally, force Hibernate to keep the cache entries in a - more human-understandable format: + You will need to enable statistics and, optionally, force Hibernate to keep the cache entries in a + more readable format: </para> <programlisting><![CDATA[hibernate.generate_statistics true @@ -1042,31 +1047,31 @@ <title>The Query Cache</title> <para> - Query result sets may also be cached. This is only useful for queries that are run - frequently with the same parameters. To use the query cache you must first enable it: + Query result sets can also be cached. This is only useful for queries that are run + frequently with the same parameters. You will first need to enable the query cache: </para> <programlisting><![CDATA[hibernate.cache.use_query_cache true]]></programlisting> <para> - This setting causes the creation of two new cache regions - one holding cached query + This setting creates two new cache regions: one holding cached query result sets (<literal>org.hibernate.cache.StandardQueryCache</literal>), the other holding timestamps of the most recent updates to queryable tables (<literal>org.hibernate.cache.UpdateTimestampsCache</literal>). Note that the query cache does not cache the state of the actual entities in the result set; it caches - only identifier values and results of value type. So the query cache should always be + only identifier values and results of value type. The query cache should always be used in conjunction with the second-level cache. </para> <para> - Most queries do not benefit from caching, so by default queries are not cached. To + Most queries do not benefit from caching, so by default, queries are not cached. To enable caching, call <literal>Query.setCacheable(true)</literal>. This call allows the query to look for existing cache results or add its results to the cache when it is executed. </para> <para> - If you require fine-grained control over query cache expiration policies, you may + If you require fine-grained control over query cache expiration policies, you can specify a named cache region for a particular query by calling <literal>Query.setCacheRegion()</literal>. </para> @@ -1093,9 +1098,9 @@ <title>Understanding Collection performance</title> <para> - We've already spent quite some time talking about collections. - In this section we will highlight a couple more issues about - how collections behave at runtime. + In the previous sections we have covered collections and their applications. + In this section we explore some more issues in relation to + collections at runtime. </para> <sect2 id="performance-collections-taxonomy"> @@ -1108,10 +1113,10 @@ <para>collections of values</para> </listitem> <listitem> - <para>one to many associations</para> + <para>one-to-many associations</para> </listitem> <listitem> - <para>many to many associations</para> + <para>many-to-many associations</para> </listitem> </itemizedlist> @@ -1137,42 +1142,42 @@ </itemizedlist> <para> - All indexed collections (maps, lists, arrays) have a primary key consisting + All indexed collections (maps, lists, and arrays) have a primary key consisting of the <literal>&lt;key&gt;</literal> and <literal>&lt;index&gt;</literal> - columns. In this case collection updates are usually extremely efficient - - the primary key may be efficiently indexed and a particular row may be efficiently + columns. In this case, collection updates are extremely efficient. + The primary key can be efficiently indexed and a particular row can be efficiently located when Hibernate tries to update or delete it. </para> <para> Sets have a primary key consisting of <literal>&lt;key&gt;</literal> and element - columns. This may be less efficient for some types of collection element, particularly - composite elements or large text or binary fields; the database may not be able to index - a complex primary key as efficiently. On the other hand, for one to many or many to many + columns. This can be less efficient for some types of collection element, particularly + composite elements or large text or binary fields, as the database may not be able to index + a complex primary key as efficiently. However, for one-to-many or many-to-many associations, particularly in the case of synthetic identifiers, it is likely to be just - as efficient. (Side-note: if you want <literal>SchemaExport</literal> to actually create - the primary key of a <literal>&lt;set&gt;</literal> for you, you must declare all columns - as <literal>not-null="true"</literal>.) + as efficient. If you want <literal>SchemaExport</literal> to actually create + the primary key of a <literal>&lt;set&gt;</literal>, you must declare all columns + as <literal>not-null="true"</literal>. </para> <para> <literal>&lt;idbag&gt;</literal> mappings define a surrogate key, so they are - always very efficient to update. In fact, they are the best case. + efficient to update. In fact, they are the best case. </para> <para> - Bags are the worst case. Since a bag permits duplicate element values and has no - index column, no primary key may be defined. Hibernate has no way of distinguishing + Bags are the worst case since they permit duplicate element values and, as they have no + index column, no primary key can be defined. Hibernate has no way of distinguishing between duplicate rows. Hibernate resolves this problem by completely removing - (in a single <literal>DELETE</literal>) and recreating the collection whenever it - changes. This might be very inefficient. + in a single <literal>DELETE</literal> and recreating the collection whenever it + changes. This can be inefficient. </para> <para> - Note that for a one-to-many association, the "primary key" may not be the physical - primary key of the database table - but even in this case, the above classification - is still useful. (It still reflects how Hibernate "locates" individual rows of the - collection.) + For a one-to-many association, the "primary key" may not be the physical + primary key of the database table. Even in this case, the above classification + is still useful. It reflects how Hibernate "locates" individual rows of the + collection. </para> </sect2> @@ -1182,29 +1187,29 @@ <para> From the discussion above, it should be clear that indexed collections - and (usually) sets allow the most efficient operation in terms of adding, + and sets allow the most efficient operation in terms of adding, removing and updating elements. </para> <para> There is, arguably, one more advantage that indexed collections have over sets for - many to many associations or collections of values. Because of the structure of a - <literal>Set</literal>, Hibernate doesn't ever <literal>UPDATE</literal> a row when + many-to-many associations or collections of values. Because of the structure of a + <literal>Set</literal>, Hibernate does not <literal>UPDATE</literal> a row when an element is "changed". Changes to a <literal>Set</literal> always work via - <literal>INSERT</literal> and <literal>DELETE</literal> (of individual rows). Once - again, this consideration does not apply to one to many associations. + <literal>INSERT</literal> and <literal>DELETE</literal> of individual rows. Once + again, this consideration does not apply to one-to-many associations. </para> <para> - After observing that arrays cannot be lazy, we would conclude that lists, maps and + After observing that arrays cannot be lazy, you can conclude that lists, maps and idbags are the most performant (non-inverse) collection types, with sets not far - behind. Sets are expected to be the most common kind of collection in Hibernate + behind. You can expect sets to be the most common kind of collection in Hibernate applications. This is because the "set" semantics are most natural in the relational model. </para> <para> - However, in well-designed Hibernate domain models, we usually see that most collections + However, in well-designed Hibernate domain models, most collections are in fact one-to-many associations with <literal>inverse="true"</literal>. For these associations, the update is handled by the many-to-one end of the association, and so considerations of collection update performance simply do not apply. @@ -1216,13 +1221,13 @@ <title>Bags and lists are the most efficient inverse collections</title> <para> - Just before you ditch bags forever, there is a particular case in which bags (and also lists) - are much more performant than sets. For a collection with <literal>inverse="true"</literal> - (the standard bidirectional one-to-many relationship idiom, for example) we can add elements - to a bag or list without needing to initialize (fetch) the bag elements! This is because + There is a particular case, however, in which bags, and also lists, + are much more performant than sets. For a collection with <literal>inverse="true"</literal>, + the standard bidirectional one-to-many relationship idiom, for example, we can add elements + to a bag or list without needing to initialize (fetch) the bag elements. This is because, unlike a <literal>set</literal>, <literal>Collection.add()</literal> or <literal>Collection.addAll()</literal> must always - return true for a bag or <literal>List</literal> (unlike a <literal>Set</literal>). This can - make the following common code much faster. + return true for a bag or <literal>List</literal>. This can + make the following common code much faster: </para> <programlisting><![CDATA[Parent p = (Parent) sess.load(Parent.class, id); @@ -1237,16 +1242,16 @@ <title>One shot delete</title> <para> - Occasionally, deleting collection elements one by one can be extremely inefficient. Hibernate - isn't completely stupid, so it knows not to do that in the case of an newly-empty collection + Deleting collection elements one by one can sometimes be extremely inefficient. Hibernate + knows not to do that in the case of an newly-empty collection (if you called <literal>list.clear()</literal>, for example). In this case, Hibernate will - issue a single <literal>DELETE</literal> and we are done! + issue a single <literal>DELETE</literal>. </para> <para> - Suppose we add a single element to a collection of size twenty and then remove two elements. + Suppose you added a single element to a collection of size twenty and then remove two elements. Hibernate will issue one <literal>INSERT</literal> statement and two <literal>DELETE</literal> - statements (unless the collection is a bag). This is certainly desirable. + statements, unless the collection is a bag. This is certainly desirable. </para> <para> @@ -1259,25 +1264,25 @@ <para>delete eighteen rows one by one and then insert three rows</para> </listitem> <listitem> - <para>remove the whole collection (in one SQL <literal>DELETE</literal>) and insert - all five current elements (one by one)</para> + <para>remove the whole collection in one SQL <literal>DELETE</literal> and insert + all five current elements one by one</para> </listitem> </itemizedlist> <para> - Hibernate isn't smart enough to know that the second option is probably quicker in this case. - (And it would probably be undesirable for Hibernate to be that smart; such behaviour might - confuse database triggers, etc.) + Hibernate cannot know that the second option is probably quicker. + It would probably be undesirable for Hibernate to be that intuitive as such behavior might + confuse database triggers, etc. </para> <para> - Fortunately, you can force this behaviour (ie. the second strategy) at any time by discarding - (ie. dereferencing) the original collection and returning a newly instantiated collection with - all the current elements. This can be very useful and powerful from time to time. + Fortunately, you can force this behavior (i.e. the second strategy) at any time by discarding + (i.e. dereferencing) the original collection and returning a newly instantiated collection with + all the current elements. </para> <para> - Of course, one-shot-delete does not apply to collections mapped <literal>inverse="true"</literal>. + One-shot-delete does not apply to collections mapped <literal>inverse="true"</literal>. </para> </sect2> @@ -1304,7 +1309,7 @@ <para> Hibernate can also use JMX to publish metrics if you enable the - <literal>StatisticsService</literal> MBean. You may enable a single MBean for all your + <literal>StatisticsService</literal> MBean. You can enable a single MBean for all your <literal>SessionFactory</literal> or one per factory. See the following code for minimalistic configuration examples: </para> @@ -1329,13 +1334,13 @@ StatisticsService stats = new StatisticsService(); // MBean implementation server.registerMBean(stats, on); // Register the MBean on the server]]></programlisting> - <para> - TODO: This doesn't make sense: In the first case, we retrieve and use the MBean directly. In the second one, we must give + <!--<para> + TODO: This does not make sense: In the first case, we retrieve and use the MBean directly. In the second one, we must give the JNDI name in which the session factory is held before using it. Use <literal>hibernateStatsBean.setSessionFactoryJNDIName("my/JNDI/Name")</literal> - </para> + </para>--> <para> - You can (de)activate the monitoring for a <literal>SessionFactory</literal> + You can activate and deactivate the monitoring for a <literal>SessionFactory</literal>: </para> <itemizedlist> <listitem> @@ -1365,8 +1370,8 @@ <title>Metrics</title> <para> - Hibernate provides a number of metrics, from very basic to the specialized information - only relevant in certain scenarios. All available counters are described in the + Hibernate provides a number of metrics, from basic information to more specialized information + that is only relevant in certain scenarios. All available counters are described in the <literal>Statistics</literal> interface API, in three categories: </para> <itemizedlist> @@ -1378,8 +1383,8 @@ </listitem> <listitem> <para> - Metrics related to he entities, collections, queries, and caches as a - whole (aka global metrics), + Metrics related to the entities, collections, queries, and caches as a + whole (aka global metrics). </para> </listitem> <listitem> @@ -1392,9 +1397,9 @@ <para> For example, you can check the cache hit, miss, and put ratio of entities, collections - and queries, and the average time a query needs. Beware that the number of milliseconds - is subject to approximation in Java. Hibernate is tied to the JVM precision, on some - platforms this might even only be accurate to 10 seconds. + and queries, and the average time a query needs. Be aware that the number of milliseconds + is subject to approximation in Java. Hibernate is tied to the JVM precision and on some + platforms this might only be accurate to 10 seconds. </para> <para> @@ -1404,7 +1409,7 @@ refer to the <literal>Statistics</literal>, <literal>EntityStatistics</literal>, <literal>CollectionStatistics</literal>, <literal>SecondLevelCacheStatistics</literal>, and <literal>QueryStatistics</literal> API Javadoc for more information. The following - code shows a simple example: + code is a simple example: </para> <programlisting><![CDATA[Statistics stats = HibernateUtil.sessionFactory.getStatistics(); @@ -1425,8 +1430,8 @@ log.info(Cat.class.getName() + " changed " + changes + "times" );]]></programlisting> <para> - To work on all entities, collections, queries and region caches, you can retrieve - the list of names of entities, collections, queries and region caches with the + You can work on all entities, collections, queries and region caches, by retrieving + the list of names of entities, collections, queries and region caches using the following methods: <literal>getQueries()</literal>, <literal>getEntityNames()</literal>, <literal>getCollectionRoleNames()</literal>, and <literal>getSecondLevelCacheRegionNames()</literal>. Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/persistent_classes.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/persistent_classes.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/persistent_classes.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -32,22 +32,22 @@ Persistent classes are classes in an application that implement the entities of the business problem (e.g. Customer and Order in an E-commerce application). Not all instances of a persistent class are considered to be in the persistent - state - an instance may instead be transient or detached. + state. For example, an instance can instead be transient or detached. </para> <para> Hibernate works best if these classes follow some simple rules, also known as the Plain Old Java Object (POJO) programming model. However, none of these rules are hard requirements. Indeed, Hibernate3 assumes very little about - the nature of your persistent objects. You may express a domain model in other - ways: using trees of <literal>Map</literal> instances, for example. + the nature of your persistent objects. You can express a domain model in other + ways (using trees of <literal>Map</literal> instances, for example). </para> <sect1 id="persistent-classes-pojo"> <title>A simple POJO example</title> <para> - Most Java applications require a persistent class representing felines. + Most Java applications require a persistent class representing felines. For example: </para> <programlisting><![CDATA[package eg; @@ -130,7 +130,7 @@ }]]></programlisting> <para> - There are four main rules to follow here: + The four main rules of persistent classes are explored in more detail in the following sections. </para> @@ -139,8 +139,8 @@ <para> <literal>Cat</literal> has a no-argument constructor. All persistent classes must - have a default constructor (which may be non-public) so that Hibernate can instantiate - them using <literal>Constructor.newInstance()</literal>. We strongly recommend having a + have a default constructor (which can be non-public) so that Hibernate can instantiate + them using <literal>Constructor.newInstance()</literal>. It is recommended that you have a default constructor with at least <emphasis>package</emphasis> visibility for runtime proxy generation in Hibernate. </para> @@ -153,9 +153,9 @@ <literal>Cat</literal> has a property called <literal>id</literal>. This property maps to the primary key column of a database table. The property might have been called anything, and its type might have been any primitive type, any primitive "wrapper" - type, <literal>java.lang.String</literal> or <literal>java.util.Date</literal>. (If - your legacy database table has composite keys, you can even use a user-defined class - with properties of these types - see the section on composite identifiers later.) + type, <literal>java.lang.String</literal> or <literal>java.util.Date</literal>. If + your legacy database table has composite keys, you can use a user-defined class + with properties of these types (see the section on composite identifiers later in the chapter.) </para> <para> @@ -164,7 +164,7 @@ </para> <para> - In fact, some functionality is available only to classes which declare an + In fact, some functionality is available only to classes that declare an identifier property: </para> @@ -188,8 +188,8 @@ </itemizedlist> <para> - We recommend you declare consistently-named identifier properties on persistent - classes. We further recommend that you use a nullable (ie. non-primitive) type. + We recommend that you declare consistently-named identifier properties on persistent + classes and that you use a nullable (i.e., non-primitive) type. </para> </sect2> @@ -202,8 +202,8 @@ </para> <para> You can persist <literal>final</literal> classes that do not implement an interface - with Hibernate, but you won't be able to use proxies for lazy association fetching - - which will limit your options for performance tuning. + with Hibernate. You will not, however, be able to use proxies for lazy association fetching which + will ultimately limit your options for performance tuning. </para> <para> You should also avoid declaring <literal>public final</literal> methods on the @@ -217,12 +217,12 @@ <para> <literal>Cat</literal> declares accessor methods for all its persistent fields. - Many other ORM tools directly persist instance variables. We believe it is + Many other ORM tools directly persist instance variables. It is better to provide an indirection between the relational schema and internal data structures of the class. By default, Hibernate persists JavaBeans style - properties, and recognizes method names of the form <literal>getFoo</literal>, - <literal>isFoo</literal> and <literal>setFoo</literal>. You may switch to direct - field access for particular properties, if needed. + properties and recognizes method names of the form <literal>getFoo</literal>, + <literal>isFoo</literal> and <literal>setFoo</literal>. If required, you can switch to direct + field access for particular properties. </para> <para> @@ -240,7 +240,7 @@ <para> A subclass must also observe the first and second rules. It inherits its - identifier property from the superclass, <literal>Cat</literal>. + identifier property from the superclass, <literal>Cat</literal>. For example: </para> <programlisting><![CDATA[package eg; @@ -262,13 +262,13 @@ <para> You have to override the <literal>equals()</literal> and <literal>hashCode()</literal> - methods if you + methods if you: </para> <itemizedlist spacing="compact"> <listitem> <para> intend to put instances of persistent classes in a <literal>Set</literal> - (the recommended way to represent many-valued associations) + (the recommended way to represent many-valued associations); <emphasis>and</emphasis> </para> </listitem> @@ -281,31 +281,31 @@ <para> Hibernate guarantees equivalence of persistent identity (database row) and Java identity - only inside a particular session scope. So as soon as we mix instances retrieved in - different sessions, we must implement <literal>equals()</literal> and - <literal>hashCode()</literal> if we wish to have meaningful semantics for + only inside a particular session scope. When you mix instances retrieved in + different sessions, you must implement <literal>equals()</literal> and + <literal>hashCode()</literal> if you wish to have meaningful semantics for <literal>Set</literal>s. </para> <para> The most obvious way is to implement <literal>equals()</literal>/<literal>hashCode()</literal> by comparing the identifier value of both objects. If the value is the same, both must - be the same database row, they are therefore equal (if both are added to a <literal>Set</literal>, - we will only have one element in the <literal>Set</literal>). Unfortunately, we can't use that - approach with generated identifiers! Hibernate will only assign identifier values to objects - that are persistent, a newly created instance will not have any identifier value! Furthermore, + be the same database row, because they are equal. If both are added to a <literal>Set</literal>, + you will only have one element in the <literal>Set</literal>). Unfortunately, you cannot use that + approach with generated identifiers. Hibernate will only assign identifier values to objects + that are persistent; a newly created instance will not have any identifier value. Furthermore, if an instance is unsaved and currently in a <literal>Set</literal>, saving it will assign an identifier value to the object. If <literal>equals()</literal> and <literal>hashCode()</literal> are based on the identifier value, the hash code would change, breaking the contract of the - <literal>Set</literal>. See the Hibernate website for a full discussion of this problem. Note - that this is not a Hibernate issue, but normal Java semantics of object identity and equality. + <literal>Set</literal>. See the Hibernate website for a full discussion of this problem. This is not + a Hibernate issue, but normal Java semantics of object identity and equality. </para> <para> - We recommend implementing <literal>equals()</literal> and <literal>hashCode()</literal> + It is recommended that you implement <literal>equals()</literal> and <literal>hashCode()</literal> using <emphasis>Business key equality</emphasis>. Business key equality means that the <literal>equals()</literal> method compares only the properties that form the business - key, a key that would identify our instance in the real world (a + key. It is a key that would identify our instance in the real world (a <emphasis>natural</emphasis> candidate key): </para> @@ -334,7 +334,7 @@ }]]></programlisting> <para> - Note that a business key does not have to be as solid as a database + A business key does not have to be as solid as a database primary key candidate (see <xref linkend="transactions-basics-identity"/>). Immutable or unique properties are usually good candidates for a business key. @@ -345,30 +345,33 @@ <sect1 id="persistent-classes-dynamicmodels"> <title>Dynamic models</title> - <para> - <emphasis>Note that the following features are currently considered + + <note><title>Note</title> +<para> + <emphasis>The following features are currently considered experimental and may change in the near future.</emphasis> - </para> - + + </para> +</note> <para> - Persistent entities don't necessarily have to be represented as POJO classes + Persistent entities do not necessarily have to be represented as POJO classes or as JavaBean objects at runtime. Hibernate also supports dynamic models (using <literal>Map</literal>s of <literal>Map</literal>s at runtime) and the - representation of entities as DOM4J trees. With this approach, you don't + representation of entities as DOM4J trees. With this approach, you do not write persistent classes, only mapping files. </para> <para> - By default, Hibernate works in normal POJO mode. You may set a default entity + By default, Hibernate works in normal POJO mode. You can set a default entity representation mode for a particular <literal>SessionFactory</literal> using the <literal>default_entity_mode</literal> configuration option (see - <xref linkend="configuration-optional-properties"/>. + <xref linkend="configuration-optional-properties"/>). </para> <para> - The following examples demonstrates the representation using <literal>Map</literal>s. - First, in the mapping file, an <literal>entity-name</literal> has to be declared - instead of (or in addition to) a class name: + The following examples demonstrate the representation using <literal>Map</literal>s. + First, in the mapping file an <literal>entity-name</literal> has to be declared + instead of, or in addition to, a class name: </para> <programlisting><![CDATA[<hibernate-mapping> @@ -407,14 +410,14 @@ <para> - Note that even though associations are declared using target class names, - the target type of an associations may also be a dynamic entity instead + Even though associations are declared using target class names, + the target type of associations can also be a dynamic entity instead of a POJO. </para> <para> After setting the default entity mode to <literal>dynamic-map</literal> - for the <literal>SessionFactory</literal>, we can at runtime work with + for the <literal>SessionFactory</literal>, you can, at runtime, work with <literal>Map</literal>s of <literal>Map</literal>s: </para> @@ -441,10 +444,10 @@ s.close();]]></programlisting> <para> - The advantages of a dynamic mapping are quick turnaround time for prototyping + One of the main advantages of dynamic mapping is quick turnaround time for prototyping, without the need for entity class implementation. However, you lose compile-time - type checking and will very likely deal with many exceptions at runtime. Thanks - to the Hibernate mapping, the database schema can easily be normalized and sound, + type checking and will likely deal with many exceptions at runtime. As a result of + the Hibernate mapping, the database schema can easily be normalized and sound, allowing to add a proper domain model implementation on top later on. </para> @@ -472,7 +475,7 @@ <literal>EntityMode</literal> is on the <literal>Session</literal> API, not the <literal>SessionFactory</literal>. That way, the new <literal>Session</literal> shares the underlying JDBC connection, transaction, and other context - information. This means you don't have tocall <literal>flush()</literal> + information. This means you do not have to call <literal>flush()</literal> and <literal>close()</literal> on the secondary <literal>Session</literal>, and also leave the transaction and connection handling to the primary unit of work. </para> @@ -489,13 +492,16 @@ <para> <literal>org.hibernate.tuple.Tuplizer</literal>, and its sub-interfaces, are responsible - for managing a particular representation of a piece of data, given that representation's + for managing a particular representation of a piece of data given that representation's <literal>org.hibernate.EntityMode</literal>. If a given piece of data is thought of as - a data structure, then a tuplizer is the thing which knows how to create such a data structure + a data structure, then a tuplizer is the thing that knows how to create such a data structure and how to extract values from and inject values into such a data structure. For example, - for the POJO entity mode, the correpsonding tuplizer knows how create the POJO through its - constructor and how to access the POJO properties using the defined property accessors. - There are two high-level types of Tuplizers, represented by the + for the POJO entity mode, the corresponding tuplizer knows how create the POJO through its + constructor. It also knows how to access the POJO properties using the defined property accessors. + </para> + + <para> + There are two high-level types of Tuplizers, represented by the <literal>org.hibernate.tuple.entity.EntityTuplizer</literal> and <literal>org.hibernate.tuple.component.ComponentTuplizer</literal> interfaces. <literal>EntityTuplizer</literal>s are responsible for managing the above mentioned contracts in regards to entities, while <literal>ComponentTuplizer</literal>s do the same for @@ -503,11 +509,11 @@ </para> <para> - Users may also plug in their own tuplizers. Perhaps you require that a <literal>java.util.Map</literal> + Users can also plug in their own tuplizers. Perhaps you require that a <literal>java.util.Map</literal> implementation other than <literal>java.util.HashMap</literal> be used while in the - dynamic-map entity-mode; or perhaps you need to define a different proxy generation strategy + dynamic-map entity-mode. Or perhaps you need to define a different proxy generation strategy than the one used by default. Both would be achieved by defining a custom tuplizer - implementation. Tuplizers definitions are attached to the entity or component mapping they + implementation. Tuplizer definitions are attached to the entity or component mapping they are meant to manage. Going back to the example of our customer entity: </para> @@ -545,17 +551,17 @@ return new CustomMap(); } } -}]]></programlisting> +}]]></programlisting>m </sect1> - <sect1 id="persistent-classes-extensions"> - <title>Extentsions</title> + <!--<sect1 id="persistent-classes-extensions"> + <title>Extensions</title> <para> TODO: Document user-extension framework in the property and proxy packages </para> - </sect1> + </sect1>--> </chapter> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/preface.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/preface.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/preface.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -39,12 +39,12 @@ <para> Hibernate not only takes care of the mapping from Java classes to database tables (and from Java data types to SQL data types), but also provides data - query and retrieval facilities and can significantly reduce development time otherwise + query and retrieval facilities. It can also significantly reduce development time otherwise spent with manual data handling in SQL and JDBC. </para> <para> - Hibernates goal is to relieve the developer from 95 percent of common data persistence + Hibernate's goal is to relieve the developer from 95 percent of common data persistence related programming tasks. Hibernate may not be the best solution for data-centric applications that only use stored-procedures to implement the business logic in the database, it is most useful with object-oriented domain models and business logic in @@ -75,8 +75,8 @@ </listitem> <listitem> <para> - Have a look at the <literal>eg/</literal> directory in the Hibernate - distribution, it contains a simple standalone application. Copy your + View the <literal>eg/</literal> directory in the Hibernate + distribution. It contains a simple standalone application. Copy your JDBC driver to the <literal>lib/</literal> directory and edit <literal>etc/hibernate.properties</literal>, specifying correct values for your database. From a command prompt in the distribution directory, @@ -89,7 +89,7 @@ Use this reference documentation as your primary source of information. Consider reading <emphasis>Java Persistence with Hibernate</emphasis> (http://www.manning.com/bauer2) if you need more help with application - design or if you prefer a step-by-step tutorial. Also visit + design, or if you prefer a step-by-step tutorial. Also visit http://caveatemptor.hibernate.org and download the example application for Java Persistence with Hibernate. </para> @@ -116,7 +116,7 @@ <para> If you have questions, use the user forum linked on the Hibernate website. We also - provide a JIRA issue trackings system for bug reports and feature requests. If you + provide a JIRA issue tracking system for bug reports and feature requests. If you are interested in the development of Hibernate, join the developer mailing list. If you are interested in translating this documentation into your language, contact us on the developer mailing list. Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_criteria.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_criteria.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_criteria.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -64,7 +64,7 @@ .list();]]></programlisting> <para> - Restrictions may be grouped logically. + Restrictions can be grouped logically. </para> <programlisting><![CDATA[List cats = sess.createCriteria(Cat.class) @@ -86,8 +86,8 @@ .list();]]></programlisting> <para> - There are quite a range of built-in criterion types (<literal>Restrictions</literal> - subclasses), but one that is especially useful lets you specify SQL directly. + There are a range of built-in criterion types (<literal>Restrictions</literal> + subclasses). One of the most useful allows you to specify SQL directly. </para> <programlisting><![CDATA[List cats = sess.createCriteria(Cat.class) @@ -100,9 +100,9 @@ </para> <para> - An alternative approach to obtaining a criterion is to get it from a + You can also obtain a criterion from a <literal>Property</literal> instance. You can create a <literal>Property</literal> - by calling <literal>Property.forName()</literal>. + by calling <literal>Property.forName()</literal>: </para> <programlisting><![CDATA[ @@ -123,7 +123,7 @@ <title>Ordering the results</title> <para> - You may order the results using <literal>org.hibernate.criterion.Order</literal>. + You can order the results using <literal>org.hibernate.criterion.Order</literal>. </para> <programlisting><![CDATA[List cats = sess.createCriteria(Cat.class) @@ -146,8 +146,8 @@ <title>Associations</title> <para> - You may easily specify constraints upon related entities by navigating - associations using <literal>createCriteria()</literal>. + By navigating + associations using <literal>createCriteria()</literal> you can specify constraints upon related entities: </para> <programlisting><![CDATA[List cats = sess.createCriteria(Cat.class) @@ -157,13 +157,13 @@ .list();]]></programlisting> <para> - note that the second <literal>createCriteria()</literal> returns a new - instance of <literal>Criteria</literal>, which refers to the elements of + The second <literal>createCriteria()</literal> returns a new + instance of <literal>Criteria</literal> that refers to the elements of the <literal>kittens</literal> collection. </para> <para> - The following, alternate form is useful in certain circumstances. + There is also an alternate form that is useful in certain circumstances: </para> <programlisting><![CDATA[List cats = sess.createCriteria(Cat.class) @@ -178,9 +178,9 @@ </para> <para> - Note that the kittens collections held by the <literal>Cat</literal> instances + The kittens collections held by the <literal>Cat</literal> instances returned by the previous two queries are <emphasis>not</emphasis> pre-filtered - by the criteria! If you wish to retrieve just the kittens that match the + by the criteria. If you want to retrieve just the kittens that match the criteria, you must use a <literal>ResultTransformer</literal>. </para> @@ -202,7 +202,7 @@ <title>Dynamic association fetching</title> <para> - You may specify association fetching semantics at runtime using + You can specify association fetching semantics at runtime using <literal>setFetchMode()</literal>. </para> @@ -268,7 +268,7 @@ <title>Projections, aggregation and grouping</title> <para> The class <literal>org.hibernate.criterion.Projections</literal> is a - factory for <literal>Projection</literal> instances. We apply a + factory for <literal>Projection</literal> instances. You can apply a projection to a query by calling <literal>setProjection()</literal>. </para> @@ -293,8 +293,8 @@ </para> <para> - An alias may optionally be assigned to a projection, so that the projected value - may be referred to in restrictions or orderings. Here are two different ways to + An alias can be assigned to a projection so that the projected value + can be referred to in restrictions or orderings. Here are two different ways to do this: </para> @@ -361,8 +361,8 @@ <sect1 id="querycriteria-detachedqueries"> <title>Detached queries and subqueries</title> <para> - The <literal>DetachedCriteria</literal> class lets you create a query outside the scope - of a session, and then later execute it using some arbitrary <literal>Session</literal>. + The <literal>DetachedCriteria</literal> class allows you to create a query outside the scope + of a session and then execute it using an arbitrary <literal>Session</literal>. </para> <programlisting><![CDATA[DetachedCriteria query = DetachedCriteria.forClass(Cat.class) @@ -375,8 +375,8 @@ session.close();]]></programlisting> <para> - A <literal>DetachedCriteria</literal> may also be used to express a subquery. Criterion - instances involving subqueries may be obtained via <literal>Subqueries</literal> or + A <literal>DetachedCriteria</literal> can also be used to express a subquery. Criterion + instances involving subqueries can be obtained via <literal>Subqueries</literal> or <literal>Property</literal>. </para> @@ -393,7 +393,7 @@ .list();]]></programlisting> <para> - Even correlated subqueries are possible: + Correlated subqueries are also possible: </para> <programlisting><![CDATA[DetachedCriteria avgWeightForSex = DetachedCriteria.forClass(Cat.class, "cat2") @@ -413,16 +413,16 @@ <title>Queries by natural identifier</title> <para> - For most queries, including criteria queries, the query cache is not very efficient, - because query cache invalidation occurs too frequently. However, there is one special - kind of query where we can optimize the cache invalidation algorithm: lookups by a + For most queries, including criteria queries, the query cache is not efficient + because query cache invalidation occurs too frequently. However, there is a special + kind of query where you can optimize the cache invalidation algorithm: lookups by a constant natural key. In some applications, this kind of query occurs frequently. The criteria API provides special provision for this use case. </para> <para> - First, you should map the natural key of your entity using - <literal>&lt;natural-id&gt;</literal>, and enable use of the second-level cache. + First, map the natural key of your entity using + <literal>&lt;natural-id&gt;</literal> and enable use of the second-level cache. </para> <programlisting><![CDATA[<class name="User"> @@ -438,16 +438,13 @@ </class>]]></programlisting> <para> - Note that this functionality is not intended for use with entities with + This functionality is not intended for use with entities with <emphasis>mutable</emphasis> natural keys. </para> <para> - Next, enable the Hibernate query cache. - </para> - - <para> - Now, <literal>Restrictions.naturalId()</literal> allows us to make use of + Once you have enabled the Hibernate query cache, + the <literal>Restrictions.naturalId()</literal> allows you to make use of the more efficient cache algorithm. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_hql.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_hql.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_hql.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -29,28 +29,28 @@ <title>HQL: The Hibernate Query Language</title> <para> - Hibernate is equipped with an extremely powerful query language that (quite intentionally) - looks very much like SQL. But don't be fooled by the syntax; HQL is fully object-oriented, - understanding notions like inheritence, polymorphism and association. + Hibernate uses a powerful query language (HQL) that is similar in appearance to + SQL. Compared with SQL, however, HQL is fully object-oriented + and understands notions like inheritance, polymorphism and association. </para> <sect1 id="queryhql-casesensitivity"> <title>Case Sensitivity</title> <para> - Queries are case-insensitive, except for names of Java classes and properties. + With the exception of names of Java classes and properties, queries are case-insensitive. So <literal>SeLeCT</literal> is the same as <literal>sELEct</literal> is the same as - <literal>SELECT</literal> but + <literal>SELECT</literal>, but <literal>org.hibernate.eg.FOO</literal> is not - <literal>org.hibernate.eg.Foo</literal> and + <literal>org.hibernate.eg.Foo</literal>, and <literal>foo.barSet</literal> is not <literal>foo.BARSET</literal>. </para> <para> This manual uses lowercase HQL keywords. Some users find queries with uppercase keywords - more readable, but we find this convention ugly when embedded in Java code. + more readable, but this convention is unsuitable for queries embedded in Java code. </para> </sect1> @@ -65,40 +65,40 @@ <programlisting><![CDATA[from eg.Cat]]></programlisting> <para> - which simply returns all instances of the class <literal>eg.Cat</literal>. - We don't usually need to qualify the class name, since <literal>auto-import</literal> - is the default. So we almost always just write: + This returns all instances of the class <literal>eg.Cat</literal>. + You do not usually need to qualify the class name, since <literal>auto-import</literal> + is the default. For example: </para> <programlisting><![CDATA[from Cat]]></programlisting> <para> - Most of the time, you will need to assign an <emphasis>alias</emphasis>, since - you will want to refer to the <literal>Cat</literal> in other parts of the - query. + + In order to refer to the <literal>Cat</literal> in other parts of the + query, you will need to assign an <emphasis>alias</emphasis>. For example: </para> <programlisting><![CDATA[from Cat as cat]]></programlisting> <para> This query assigns the alias <literal>cat</literal> to <literal>Cat</literal> - instances, so we could use that alias later in the query. The <literal>as</literal> - keyword is optional; we could also write: + instances, so you can use that alias later in the query. The <literal>as</literal> + keyword is optional. You could also write: </para> <programlisting><![CDATA[from Cat cat]]></programlisting> <para> - Multiple classes may appear, resulting in a cartesian product or "cross" join. + Multiple classes can appear, resulting in a cartesian product or "cross" join. </para> <programlisting><![CDATA[from Formula, Parameter]]></programlisting> <programlisting><![CDATA[from Formula as form, Parameter as param]]></programlisting> <para> - It is considered good practice to name query aliases using an initial lowercase, + It is good practice to name query aliases using an initial lowercase as this is consistent with Java naming standards for local variables - (eg. <literal>domesticCat</literal>). + (e.g. <literal>domesticCat</literal>). </para> </sect1> @@ -107,8 +107,8 @@ <title>Associations and joins</title> <para> - We may also assign aliases to associated entities, or even to elements of a - collection of values, using a <literal>join</literal>. + You can also assign aliases to associated entities or to elements of a + collection of values using a <literal>join</literal>. For example: </para> <programlisting><![CDATA[from Cat as cat @@ -120,7 +120,7 @@ <programlisting><![CDATA[from Formula form full join form.parameter param]]></programlisting> <para> - The supported join types are borrowed from ANSI SQL + The supported join types are borrowed from ANSI SQL: </para> <itemizedlist spacing="compact"> @@ -165,8 +165,8 @@ with kitten.bodyWeight > 10.0]]></programlisting> <para> - In addition, a "fetch" join allows associations or collections of values to be - initialized along with their parent objects, using a single select. This is particularly + A "fetch" join allows associations or collections of values to be + initialized along with their parent objects using a single select. This is particularly useful in the case of a collection. It effectively overrides the outer join and lazy declarations of the mapping file for associations and collections. See <xref linkend="performance-fetching"/> for more information. @@ -178,9 +178,9 @@ <para> A fetch join does not usually need to assign an alias, because the associated objects - should not be used in the <literal>where</literal> clause (or any other clause). Also, - the associated objects are not returned directly in the query results. Instead, they may - be accessed via the parent object. The only reason we might need an alias is if we are + should not be used in the <literal>where</literal> clause (or any other clause). + The associated objects are also not returned directly in the query results. Instead, they may + be accessed via the parent object. The only reason you might need an alias is if you are recursively join fetching a further collection: </para> @@ -190,24 +190,24 @@ left join fetch child.kittens]]></programlisting> <para> - Note that the <literal>fetch</literal> construct may not be used in queries called using - <literal>iterate()</literal> (though <literal>scroll()</literal> can be used). Nor should - <literal>fetch</literal> be used together with <literal>setMaxResults()</literal> or - <literal>setFirstResult()</literal> as these operations are based on the result rows, which + The <literal>fetch</literal> construct cannot be used in queries called using + <literal>iterate()</literal> (though <literal>scroll()</literal> can be used). + <literal>Fetch</literal> should be used together with <literal>setMaxResults()</literal> or + <literal>setFirstResult()</literal>, as these operations are based on the result rows which usually contain duplicates for eager collection fetching, hence, the number of rows is not what - you'd expect. - Nor may <literal>fetch</literal> be used together with an ad hoc <literal>with</literal> condition. + you would expect. + <literal>Fetch</literal> should also not be used together with impromptu <literal>with</literal> condition. It is possible to create a cartesian product by join fetching more than one collection in a - query, so take care in this case. Join fetching multiple collection roles also sometimes gives - unexpected results for bag mappings, so be careful about how you formulate your queries in this + query, so take care in this case. Join fetching multiple collection roles can produce + unexpected results for bag mappings, so user discretion is advised when formulating queries in this case. Finally, note that <literal>full join fetch</literal> and <literal>right join fetch</literal> are not meaningful. </para> <para> If you are using property-level lazy fetching (with bytecode instrumentation), it is - possible to force Hibernate to fetch the lazy properties immediately (in the first - query) using <literal>fetch all properties</literal>. + possible to force Hibernate to fetch the lazy properties in the first query immediately + using <literal>fetch all properties</literal>. </para> <programlisting><![CDATA[from Document fetch all properties order by name]]></programlisting> @@ -223,7 +223,7 @@ </para> <para> - The queries shown in the previous section all use the <literal>explicit</literal> form where + The queries shown in the previous section all use the <literal>explicit</literal> form, that is, where the join keyword is explicitly used in the from clause. This is the recommended form. </para> @@ -238,47 +238,50 @@ </sect1> <sect1 id="queryhql-identifier-property"> - <title>Refering to identifier property</title> + <title>Referring to identifier property</title> <para> - There are, generally speaking, 2 ways to refer to an entity's identifier property: + There are 2 ways to refer to an entity's identifier property: </para> <itemizedlist spacing="compact"> <listitem> <para> The special property (lowercase) <literal>id</literal> may be used to reference the identifier - property of an entity <emphasis>provided that entity does not define a non-identifier property + property of an entity <emphasis>provided that the entity does not define a non-identifier property named id</emphasis>. </para> </listitem> <listitem> <para> - If the entity defines a named identifier property, you may use that property name. + If the entity defines a named identifier property, you can use that property name. </para> </listitem> </itemizedlist> <para> - References to composite identifier properties follow the same naming rules. If the + References to composite identifier properties follow the same naming rules. If the entity has a non-identifier property named id, the composite identifier property can only - be referenced by its defined named; otherwise, the special <literal>id</literal> property - can be used to rerference the identifier property. + be referenced by its defined named. Otherwise, the special <literal>id</literal> property + can be used to reference the identifier property. </para> + <important> <para> - Note: this has changed significantly starting in version 3.2.2. In previous versions, - <literal>id</literal> <emphasis>always</emphasis> referred to the identifier property no - matter what its actual name. A ramification of that decision was that non-identifier + Please note that, starting in version 3.2.2, this has changed significantly. In previous versions, + <literal>id</literal> <emphasis>always</emphasis> referred to the identifier property + regardless of its actual name. A ramification of that decision was that non-identifier properties named <literal>id</literal> could never be referenced in Hibernate queries. </para> - </sect1> + </important> + </sect1> + <sect1 id="queryhql-select"> <title>The select clause</title> <para> The <literal>select</literal> clause picks which objects and properties to return in - the query result set. Consider: + the query result set. Consider the following: </para> <programlisting><![CDATA[select mate @@ -287,13 +290,13 @@ <para> The query will select <literal>mate</literal>s of other <literal>Cat</literal>s. - Actually, you may express this query more compactly as: + You can express this query more compactly as: </para> <programlisting><![CDATA[select cat.mate from Cat cat]]></programlisting> <para> - Queries may return properties of any value type including properties of component type: + Queries can return properties of any value type including properties of component type: </para> <programlisting><![CDATA[select cat.name from DomesticCat cat @@ -302,8 +305,8 @@ <programlisting><![CDATA[select cust.name.firstName from Customer as cust]]></programlisting> <para> - Queries may return multiple objects and/or properties as an array of type - <literal>Object[]</literal>, + Queries can return multiple objects and/or properties as an array of type + <literal>Object[]</literal>: </para> <programlisting><![CDATA[select mother, offspr, mate.name @@ -312,7 +315,7 @@ left outer join mother.kittens as offspr]]></programlisting> <para> - or as a <literal>List</literal>, + Or as a <literal>List</literal>: </para> <programlisting><![CDATA[select new list(mother, offspr, mate.name) @@ -321,7 +324,7 @@ left outer join mother.kittens as offspr]]></programlisting> <para> - or as an actual typesafe Java object, + Or - assuming that the class <literal>Family</literal> has an appropriate constructor - as an actual typesafe Java object: </para> <programlisting><![CDATA[select new Family(mother, mate, offspr) @@ -329,14 +332,11 @@ join mother.mate as mate left join mother.kittens as offspr]]></programlisting> + <para> - assuming that the class <literal>Family</literal> has an appropriate constructor. + You can assign aliases to selected expressions using <literal>as</literal>: </para> - <para> - You may assign aliases to selected expressions using <literal>as</literal>: - </para> - <programlisting><![CDATA[select max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n from Cat cat]]></programlisting> @@ -357,7 +357,7 @@ <title>Aggregate functions</title> <para> - HQL queries may even return the results of aggregate functions on properties: + HQL queries can even return the results of aggregate functions on properties: </para> <programlisting><![CDATA[select avg(cat.weight), sum(cat.weight), max(cat.weight), count(cat) @@ -365,7 +365,7 @@ <!-- NO LONGER SUPPORTED <para> - Collections may also appear inside aggregate functions in the <literal>select</literal> + Collections can also appear inside aggregate functions in the <literal>select</literal> clause. </para> @@ -374,7 +374,7 @@ --> <para> - The supported aggregate functions are + The supported aggregate functions are: </para> <itemizedlist spacing="compact"> @@ -396,7 +396,7 @@ </itemizedlist> <para> - You may use arithmetic operators, concatenation, and recognized SQL functions + You can use arithmetic operators, concatenation, and recognized SQL functions in the select clause: </para> @@ -408,7 +408,7 @@ <programlisting><![CDATA[select firstName||' '||initial||' '||upper(lastName) from Person]]></programlisting> <para> - The <literal>distinct</literal> and <literal>all</literal> keywords may be used and + The <literal>distinct</literal> and <literal>all</literal> keywords can be used and have the same semantics as in SQL. </para> @@ -429,7 +429,7 @@ <para> returns instances not only of <literal>Cat</literal>, but also of subclasses like - <literal>DomesticCat</literal>. Hibernate queries may name <emphasis>any</emphasis> Java + <literal>DomesticCat</literal>. Hibernate queries can name <emphasis>any</emphasis> Java class or interface in the <literal>from</literal> clause. The query will return instances of all persistent classes that extend that class or implement the interface. The following query would return all persistent objects: @@ -445,9 +445,9 @@ <programlisting><![CDATA[from Named n, Named m where n.name = m.name]]></programlisting> <para> - Note that these last two queries will require more than one SQL <literal>SELECT</literal>. This + These last two queries will require more than one SQL <literal>SELECT</literal>. This means that the <literal>order by</literal> clause does not correctly order the whole result set. - (It also means you can't call these queries using <literal>Query.scroll()</literal>.) + It also means you cannot call these queries using <literal>Query.scroll()</literal>. </para> </sect1> @@ -456,8 +456,8 @@ <title>The where clause</title> <para> - The <literal>where</literal> clause allows you to narrow the list of instances returned. - If no alias exists, you may refer to properties by name: + The <literal>where</literal> clause allows you to refine the list of instances returned. + If no alias exists, you can refer to properties by name: </para> <programlisting><![CDATA[from Cat where name='Fritz']]></programlisting> @@ -469,38 +469,40 @@ <programlisting><![CDATA[from Cat as cat where cat.name='Fritz']]></programlisting> <para> - returns instances of <literal>Cat</literal> named 'Fritz'. + This returns instances of <literal>Cat</literal> named 'Fritz'. </para> + <para> + The following query: <programlisting><![CDATA[select foo from Foo foo, Bar bar where foo.startDate = bar.date]]></programlisting> <para> - will return all instances of <literal>Foo</literal> for which - there exists an instance of <literal>bar</literal> with a + returns all instances of <literal>Foo</literal> with an + instance of <literal>bar</literal> with a <literal>date</literal> property equal to the <literal>startDate</literal> property of the <literal>Foo</literal>. Compound path expressions make the - <literal>where</literal> clause extremely powerful. Consider: + <literal>where</literal> clause extremely powerful. Consider the following: </para> <programlisting><![CDATA[from Cat cat where cat.mate.name is not null]]></programlisting> <para> - This query translates to an SQL query with a table (inner) join. If you were to write - something like + This query translates to an SQL query with a table (inner) join. For example: + </para> <programlisting><![CDATA[from Foo foo where foo.bar.baz.customer.address.city is not null]]></programlisting> <para> - you would end up with a query that would require four table joins in SQL. + would result in a query that would require four table joins in SQL. </para> <para> - The <literal>=</literal> operator may be used to compare not only properties, but also + The <literal>=</literal> operator can be used to compare not only properties, but also instances: </para> @@ -511,7 +513,7 @@ where cat.mate = mate]]></programlisting> <para> - The special property (lowercase) <literal>id</literal> may be used to reference the + The special property (lowercase) <literal>id</literal> can be used to reference the unique identifier of an object. See <xref linkend="queryhql-identifier-property"/> for more information. </para> @@ -521,14 +523,13 @@ from Cat as cat where cat.mate.id = 69]]></programlisting> <para> - The second query is efficient. No table join is required! + The second query is efficient and does not require a table join. </para> <para> - Properties of composite identifiers may also be used. Suppose <literal>Person</literal> - has a composite identifier consisting of <literal>country</literal> and - <literal>medicareNumber</literal>. Again, see <xref linkend="queryhql-identifier-property"/> - for more information regarding referencing identifier properties. + Properties of composite identifiers can also be used. Consider the following example where <literal>Person</literal> + has composite identifiers consisting of <literal>country</literal> and + <literal>medicareNumber</literal>: </para> <programlisting><![CDATA[from bank.Person person @@ -540,11 +541,16 @@ and account.owner.id.medicareNumber = 123456]]></programlisting> <para> - Once again, the second query requires no table join. + Once again, the second query does not require a table join. </para> - - <para> - Likewise, the special property <literal>class</literal> accesses the discriminator value + + <para> + See <xref linkend="queryhql-identifier-property"/> + for more information regarding referencing identifier properties) + </para> + + <para> + The special property <literal>class</literal> accesses the discriminator value of an instance in the case of polymorphic persistence. A Java class name embedded in the where clause will be translated to its discriminator value. </para> @@ -552,21 +558,21 @@ <programlisting><![CDATA[from Cat cat where cat.class = DomesticCat]]></programlisting> <para> - You may also use components or composite user types, or properties of said - component types. See <xref linkend="queryhql-components"/> for more details. + You can also use components or composite user types, or properties of said + component types. See <xref linkend="queryhql-components"/> for more information. </para> <para> - An "any" type has the special properties <literal>id</literal> and <literal>class</literal>, - allowing us to express a join in the following way (where <literal>AuditLog.item</literal> - is a property mapped with <literal>&lt;any&gt;</literal>). + An "any" type has the special properties <literal>id</literal> and <literal>class</literal> that allows you + to express a join in the following way (where <literal>AuditLog.item</literal> + is a property mapped with <literal>&lt;any&gt;</literal>): </para> <programlisting><![CDATA[from AuditLog log, Payment payment where log.item.class = 'Payment' and log.item.id = payment.id]]></programlisting> <para> - Notice that <literal>log.item.class</literal> and <literal>payment.class</literal> + The <literal>log.item.class</literal> and <literal>payment.class</literal> would refer to the values of completely different database columns in the above query. </para> @@ -576,19 +582,19 @@ <title>Expressions</title> <para> - Expressions allowed in the <literal>where</literal> clause include - most of the kind of things you could write in SQL: + Expressions used in the <literal>where</literal> clause include the following: + </para> <itemizedlist spacing="compact"> <listitem> <para> - mathematical operators <literal>+, -, *, /</literal> + mathematical operators: <literal>+, -, *, /</literal> </para> </listitem> <listitem> <para> - binary comparison operators <literal>=, &gt;=, &lt;=, &lt;&gt;, !=, like</literal> + binary comparison operators: <literal>=, &gt;=, &lt;=, &lt;&gt;, !=, like</literal> </para> </listitem> <listitem> @@ -598,7 +604,7 @@ </listitem> <listitem> <para> - Parentheses <literal>( )</literal>, indicating grouping + Parentheses <literal>( )</literal> that indicates grouping </para> </listitem> <listitem> @@ -627,7 +633,7 @@ </listitem> <listitem> <para> - <literal>current_date()</literal>, <literal>current_time()</literal>, + <literal>current_date()</literal>, <literal>current_time()</literal>, and <literal>current_timestamp()</literal> </para> </listitem> @@ -635,7 +641,7 @@ <para> <literal>second(...)</literal>, <literal>minute(...)</literal>, <literal>hour(...)</literal>, <literal>day(...)</literal>, - <literal>month(...)</literal>, <literal>year(...)</literal>, + <literal>month(...)</literal>, and <literal>year(...)</literal> </para> </listitem> <listitem> @@ -674,13 +680,13 @@ HQL functions that take collection-valued path expressions: <literal>size(), minelement(), maxelement(), minindex(), maxindex()</literal>, along with the special <literal>elements()</literal> and <literal>indices</literal> functions - which may be quantified using <literal>some, all, exists, any, in</literal>. + that can be quantified using <literal>some, all, exists, any, in</literal>. </para> </listitem> <listitem> <para> Any database-supported SQL scalar function like <literal>sign()</literal>, - <literal>trunc()</literal>, <literal>rtrim()</literal>, <literal>sin()</literal> + <literal>trunc()</literal>, <literal>rtrim()</literal>, and <literal>sin()</literal> </para> </listitem> <listitem> @@ -690,7 +696,7 @@ </listitem> <listitem> <para> - named parameters <literal>:name</literal>, <literal>:start_date</literal>, <literal>:x1</literal> + named parameters <literal>:name</literal>, <literal>:start_date</literal>, and <literal>:x1</literal> </para> </listitem> <listitem> @@ -707,7 +713,7 @@ </itemizedlist> <para> - <literal>in</literal> and <literal>between</literal> may be used as follows: + <literal>in</literal> and <literal>between</literal> can be used as follows: </para> <programlisting><![CDATA[from DomesticCat cat where cat.name between 'A' and 'B']]></programlisting> @@ -715,7 +721,7 @@ <programlisting><![CDATA[from DomesticCat cat where cat.name in ( 'Foo', 'Bar', 'Baz' )]]></programlisting> <para> - and the negated forms may be written + The negated forms can be written as follows: </para> <programlisting><![CDATA[from DomesticCat cat where cat.name not between 'A' and 'B']]></programlisting> @@ -723,12 +729,12 @@ <programlisting><![CDATA[from DomesticCat cat where cat.name not in ( 'Foo', 'Bar', 'Baz' )]]></programlisting> <para> - Likewise, <literal>is null</literal> and <literal>is not null</literal> may be used to test + Similarly, <literal>is null</literal> and <literal>is not null</literal> can be used to test for null values. </para> <para> - Booleans may be easily used in expressions by declaring HQL query substitutions in Hibernate + Booleans can be easily used in expressions by declaring HQL query substitutions in Hibernate configuration: </para> @@ -742,7 +748,7 @@ <programlisting><![CDATA[from Cat cat where cat.alive = true]]></programlisting> <para> - You may test the size of a collection with the special property <literal>size</literal>, or + You can test the size of a collection with the special property <literal>size</literal> or the special <literal>size()</literal> function. </para> @@ -751,11 +757,11 @@ <programlisting><![CDATA[from Cat cat where size(cat.kittens) > 0]]></programlisting> <para> - For indexed collections, you may refer to the minimum and maximum indices using + For indexed collections, you can refer to the minimum and maximum indices using <literal>minindex</literal> and <literal>maxindex</literal> functions. Similarly, - you may refer to the minimum and maximum elements of a collection of basic type + you can refer to the minimum and maximum elements of a collection of basic type using the <literal>minelement</literal> and <literal>maxelement</literal> - functions. + functions. For example: </para> <programlisting><![CDATA[from Calendar cal where maxelement(cal.holidays) > current_date]]></programlisting> @@ -767,7 +773,7 @@ <para> The SQL functions <literal>any, some, all, exists, in</literal> are supported when passed the element or index set of a collection (<literal>elements</literal> and <literal>indices</literal> functions) - or the result of a subquery (see below). + or the result of a subquery (see below): </para> <programlisting><![CDATA[select mother from Cat as mother, Cat as kit @@ -785,13 +791,13 @@ <para> Note that these constructs - <literal>size</literal>, <literal>elements</literal>, <literal>indices</literal>, <literal>minindex</literal>, <literal>maxindex</literal>, - <literal>minelement</literal>, <literal>maxelement</literal> - may only be used in + <literal>minelement</literal>, <literal>maxelement</literal> - can only be used in the where clause in Hibernate3. </para> <para> - Elements of indexed collections (arrays, lists, maps) may be referred to by - index (in a where clause only): + Elements of indexed collections (arrays, lists, and maps) can be referred to by + index in a where clause only: </para> <programlisting><![CDATA[from Order order where order.items[0].id = 1234]]></programlisting> @@ -807,14 +813,14 @@ where order.items[ maxindex(order.items) ] = item and order.id = 11]]></programlisting> <para> - The expression inside <literal>[]</literal> may even be an arithmetic expression. + The expression inside <literal>[]</literal> can even be an arithmetic expression: </para> <programlisting><![CDATA[select item from Item item, Order order where order.items[ size(order.items) - 1 ] = item]]></programlisting> <para> - HQL also provides the built-in <literal>index()</literal> function, for elements + HQL also provides the built-in <literal>index()</literal> function for elements of a one-to-many association or collection of values. </para> @@ -823,13 +829,13 @@ where index(item) < 5]]></programlisting> <para> - Scalar SQL functions supported by the underlying database may be used + Scalar SQL functions supported by the underlying database can be used: </para> <programlisting><![CDATA[from DomesticCat cat where upper(cat.name) like 'FRI%']]></programlisting> <para> - If you are not yet convinced by all this, think how much longer and less readable the + Consider how much longer and less readable the following query would be in SQL: </para> @@ -869,7 +875,7 @@ <title>The order by clause</title> <para> - The list returned by a query may be ordered by any property of a returned class or components: + The list returned by a query can be ordered by any property of a returned class or components: </para> <programlisting><![CDATA[from DomesticCat cat @@ -885,7 +891,7 @@ <title>The group by clause</title> <para> - A query that returns aggregate values may be grouped by any property of a returned class or components: + A query that returns aggregate values can be grouped by any property of a returned class or components: </para> <programlisting><![CDATA[select cat.color, sum(cat.weight), count(cat) @@ -907,8 +913,8 @@ <para> SQL functions and aggregate functions are allowed in the <literal>having</literal> - and <literal>order by</literal> clauses, if supported by the underlying database - (eg. not in MySQL). + and <literal>order by</literal> clauses if they are supported by the underlying database + (i.e., not in MySQL). </para> <programlisting><![CDATA[select cat @@ -919,10 +925,10 @@ order by count(kitten) asc, sum(kitten.weight) desc]]></programlisting> <para> - Note that neither the <literal>group by</literal> clause nor the - <literal>order by</literal> clause may contain arithmetic expressions. - Also note that Hibernate currently does not expand a grouped entity, - so you can't write <literal>group by cat</literal> if all properties + Neither the <literal>group by</literal> clause nor the + <literal>order by</literal> clause can contain arithmetic expressions. + Hibernate also does not currently expand a grouped entity, + so you cannot write <literal>group by cat</literal> if all properties of <literal>cat</literal> are non-aggregated. You have to list all non-aggregated properties explicitly. </para> @@ -962,12 +968,12 @@ from Cat as cat]]></programlisting> <para> - Note that HQL subqueries may occur only in the select or where clauses. + Note that HQL subqueries can occur only in the select or where clauses. </para> <para> Note that subqueries can also utilize <literal>row value constructor</literal> syntax. See - <xref linkend="queryhql-tuple"/> for more details. + <xref linkend="queryhql-tuple"/> for more information. </para> </sect1> @@ -977,13 +983,13 @@ <para> Hibernate queries can be quite powerful and complex. In fact, the power of the query language - is one of Hibernate's main selling points. Here are some example queries very similar to queries - that I used on a recent project. Note that most queries you will write are much simpler than these! + is one of Hibernate's main strengths. The following example queries are similar to queries + that have been used on recent projects. Please note that most queries you will write will be much simpler than the following examples. </para> <para> - The following query returns the order id, number of items and total value of the order for all - unpaid orders for a particular customer and given minimum total value, ordering the results by + The following query returns the order id, number of items, the given minimum total value and the total value of the order for all + unpaid orders for a particular customer. The results are ordered by total value. In determining the prices, it uses the current catalog. The resulting SQL query, against the <literal>ORDER</literal>, <literal>ORDER_LINE</literal>, <literal>PRODUCT</literal>, <literal>CATALOG</literal> and <literal>PRICE</literal> tables has four inner joins and an @@ -1053,7 +1059,7 @@ order by status.sortOrder]]></programlisting> <para> - If I would have mapped the <literal>statusChanges</literal> collection as a list, instead of a set, + If the <literal>statusChanges</literal> collection was mapped as a list, instead of a set, the query would have been much simpler to write. </para> @@ -1101,7 +1107,7 @@ <para> HQL now supports <literal>update</literal>, <literal>delete</literal> and <literal>insert ... select ...</literal> statements. - See <xref linkend="batch-direct"/> for details. + See <xref linkend="batch-direct"/> for more information. </para> </sect1> @@ -1109,7 +1115,7 @@ <title>Tips &amp; Tricks</title> <para> - You can count the number of query results without actually returning them: + You can count the number of query results without returning them: </para> <programlisting><![CDATA[( (Integer) session.createQuery("select count(*) from ....").iterate().next() ).intValue()]]></programlisting> @@ -1132,7 +1138,7 @@ <programlisting><![CDATA[from User usr where size(usr.messages) >= 1]]></programlisting> <para> - If your database doesn't support subselects, use the following query: + If your database does not support subselects, use the following query: </para> <programlisting><![CDATA[select usr.id, usr.name @@ -1141,8 +1147,9 @@ group by usr.id, usr.name having count(msg) >= 1]]></programlisting> + <para> - As this solution can't return a <literal>User</literal> with zero messages + As this solution cannot return a <literal>User</literal> with zero messages because of the inner join, the following form is also useful: </para> @@ -1170,7 +1177,7 @@ List page = q.list();]]></programlisting> <para> - Collection elements may be ordered or grouped using a query filter: + Collection elements can be ordered or grouped using a query filter: </para> <programlisting><![CDATA[Collection orderedCollection = s.filter( collection, "order by this.amount" ); @@ -1188,8 +1195,8 @@ <title>Components</title> <para> - Components might be used in just about every way that simple value types can be used in HQL - queries. They can appear in the <literal>select</literal> clause: + Components can be used similarly to the simple value types that are used in HQL + queries. They can appear in the <literal>select</literal> clause as follows: </para> <programlisting><![CDATA[select p.name from Person p]]></programlisting> @@ -1219,16 +1226,16 @@ <title>Row value constructor syntax</title> <para> - HQL supports the use of ANSI SQL <literal>row value constructor</literal> syntax (sometimes - called <literal>tuple</literal> syntax), even though the underlying database may not support - that notion. Here we are generally referring to multi-valued comparisons, typically associated + HQL supports the use of ANSI SQL <literal>row value constructor</literal> syntax, sometimes + referred to AS <literal>tuple</literal> syntax, even though the underlying database may not support + that notion. Here, we are generally referring to multi-valued comparisons, typically associated with components. Consider an entity Person which defines a name component: </para> <programlisting><![CDATA[from Person p where p.name.first='John' and p.name.last='Jingleheimer-Schmidt']]></programlisting> <para> - That's valid syntax, although a little verbose. It be nice to make this a bit more concise and use + That is valid syntax although it is a little verbose. You can make this more concise by using <literal>row value constructor</literal> syntax: </para> @@ -1241,8 +1248,8 @@ <programlisting><![CDATA[select p.name from Person p]]></programlisting> <para> - Another time using <literal>row value constructor</literal> syntax can be beneficial - is when using subqueries needing to compare against multiple values: + Using <literal>row value constructor</literal> syntax can also be beneficial + when using subqueries that need to compare against multiple values: </para> <programlisting><![CDATA[from Cat as cat @@ -1251,7 +1258,7 @@ )]]></programlisting> <para> - One thing to consider when deciding if you want to use this syntax is that the query will + One thing to consider when deciding if you want to use this syntax, is that the query will be dependent upon the ordering of the component sub-properties in the metadata. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_sql.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_sql.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/query_sql.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -28,21 +28,21 @@ <chapter id="querysql" revision="2"> <title>Native SQL</title> - <para>You may also express queries in the native SQL dialect of your - database. This is useful if you want to utilize database specific features + <para>You can also express queries in the native SQL dialect of your + database. This is useful if you want to utilize database-specific features such as query hints or the <literal>CONNECT</literal> keyword in Oracle. It also provides a clean migration path from a direct SQL/JDBC based application to Hibernate.</para> - <para>Hibernate3 allows you to specify handwritten SQL (including stored - procedures) for all create, update, delete, and load operations.</para> + <para>Hibernate3 allows you to specify handwritten SQL, including stored + procedures, for all create, update, delete, and load operations.</para> <sect1 id="querysql-creating" revision="4"> <title>Using a <literal>SQLQuery</literal></title> <para>Execution of native SQL queries is controlled via the <literal>SQLQuery</literal> interface, which is obtained by calling - <literal>Session.createSQLQuery()</literal>. The following describes how + <literal>Session.createSQLQuery()</literal>. The following sections describe how to use this API for querying.</para> <sect2> @@ -55,14 +55,14 @@ sess.createSQLQuery("SELECT ID, NAME, BIRTHDATE FROM CATS").list(); ]]></programlisting> - <para>These will both return a List of Object arrays (Object[]) with + <para>These will return a List of Object arrays (Object[]) with scalar values for each column in the CATS table. Hibernate will use ResultSetMetadata to deduce the actual order and types of the returned scalar values.</para> <para>To avoid the overhead of using - <literal>ResultSetMetadata</literal> or simply to be more explicit in - what is returned one can use <literal>addScalar()</literal>.</para> + <literal>ResultSetMetadata</literal>, or simply to be more explicit in + what is returned, one can use <literal>addScalar()</literal>:</para> <programlisting><![CDATA[sess.createSQLQuery("SELECT * FROM CATS") .addScalar("ID", Hibernate.LONG) @@ -82,7 +82,7 @@ </listitem> </itemizedlist> - <para>This will still return Object arrays, but now it will not use + <para>This will return Object arrays, but now it will not use <literal>ResultSetMetadata</literal> but will instead explicitly get the ID, NAME and BIRTHDATE column as respectively a Long, String and a Short from the underlying resultset. This also means that only these three @@ -100,12 +100,12 @@ ]]></programlisting> <para>This is essentially the same query as before, but now - <literal>ResultSetMetaData</literal> is used to decide the type of NAME - and BIRTHDATE where as the type of ID is explicitly specified.</para> + <literal>ResultSetMetaData</literal> is used to determine the type of NAME + and BIRTHDATE, where as the type of ID is explicitly specified.</para> <para>How the java.sql.Types returned from ResultSetMetaData is mapped to Hibernate types is controlled by the Dialect. If a specific type is - not mapped or does not result in the expected type it is possible to + not mapped, or does not result in the expected type, it is possible to customize it via calls to <literal>registerHibernateType</literal> in the Dialect.</para> </sect2> @@ -165,9 +165,9 @@ .addJoin("cat.dog"); ]]></programlisting> - <para>In this example the returned <literal>Cat</literal>'s will have + <para>In this example, the returned <literal>Cat</literal>'s will have their <literal>dog</literal> property fully initialized without any - extra roundtrip to the database. Notice that we added a alias name + extra roundtrip to the database. Notice that you added an alias name ("cat") to be able to specify the target property path of the join. It is possible to do the same eager joining for collections, e.g. if the <literal>Cat</literal> had a one-to-many to <literal>Dog</literal> @@ -179,8 +179,8 @@ ]]></programlisting> <para> - At this stage we are reaching the limits of what is possible with native queries without starting to - enhance the sql queries to make them usable in Hibernate; the problems starts to arise when returning + At this stage you are reaching the limits of what is possible with native queries, without starting to + enhance the sql queries to make them usable in Hibernate. Problems can arise when returning multiple entities of the same type or when the default alias/column names are not enough. </para> </sect2> @@ -188,10 +188,10 @@ <sect2> <title>Returning multiple entities</title> - <para>Until now the result set column names are assumed to be the same + <para>Until now, the result set column names are assumed to be the same as the column names specified in the mapping document. This can be - problematic for SQL queries which join multiple tables, since the same - column names may appear in more than one table.</para> + problematic for SQL queries that join multiple tables, since the same + column names can appear in more than one table.</para> <para>Column alias injection is needed in the following query (which most likely will fail):</para> @@ -201,13 +201,17 @@ .addEntity("mother", Cat.class) ]]></programlisting> - <para>The intention for this query is to return two Cat instances per - row, a cat and its mother. This will fail since there is a conflict of - names since they are mapped to the same column names and on some - databases the returned column aliases will most likely be on the form - "c.ID", "c.NAME", etc. which are not equal to the columns specified in - the mappings ("ID" and "NAME").</para> + + <para> + The query was intended to return two Cat instances per + row: a cat and its mother. The query will, however, fail because there is a conflict of + names; the instances are mapped to the same column names. Also, on some + databases the returned column aliases will most likely be on the form + "c.ID", "c.NAME", etc. which are not equal to the columns specified in + the mappings ("ID" and "NAME"). + </para> + <para>The following form is not vulnerable to column name duplication:</para> @@ -230,13 +234,13 @@ </itemizedlist> <para>The {cat.*} and {mother.*} notation used above is a shorthand for - "all properties". Alternatively, you may list the columns explicitly, but - even in this case we let Hibernate inject the SQL column aliases for + "all properties". Alternatively, you can list the columns explicitly, but + even in this case Hibernate injects the SQL column aliases for each property. The placeholder for a column alias is just the property - name qualified by the table alias. In the following example, we retrieve + name qualified by the table alias. In the following example, you retrieve Cats and their mothers from a different table (cat_log) to the one - declared in the mapping metadata. Notice that we may even use the - property aliases in the where clause if we like.</para> + declared in the mapping metadata. You can even use the + property aliases in the where clause.</para> <programlisting><![CDATA[String sql = "SELECT ID as {c.id}, NAME as {c.name}, " + "BIRTHDATE as {c.birthDate}, MOTHER_ID as {c.mother}, {mother.*} " + @@ -250,13 +254,13 @@ <sect3 id="querysql-aliasreferences" revision="2"> <title>Alias and property references</title> - <para>For most cases the above alias injection is needed, but for - queries relating to more complex mappings like composite properties, - inheritance discriminators, collections etc. there are some specific - aliases to use to allow Hibernate to inject the proper aliases.</para> + <para>In most cases the above alias injection is needed. For + queries relating to more complex mappings, like composite properties, + inheritance discriminators, collections etc., you can use specific + aliases that allow Hibernate to inject the proper aliases.</para> - <para>The following table shows the different possibilities of using - the alias injection. Note: the alias names in the result are examples, + <para>The following table shows the different ways you can use + the alias injection. Please note that the alias names in the result are simply examples; each alias will have a unique and probably different name when used.</para> @@ -339,7 +343,7 @@ </row> <row> - <entry>roperty of the element in the collection</entry> + <entry>property of the element in the collection</entry> <entry><literal>{[aliasname].element.[propertyname]}</literal></entry> @@ -370,7 +374,7 @@ <sect2> <title>Returning non-managed entities</title> - <para>It is possible to apply a ResultTransformer to native sql queries. Allowing it to e.g. return non-managed entities.</para> + <para>It is possible to apply a ResultTransformer to native SQL queries, allowing it to return non-managed entities.</para> <programlisting><![CDATA[sess.createSQLQuery("SELECT NAME, BIRTHDATE FROM CATS") .setResultTransformer(Transformers.aliasToBean(CatDTO.class))]]></programlisting> @@ -396,15 +400,15 @@ <sect2> <title>Handling inheritance</title> - <para>Native sql queries which query for entities that is mapped as part + <para>Native SQL queries which query for entities that are mapped as part of an inheritance must include all properties for the baseclass and all - it subclasses.</para> + its subclasses.</para> </sect2> <sect2> <title>Parameters</title> - <para>Native sql queries support positional as well as named + <para>Native SQL queries support positional as well as named parameters:</para> <programlisting><![CDATA[Query query = sess.createSQLQuery("SELECT * FROM CATS WHERE NAME like ?").addEntity(Cat.class); @@ -421,8 +425,8 @@ <sect1 id="querysql-namedqueries" revision="3"> <title>Named SQL queries</title> - <para>Named SQL queries may be defined in the mapping document and called - in exactly the same way as a named HQL query. In this case, we do + <para>Named SQL queries can be defined in the mapping document and called + in exactly the same way as a named HQL query. In this case, you do <emphasis>not</emphasis> need to call <literal>addEntity()</literal>.</para> @@ -440,10 +444,9 @@ .setMaxResults(50) .list();]]></programlisting> - <para>The <literal>&lt;return-join&gt;</literal> and - <literal>&lt;load-collection&gt;</literal> elements are used to join - associations and define queries which initialize collections, - respectively.</para> + <para>The <literal>&lt;return-join&gt;</literal> element is use to join associations and + the <literal>&lt;load-collection&gt;</literal> element is used to define queries which initialize collections, + </para> <programlisting><![CDATA[<sql-query name="personsWith"> <return alias="person" class="eg.Person"/> @@ -473,8 +476,8 @@ FROM PERSON p WHERE p.NAME LIKE 'Hiber%' </sql-query>]]></programlisting> - <para>You can externalize the resultset mapping informations in a - <literal>&lt;resultset&gt;</literal> element to either reuse them across + <para>You can externalize the resultset mapping information in a + <literal>&lt;resultset&gt;</literal> element which will allow you to either reuse them across several named queries or through the <literal>setResultSetMapping()</literal> API.</para> @@ -497,7 +500,7 @@ WHERE person.NAME LIKE :namePattern </sql-query>]]></programlisting> - <para>You can alternatively use the resultset mapping information in your + <para>You can, alternatively, use the resultset mapping information in your hbm files directly in java code.</para> <programlisting><![CDATA[List cats = sess.createSQLQuery( @@ -510,10 +513,10 @@ <title>Using return-property to explicitly specify column/alias names</title> - <para>With <literal>&lt;return-property&gt;</literal> you can explicitly - tell Hibernate what column aliases to use, instead of using the + <para>You can explicitly + tell Hibernate what column aliases to use with <literal>&lt;return-property&gt;</literal>, instead of using the <literal>{}</literal>-syntax to let Hibernate inject its own - aliases.</para> + aliases.For example:</para> <programlisting><![CDATA[<sql-query name="mySqlQuery"> <return alias="person" class="eg.Person"> @@ -530,7 +533,7 @@ <para><literal>&lt;return-property&gt;</literal> also works with multiple columns. This solves a limitation with the - <literal>{}</literal>-syntax which can not allow fine grained control of + <literal>{}</literal>-syntax which cannot allow fine grained control of multi-column properties.</para> <programlisting><![CDATA[<sql-query name="organizationCurrentEmployments"> @@ -549,9 +552,9 @@ ORDER BY STARTDATE ASC </sql-query>]]></programlisting> - <para>Notice that in this example we used - <literal>&lt;return-property&gt;</literal> in combination with the - <literal>{}</literal>-syntax for injection. Allowing users to choose how + <para>In this example + <literal>&lt;return-property&gt;</literal> was used in combination with the + <literal>{}</literal>-syntax for injection. This allows users to choose how they want to refer column and properties.</para> <para>If your mapping has a discriminator you must use @@ -562,7 +565,7 @@ <sect2 id="sp_query" revision="1"> <title>Using stored procedures for querying</title> - <para>Hibernate 3 introduces support for queries via stored procedures + <para>Hibernate3 provides support for queries via stored procedures and functions. Most of the following documentation is equivalent for both. The stored procedure/function must return a resultset as the first out-parameter to be able to work with Hibernate. An example of such a @@ -600,24 +603,24 @@ { ? = call selectAllEmployments() } </sql-query>]]></programlisting> - <para>Notice stored procedures currently only return scalars and + <para>Stored procedures currently only return scalars and entities. <literal>&lt;return-join&gt;</literal> and <literal>&lt;load-collection&gt;</literal> are not supported.</para> <sect3 id="querysql-limits-storedprocedures" revision="1"> <title>Rules/limitations for using stored procedures</title> - <para>To use stored procedures with Hibernate the procedures/functions - have to follow some rules. If they do not follow those rules they are + <para>You cannot use stored procedures with Hibernate unless you follow some procedure/function + rules. If they do not follow those rules they are not usable with Hibernate. If you still want to use these procedures you have to execute them via <literal>session.connection()</literal>. The rules are different for each database, since database vendors have different stored procedure semantics/syntax.</para> - <para>Stored procedure queries can't be paged with + <para>Stored procedure queries cannot be paged with <literal>setFirstResult()/setMaxResults()</literal>.</para> - <para>Recommended call form is standard SQL92: <literal>{ ? = call + <para>The recommended call form is standard SQL92: <literal>{ ? = call functionName(&lt;parameters&gt;) }</literal> or <literal>{ ? = call procedureName(&lt;parameters&gt;}</literal>. Native call syntax is not supported.</para> @@ -630,8 +633,8 @@ a procedure must be an <literal>OUT</literal> that returns a result set. This is done by using a <literal>SYS_REFCURSOR</literal> type in Oracle 9 or 10. In Oracle - you need to define a <literal>REF CURSOR</literal> type, see - Oracle literature.</para> + you need to define a <literal>REF CURSOR</literal> type. See + Oracle literature for further information.</para> </listitem> </itemizedlist> @@ -640,7 +643,7 @@ <itemizedlist spacing="compact"> <listitem> <para>The procedure must return a result set. Note that since - these servers can/will return multiple result sets and update + these servers can return multiple result sets and update counts, Hibernate will iterate the results and take the first result that is a result set as its return value. Everything else will be discarded.</para> @@ -677,8 +680,8 @@ <sql-delete>DELETE FROM PERSON WHERE ID=?</sql-delete> </class>]]></programlisting> - <para>The SQL is directly executed in your database, so you are free to - use any dialect you like. This will of course reduce the portability of + <para>The SQL is directly executed in your database, so you can + use any dialect you like. This will reduce the portability of your mapping if you use database specific SQL.</para> <para>Stored procedures are supported if the <literal>callable</literal> @@ -694,18 +697,18 @@ <sql-update callable="true">{? = call updatePerson (?, ?)}</sql-update> </class>]]></programlisting> - <para>The order of the positional parameters are currently vital, as they + <para>The order of the positional parameters is vital, as they must be in the same sequence as Hibernate expects them.</para> - <para>You can see the expected order by enabling debug logging for the + <para>You can view the expected order by enabling debug logging for the <literal>org.hibernate.persister.entity</literal> level. With this level - enabled Hibernate will print out the static SQL that is used to create, - update, delete etc. entities. (To see the expected sequence, remember to - not include your custom SQL in the mapping files as that will override the - Hibernate generated static sql.)</para> + enabled, Hibernate will print out the static SQL that is used to create, + update, delete etc. entities. To view the expected sequence, do + not include your custom SQL in the mapping files, as this will override the + Hibernate generated static SQL.</para> - <para>The stored procedures are in most cases (read: better do it than - not) required to return the number of rows inserted/updated/deleted, as + <para>The stored procedures are in most cases + required to return the number of rows inserted, updated and deleted, as Hibernate has some runtime checks for the success of the statement. Hibernate always registers the first statement parameter as a numeric output parameter for the CUD operations:</para> @@ -728,7 +731,7 @@ <sect1 id="querysql-load"> <title>Custom SQL for loading</title> - <para>You may also declare your own SQL (or HQL) queries for entity + <para>You can also declare your own SQL (or HQL) queries for entity loading:</para> <programlisting><![CDATA[<sql-query name="person"> @@ -740,7 +743,7 @@ </sql-query>]]></programlisting> <para>This is just a named query declaration, as discussed earlier. You - may reference this named query in a class mapping:</para> + can reference this named query in a class mapping:</para> <programlisting><![CDATA[<class name="Person"> <id name="id"> @@ -752,7 +755,7 @@ <para>This even works with stored procedures.</para> - <para>You may even define a query for collection loading:</para> + <para>You can even define a query for collection loading:</para> <programlisting><![CDATA[<set name="employments" inverse="true"> <key/> @@ -768,7 +771,7 @@ ORDER BY STARTDATE ASC, EMPLOYEE ASC </sql-query>]]></programlisting> - <para>You could even define an entity loader that loads a collection by + <para>You can also define an entity loader that loads a collection by join fetching:</para> <programlisting><![CDATA[<sql-query name="person"> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/session_api.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/session_api.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/session_api.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -33,7 +33,7 @@ the developer from the details of the underlying database management system, but also offers <emphasis>state management</emphasis> of objects. This is, contrary to the management of SQL <literal>statements</literal> in common JDBC/SQL - persistence layers, a very natural object-oriented view of persistence in Java + persistence layers, a natural object-oriented view of persistence in Java applications. </para> @@ -59,7 +59,7 @@ is not associated with a Hibernate <literal>Session</literal>. It has no persistent representation in the database and no identifier value has been assigned. Transient instances will be destroyed by the garbage collector if - the application doesn't hold a reference anymore. Use the Hibernate + the application does not hold a reference anymore. Use the Hibernate <literal>Session</literal> to make an object persistent (and let Hibernate take care of the SQL statements that need to be executed for this transition). </para> @@ -71,7 +71,7 @@ however, it is by definition in the scope of a <literal>Session</literal>. Hibernate will detect any changes made to an object in persistent state and synchronize the state with the database when the unit of work completes. - Developers don't execute manual <literal>UPDATE</literal> statements, or + Developers do not execute manual <literal>UPDATE</literal> statements, or <literal>DELETE</literal> statements when an object should be made transient. </para> </listitem> @@ -84,14 +84,14 @@ <literal>Session</literal> at a later point in time, making it (and all the modifications) persistent again. This feature enables a programming model for long running units of work that require user think-time. We call them - <emphasis>application transactions</emphasis>, i.e. a unit of work from the + <emphasis>application transactions</emphasis>, i.e., a unit of work from the point of view of the user. </para> </listitem> </itemizedlist> <para> - We'll now discuss the states and state transitions (and the Hibernate methods that + We will now discuss the states and state transitions (and the Hibernate methods that trigger a transition) in more detail. </para> @@ -119,7 +119,7 @@ is called. If <literal>Cat</literal> has an <literal>assigned</literal> identifier, or a composite key, the identifier should be assigned to the <literal>cat</literal> instance before calling <literal>save()</literal>. - You may also use <literal>persist()</literal> instead of <literal>save()</literal>, + You can also use <literal>persist()</literal> instead of <literal>save()</literal>, with the semantics defined in the EJB3 early draft. </para> @@ -127,7 +127,7 @@ <listitem> <para> <literal>persist()</literal> makes a transient instance persistent. - However, it doesn't guarantee that the identifier value will be assigned to + However, it does not guarantee that the identifier value will be assigned to the persistent instance immediately, the assignment might happen at flush time. <literal>persist()</literal> also guarantees that it will not execute an <literal>INSERT</literal> statement if it is called outside of transaction @@ -147,7 +147,7 @@ </itemizedlist> <para> - Alternatively, you may assign the identifier using an overloaded version + Alternatively, you can assign the identifier using an overloaded version of <literal>save()</literal>. </para> @@ -162,7 +162,7 @@ <para> If the object you make persistent has associated objects (e.g. the <literal>kittens</literal> collection in the previous example), - these objects may be made persistent in any order you like unless you + these objects can be made persistent in any order you like unless you have a <literal>NOT NULL</literal> constraint upon a foreign key column. There is never a risk of violating foreign key constraints. However, you might violate a <literal>NOT NULL</literal> constraint if you @@ -170,10 +170,10 @@ </para> <para> - Usually you don't bother with this detail, as you'll very likely use Hibernate's + Usually you do not bother with this detail, as you will normally use Hibernate's <emphasis>transitive persistence</emphasis> feature to save the associated objects automatically. Then, even <literal>NOT NULL</literal> - constraint violations don't occur - Hibernate will take care of everything. + constraint violations do not occur - Hibernate will take care of everything. Transitive persistence is discussed later in this chapter. </para> @@ -183,10 +183,10 @@ <title>Loading an object</title> <para> - The <literal>load()</literal> methods of <literal>Session</literal> gives you - a way to retrieve a persistent instance if you already know its identifier. - <literal>load()</literal> takes a class object and will load the state into - a newly instantiated instance of that class, in persistent state. + The <literal>load()</literal> methods of <literal>Session</literal> provide + a way of retrieving a persistent instance if you know its identifier. + <literal>load()</literal> takes a class object and loads the state into + a newly instantiated instance of that class in a persistent state. </para> <programlisting><![CDATA[Cat fritz = (Cat) sess.load(Cat.class, generatedId);]]></programlisting> @@ -205,11 +205,11 @@ Set kittens = cat.getKittens();]]></programlisting> <para> - Note that <literal>load()</literal> will throw an unrecoverable exception if + Be aware that <literal>load()</literal> will throw an unrecoverable exception if there is no matching database row. If the class is mapped with a proxy, <literal>load()</literal> just returns an uninitialized proxy and does not actually hit the database until you invoke a method of the proxy. This - behaviour is very useful if you wish to create an association to an object + is useful if you wish to create an association to an object without actually loading it from the database. It also allows multiple instances to be loaded as a batch if <literal>batch-size</literal> is defined for the class mapping. @@ -217,7 +217,7 @@ <para> If you are not certain that a matching row exists, you should use the - <literal>get()</literal> method, which hits the database immediately and + <literal>get()</literal> method which hits the database immediately and returns null if there is no matching row. </para> @@ -229,15 +229,15 @@ return cat;]]></programlisting> <para> - You may even load an object using an SQL <literal>SELECT ... FOR UPDATE</literal>, + You can even load an object using an SQL <literal>SELECT ... FOR UPDATE</literal>, using a <literal>LockMode</literal>. See the API documentation for more information. </para> <programlisting><![CDATA[Cat cat = (Cat) sess.get(Cat.class, id, LockMode.UPGRADE);]]></programlisting> <para> - Note that any associated instances or contained collections are - <emphasis>not</emphasis> selected <literal>FOR UPDATE</literal>, unless you decide + Any associated instances or contained collections will + <emphasis>not</emphasis> be selected <literal>FOR UPDATE</literal>, unless you decide to specify <literal>lock</literal> or <literal>all</literal> as a cascade style for the association. </para> @@ -253,9 +253,9 @@ sess.refresh(cat); //re-read the state (after the trigger executes)]]></programlisting> <para> - An important question usually appears at this point: How much does Hibernate load + How much does Hibernate load from the database and how many SQL <literal>SELECT</literal>s will it use? This - depends on the <emphasis>fetching strategy</emphasis> and is explained in + depends on the <emphasis>fetching strategy</emphasis>. This is explained in <xref linkend="performance-fetching"/>. </para> @@ -265,11 +265,11 @@ <title>Querying</title> <para> - If you don't know the identifiers of the objects you are looking for, + If you do not know the identifiers of the objects you are looking for, you need a query. Hibernate supports an easy-to-use but powerful object oriented query language (HQL). For programmatic query creation, Hibernate supports a sophisticated Criteria and Example query feature (QBC and QBE). - You may also express your query in the native SQL of your database, with + You can also express your query in the native SQL of your database, with optional support from Hibernate for result set conversion into objects. </para> @@ -308,14 +308,14 @@ Set uniqueMothers = new HashSet(mothersWithKittens.list());]]></programlisting> <para> - A query is usually executed by invoking <literal>list()</literal>, the + A query is usually executed by invoking <literal>list()</literal>. The result of the query will be loaded completely into a collection in memory. - Entity instances retrieved by a query are in persistent state. The + Entity instances retrieved by a query are in a persistent state. The <literal>uniqueResult()</literal> method offers a shortcut if you - know your query will only return a single object. Note that queries that + know your query will only return a single object. Queries that make use of eager fetching of collections usually return duplicates of - the root objects (but with their collections initialized). You can filter - these duplicates simply through a <literal>Set</literal>. + the root objects, but with their collections initialized. You can filter + these duplicates through a <literal>Set</literal>. </para> <sect3 id="objectstate-querying-executing-iterate"> @@ -324,7 +324,7 @@ <para> Occasionally, you might be able to achieve better performance by executing the query using the <literal>iterate()</literal> method. - This will only usually be the case if you expect that the actual + This will usually be the case if you expect that the actual entity instances returned by the query will already be in the session or second-level cache. If they are not already cached, <literal>iterate()</literal> will be slower than <literal>list()</literal> @@ -351,7 +351,7 @@ <title>Queries that return tuples</title> <para> - Hibernate queries sometimes return tuples of objects, in which case each tuple + Hibernate queries sometimes return tuples of objects. Each tuple is returned as an array: </para> @@ -373,9 +373,9 @@ <title>Scalar results</title> <para> - Queries may specify a property of a class in the <literal>select</literal> clause. - They may even call SQL aggregate functions. Properties or aggregates are considered - "scalar" results (and not entities in persistent state). + Queries can specify a property of a class in the <literal>select</literal> clause. + They can even call SQL aggregate functions. Properties or aggregates are considered + "scalar" results and not entities in persistent state. </para> <programlisting><![CDATA[Iterator results = sess.createQuery( @@ -402,7 +402,7 @@ named parameters or JDBC-style <literal>?</literal> parameters. <emphasis>Contrary to JDBC, Hibernate numbers parameters from zero.</emphasis> Named parameters are identifiers of the form <literal>:name</literal> in - the query string. The advantages of named parameters are: + the query string. The advantages of named parameters are as follows: </para> <itemizedlist spacing="compact"> @@ -414,7 +414,7 @@ </listitem> <listitem> <para> - they may occur multiple times in the same query + they can occur multiple times in the same query </para> </listitem> <listitem> @@ -448,8 +448,8 @@ <title>Pagination</title> <para> - If you need to specify bounds upon your result set (the maximum number of rows - you want to retrieve and / or the first row you want to retrieve) you should + If you need to specify bounds upon your result set, that is, the maximum number of rows + you want to retrieve and/or the first row you want to retrieve, you can use methods of the <literal>Query</literal> interface: </para> @@ -470,8 +470,8 @@ <para> If your JDBC driver supports scrollable <literal>ResultSet</literal>s, the - <literal>Query</literal> interface may be used to obtain a - <literal>ScrollableResults</literal> object, which allows flexible + <literal>Query</literal> interface can be used to obtain a + <literal>ScrollableResults</literal> object that allows flexible navigation of the query results. </para> @@ -498,8 +498,8 @@ cats.close()]]></programlisting> <para> - Note that an open database connection (and cursor) is required for this - functionality, use <literal>setMaxResult()</literal>/<literal>setFirstResult()</literal> + Note that an open database connection and cursor is required for this + functionality. Use <literal>setMaxResult()</literal>/<literal>setFirstResult()</literal> if you need offline pagination functionality. </para> @@ -509,9 +509,9 @@ <title>Externalizing named queries</title> <para> - You may also define named queries in the mapping document. (Remember to use a + You can also define named queries in the mapping document. Remember to use a <literal>CDATA</literal> section if your query contains characters that could - be interpreted as markup.) + be interpreted as markup. </para> <programlisting><![CDATA[<query name="ByNameAndMaximumWeight"><![CDATA[ @@ -530,8 +530,8 @@ List cats = q.list();]]></programlisting> <para> - Note that the actual program code is independent of the query language that - is used, you may also define native SQL queries in metadata, or migrate + The actual program code is independent of the query language that + is used. You can also define native SQL queries in metadata, or migrate existing queries to Hibernate by placing them in mapping files. </para> @@ -539,7 +539,7 @@ Also note that a query declaration inside a <literal>&lt;hibernate-mapping&gt;</literal> element requires a global unique name for the query, while a query declaration inside a <literal>&lt;class&gt;</literal> element is made unique automatically by prepending the - fully qualified name of the class, for example + fully qualified name of the class. For example <literal>eg.Cat.ByNameAndMaximumWeight</literal>. </para> @@ -550,8 +550,8 @@ <sect2 id="objectstate-filtering" revision="1"> <title>Filtering collections</title> <para> - A collection <emphasis>filter</emphasis> is a special type of query that may be applied to - a persistent collection or array. The query string may refer to <literal>this</literal>, + A collection <emphasis>filter</emphasis> is a special type of query that can be applied to + a persistent collection or array. The query string can refer to <literal>this</literal>, meaning the current collection element. </para> @@ -563,14 +563,14 @@ );]]></programlisting> <para> - The returned collection is considered a bag, and it's a copy of the given - collection. The original collection is not modified (this is contrary to - the implication of the name "filter", but consistent with expected behavior). + The returned collection is considered a bag that is a copy of the given + collection. The original collection is not modified. This is contrary to + the implication of the name "filter", but consistent with expected behavior. </para> <para> - Observe that filters do not require a <literal>from</literal> clause (though they may have - one if required). Filters are not limited to returning the collection elements themselves. + Observe that filters do not require a <literal>from</literal> clause, although they can have + one if required. Filters are not limited to returning the collection elements themselves. </para> <programlisting><![CDATA[Collection blackKittenMates = session.createFilter( @@ -580,7 +580,7 @@ <para> Even an empty filter query is useful, e.g. to load a subset of elements in a - huge collection: + large collection: </para> <programlisting><![CDATA[Collection tenKittens = session.createFilter( @@ -594,7 +594,7 @@ <title>Criteria queries</title> <para> - HQL is extremely powerful but some developers prefer to build queries dynamically, + HQL is extremely powerful, but some developers prefer to build queries dynamically using an object-oriented API, rather than building query strings. Hibernate provides an intuitive <literal>Criteria</literal> query API for these cases: </para> @@ -615,10 +615,10 @@ <title>Queries in native SQL</title> <para> - You may express a query in SQL, using <literal>createSQLQuery()</literal> and - let Hibernate take care of the mapping from result sets to objects. Note - that you may at any time call <literal>session.connection()</literal> and - use the JDBC <literal>Connection</literal> directly. If you chose to use the + You can express a query in SQL, using <literal>createSQLQuery()</literal> and + let Hibernate manage the mapping from result sets to objects. + You can at any time call <literal>session.connection()</literal> and + use the JDBC <literal>Connection</literal> directly. If you choose to use the Hibernate API, you must enclose SQL aliases in braces: </para> @@ -634,7 +634,7 @@ .list()]]></programlisting> <para> - SQL queries may contain named and positional parameters, just like Hibernate queries. + SQL queries can contain named and positional parameters, just like Hibernate queries. More information about native SQL queries in Hibernate can be found in <xref linkend="querysql"/>. </para> @@ -647,14 +647,14 @@ <title>Modifying persistent objects</title> <para> - <emphasis>Transactional persistent instances</emphasis> (ie. objects loaded, saved, created or - queried by the <literal>Session</literal>) may be manipulated by the application + <emphasis>Transactional persistent instances</emphasis> (i.e. objects loaded, saved, created or + queried by the <literal>Session</literal>) can be manipulated by the application, and any changes to persistent state will be persisted when the <literal>Session</literal> - is <emphasis>flushed</emphasis> (discussed later in this chapter). There is no need + is <emphasis>flushed</emphasis>. This is discussed later in this chapter. There is no need to call a particular method (like <literal>update()</literal>, which has a different - purpose) to make your modifications persistent. So the most straightforward way to update - the state of an object is to <literal>load()</literal> it, - and then manipulate it directly, while the <literal>Session</literal> is open: + purpose) to make your modifications persistent. The most straightforward way to update + the state of an object is to <literal>load()</literal> it + and then manipulate it directly while the <literal>Session</literal> is open: </para> <programlisting><![CDATA[DomesticCat cat = (DomesticCat) sess.load( Cat.class, new Long(69) ); @@ -662,24 +662,25 @@ sess.flush(); // changes to cat are automatically detected and persisted]]></programlisting> <para> - Sometimes this programming model is inefficient since it would require both an SQL - <literal>SELECT</literal> (to load an object) and an SQL <literal>UPDATE</literal> - (to persist its updated state) in the same session. Therefore Hibernate offers an - alternate approach, using detached instances. + Sometimes this programming model is inefficient, as it requires in the same session both an SQL + <literal>SELECT</literal> to load an object and an SQL <literal>UPDATE</literal> + to persist its updated state. Hibernate offers an + alternate approach by using detached instances. </para> - <para> - <emphasis>Note that Hibernate does not offer its own API for direct execution of + <important><para> + Hibernate does not offer its own API for direct execution of <literal>UPDATE</literal> or <literal>DELETE</literal> statements. Hibernate is a - <emphasis>state management</emphasis> service, you don't have to think in + <emphasis>state management</emphasis> service, you do not have to think in <emphasis>statements</emphasis> to use it. JDBC is a perfect API for executing SQL statements, you can get a JDBC <literal>Connection</literal> at any time by calling <literal>session.connection()</literal>. Furthermore, the notion of mass operations conflicts with object/relational mapping for online transaction processing-oriented applications. Future versions of Hibernate - may however provide special mass operation functions. See <xref linkend="batch"/> - for some possible batch operation tricks.</emphasis> + can, however, provide special mass operation functions. See <xref linkend="batch"/> + for some possible batch operation tricks. </para> +</important> </sect1> @@ -690,7 +691,7 @@ Many applications need to retrieve an object in one transaction, send it to the UI layer for manipulation, then save the changes in a new transaction. Applications that use this kind of approach in a high-concurrency environment - usually use versioned data to ensure isolation for the "long" unit of work. + usually use versioned data to ensure isolation for the "long" unit of work. </para> <para> @@ -713,29 +714,29 @@ <para> If the <literal>Cat</literal> with identifier <literal>catId</literal> had already - been loaded by <literal>secondSession</literal> when the application tried to + been loaded by <literal>secondSession</literal> when the application tried to reattach it, an exception would have been thrown. </para> <para> - Use <literal>update()</literal> if you are sure that the session does - not contain an already persistent instance with the same identifier, and + Use <literal>update()</literal> if you are certain that the session does + not contain an already persistent instance with the same identifier. Use <literal>merge()</literal> if you want to merge your modifications at any time without consideration of the state of the session. In other words, <literal>update()</literal> is usually the first method you would call in a fresh session, ensuring that - reattachment of your detached instances is the first operation that is executed. + the reattachment of your detached instances is the first operation that is executed. </para> <para> The application should individually <literal>update()</literal> detached instances - reachable from the given detached instance if and <emphasis>only</emphasis> if it wants - their state also updated. This can be automated of course, using <emphasis>transitive - persistence</emphasis>, see <xref linkend="objectstate-transitive"/>. + that are reachable from the given detached instance <emphasis>only</emphasis> if it wants + their state to be updated. This can be automated using <emphasis>transitive + persistence</emphasis>. See <xref linkend="objectstate-transitive"/> for more information. </para> <para> The <literal>lock()</literal> method also allows an application to reassociate - an object with a new session. However, the detached instance has to be unmodified! + an object with a new session. However, the detached instance has to be unmodified. </para> <programlisting><![CDATA[//just reassociate: @@ -747,7 +748,7 @@ <para> Note that <literal>lock()</literal> can be used with various - <literal>LockMode</literal>s, see the API documentation and the + <literal>LockMode</literal>s. See the API documentation and the chapter on transaction handling for more information. Reattachment is not the only usecase for <literal>lock()</literal>. </para> @@ -850,8 +851,8 @@ </listitem> <listitem> <para> - if the object is versioned (by a <literal>&lt;version&gt;</literal> or - <literal>&lt;timestamp&gt;</literal>), and the version property value + if the object is versioned by a <literal>&lt;version&gt;</literal> or + <literal>&lt;timestamp&gt;</literal>, and the version property value is the same value assigned to a newly instantiated object, <literal>save()</literal> it </para> @@ -901,15 +902,15 @@ <para> <literal>Session.delete()</literal> will remove an object's state from the database. - Of course, your application might still hold a reference to a deleted object. - It's best to think of <literal>delete()</literal> as making a persistent instance + Your application, however, can still hold a reference to a deleted object. + It is best to think of <literal>delete()</literal> as making a persistent instance, transient. </para> <programlisting><![CDATA[sess.delete(cat);]]></programlisting> <para> - You may delete objects in any order you like, without risk of foreign key + You can delete objects in any order, without risk of foreign key constraint violations. It is still possible to violate a <literal>NOT NULL</literal> constraint on a foreign key column by deleting objects in the wrong order, e.g. if you delete the parent, but forget to delete the @@ -922,7 +923,7 @@ <title>Replicating object between two different datastores</title> <para> - It is occasionally useful to be able to take a graph of persistent instances + It is sometimes useful to be able to take a graph of persistent instances and make them persistent in a different datastore, without regenerating identifier values. </para> @@ -943,31 +944,31 @@ <para> The <literal>ReplicationMode</literal> determines how <literal>replicate()</literal> - will deal with conflicts with existing rows in the database. + will deal with conflicts with existing rows in the database: </para> <itemizedlist spacing="compact"> <listitem> <para> - <literal>ReplicationMode.IGNORE</literal> - ignore the object when there is + <literal>ReplicationMode.IGNORE</literal>: ignores the object when there is an existing database row with the same identifier </para> </listitem> <listitem> <para> - <literal>ReplicationMode.OVERWRITE</literal> - overwrite any existing database + <literal>ReplicationMode.OVERWRITE</literal>: overwrites any existing database row with the same identifier </para> </listitem> <listitem> <para> - <literal>ReplicationMode.EXCEPTION</literal> - throw an exception if there is + <literal>ReplicationMode.EXCEPTION</literal>: throws an exception if there is an existing database row with the same identifier </para> </listitem> <listitem> <para> - <literal>ReplicationMode.LATEST_VERSION</literal> - overwrite the row if its + <literal>ReplicationMode.LATEST_VERSION</literal>: overwrites the row if its version number is earlier than the version number of the object, or ignore the object otherwise </para> @@ -986,10 +987,10 @@ <title>Flushing the Session</title> <para> - From time to time the <literal>Session</literal> will execute the SQL statements + Sometimes the <literal>Session</literal> will execute the SQL statements needed to synchronize the JDBC connection's state with the state of objects held in - memory. This process, <emphasis>flush</emphasis>, occurs by default at the following - points + memory. This process, called <emphasis>flush</emphasis>, occurs by default at the following + points: </para> <itemizedlist spacing="compact"> @@ -1011,13 +1012,13 @@ </itemizedlist> <para> - The SQL statements are issued in the following order + The SQL statements are issued in the following order: </para> <orderedlist spacing="compact"> <listitem> <para> - all entity insertions, in the same order the corresponding objects + all entity insertions in the same order the corresponding objects were saved using <literal>Session.save()</literal> </para> </listitem> @@ -1043,30 +1044,30 @@ </listitem> <listitem> <para> - all entity deletions, in the same order the corresponding objects + all entity deletions in the same order the corresponding objects were deleted using <literal>Session.delete()</literal> </para> </listitem> </orderedlist> <para> - (An exception is that objects using <literal>native</literal> ID generation are - inserted when they are saved.) + An exception is that objects using <literal>native</literal> ID generation are + inserted when they are saved. </para> <para> - Except when you explicity <literal>flush()</literal>, there are absolutely no + Except when you explicitly <literal>flush()</literal>, there are absolutely no guarantees about <emphasis>when</emphasis> the <literal>Session</literal> executes the JDBC calls, only the <emphasis>order</emphasis> in which they are executed. However, Hibernate does guarantee that the <literal>Query.list(..)</literal> - will never return stale data; nor will they return the wrong data. + will never return stale or incorrect data. </para> <para> It is possible to change the default behavior so that flush occurs less frequently. The <literal>FlushMode</literal> class defines three different modes: only flush - at commit time (and only when the Hibernate <literal>Transaction</literal> API - is used), flush automatically using the explained routine, or never flush unless + at commit time when the Hibernate <literal>Transaction</literal> API + is used, flush automatically using the explained routine, or never flush unless <literal>flush()</literal> is called explicitly. The last mode is useful for long running units of work, where a <literal>Session</literal> is kept open and disconnected for a long time (see <xref linkend="transactions-optimistic-longsession"/>). @@ -1108,17 +1109,17 @@ If the children in a parent/child relationship would be value typed (e.g. a collection of addresses or strings), their life cycle would depend on the parent and no further action would be required for convenient "cascading" of state changes. - When the parent is saved, the value-typed child objects are saved as - well, when the parent is deleted, the children will be deleted, etc. This - even works for operations such as the removal of a child from the collection; - Hibernate will detect this and, since value-typed objects can't have shared - references, delete the child from the database. + When the parent is saved, the value-typed child objects are saved and + when the parent is deleted, the children will be deleted, etc. This + works for operations such as the removal of a child from the collection. + Since value-typed objects cannot have shared + references, Hibernate will detect this and delete the child from the database. </para> <para> Now consider the same scenario with parent and child objects being entities, not value-types (e.g. categories and items, or parent and child cats). Entities - have their own life cycle, support shared references (so removing an entity from + have their own life cycle and support shared references. Removing an entity from the collection does not mean it can be deleted), and there is by default no cascading of state from one entity to any other associated entities. Hibernate does not implement <emphasis>persistence by reachability</emphasis> by default. @@ -1142,7 +1143,7 @@ <programlisting><![CDATA[<one-to-one name="person" cascade="persist,delete,lock"/>]]></programlisting> <para> - You may even use <literal>cascade="all"</literal> to specify that <emphasis>all</emphasis> + You can even use <literal>cascade="all"</literal> to specify that <emphasis>all</emphasis> operations should be cascaded along the association. The default <literal>cascade="none"</literal> specifies that no operations are to be cascaded. </para> @@ -1161,7 +1162,7 @@ <itemizedlist spacing="compact"> <listitem> <para> - It doesn't usually make sense to enable cascade on a <literal>&lt;many-to-one&gt;</literal> + It does not usually make sense to enable cascade on a <literal>&lt;many-to-one&gt;</literal> or <literal>&lt;many-to-many&gt;</literal> association. Cascade is often useful for <literal>&lt;one-to-one&gt;</literal> and <literal>&lt;one-to-many&gt;</literal> associations. @@ -1190,7 +1191,7 @@ parent results in save/update/delete of the child or children. </para> <para> - Futhermore, a mere reference to a child from a persistent parent will result in + Furthermore, a mere reference to a child from a persistent parent will result in save/update of the child. This metaphor is incomplete, however. A child which becomes unreferenced by its parent is <emphasis>not</emphasis> automatically deleted, except in the case of a <literal>&lt;one-to-many&gt;</literal> association mapped with @@ -1242,7 +1243,7 @@ Finally, note that cascading of operations can be applied to an object graph at <emphasis>call time</emphasis> or at <emphasis>flush time</emphasis>. All operations, if enabled, are cascaded to associated entities reachable when the operation is - executed. However, <literal>save-upate</literal> and <literal>delete-orphan</literal> + executed. However, <literal>save-update</literal> and <literal>delete-orphan</literal> are transitive for all associated entities reachable during flush of the <literal>Session</literal>. </para> @@ -1253,16 +1254,16 @@ <title>Using metadata</title> <para> - Hibernate requires a very rich meta-level model of all entity and value types. From time - to time, this model is very useful to the application itself. For example, the application + Hibernate requires a rich meta-level model of all entity and value types. + This model can be useful to the application itself. For example, the application might use Hibernate's metadata to implement a "smart" deep-copy algorithm that understands - which objects should be copied (eg. mutable value types) and which should not (eg. + which objects should be copied (eg. mutable value types) and which objects that should not (e.g. immutable value types and, possibly, associated entities). </para> <para> Hibernate exposes metadata via the <literal>ClassMetadata</literal> and <literal>CollectionMetadata</literal> interfaces and the <literal>Type</literal> - hierarchy. Instances of the metadata interfaces may be obtained from the + hierarchy. Instances of the metadata interfaces can be obtained from the <literal>SessionFactory</literal>. </para> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/toolset_guide.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/toolset_guide.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/toolset_guide.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -30,57 +30,57 @@ <para> Roundtrip engineering with Hibernate is possible using a set of Eclipse plugins, - commandline tools, as well as Ant tasks. + commandline tools, and Ant tasks. </para> <para> - The <emphasis>Hibernate Tools</emphasis> currently include plugins for the Eclipse + <emphasis>Hibernate Tools</emphasis> currently include plugins for the Eclipse IDE as well as Ant tasks for reverse engineering of existing databases: </para> <itemizedlist> <listitem><para> - <emphasis>Mapping Editor:</emphasis> An editor for Hibernate XML mapping files, - supporting auto-completion and syntax highlighting. It also supports semantic - auto-completion for class names and property/field names, making it much more versatile than a normal XML editor. + <emphasis>Mapping Editor:</emphasis> an editor for Hibernate XML mapping files that + supports auto-completion and syntax highlighting. It also supports semantic + auto-completion for class names and property/field names, making it more versatile than a normal XML editor. </para></listitem> <listitem><para> - <emphasis>Console:</emphasis> The console is a new view in Eclipse. In addition to - a tree overview of your console configurations, you also get an interactive view + <emphasis>Console:</emphasis> the console is a new view in Eclipse. In addition to + a tree overview of your console configurations, you are also provided with an interactive view of your persistent classes and their relationships. The console allows you to execute HQL queries against your database and browse the result directly in Eclipse. </para></listitem> <listitem><para> - <emphasis>Development Wizards:</emphasis> Several wizards are provided with the - Hibernate Eclipse tools; you can use a wizard to quickly generate Hibernate configuration - (cfg.xml) files, or you may even completely reverse engineer an existing database schema + <emphasis>Development Wizards:</emphasis> several wizards are provided with the + Hibernate Eclipse tools. You can use a wizard to quickly generate Hibernate configuration + (cfg.xml) files, or to reverse engineer an existing database schema into POJO source files and Hibernate mapping files. The reverse engineering wizard supports customizable templates. </para></listitem> <listitem><para> - <emphasis>Ant Tasks:</emphasis> +<!-- <emphasis>Ant Tasks:</emphasis> --> </para></listitem> </itemizedlist> <para> - Please refer to the <emphasis>Hibernate Tools</emphasis> package and it's documentation + Please refer to the <emphasis>Hibernate Tools</emphasis> package documentation for more information. </para> <para> - However, the Hibernate main package comes bundled with an integrated tool (it can even - be used from "inside" Hibernate on-the-fly): <emphasis>SchemaExport</emphasis> aka - <literal>hbm2ddl</literal>. + However, the Hibernate main package comes bundled with an integrated tool : <emphasis>SchemaExport</emphasis> aka + <literal>hbm2ddl</literal>.It can even + be used from "inside" Hibernate. </para> <sect1 id="toolsetguide-s1" revision="2"> <title>Automatic schema generation</title> <para> - DDL may be generated from your mapping files by a Hibernate utility. The generated - schema includes referential integrity constraints (primary and foreign keys) for + DDL can be generated from your mapping files by a Hibernate utility. The generated + schema includes referential integrity constraints, primary and foreign keys, for entity and collection tables. Tables and sequences are also created for mapped identifier generators. </para> @@ -88,11 +88,11 @@ <para> You <emphasis>must</emphasis> specify a SQL <literal>Dialect</literal> via the <literal>hibernate.dialect</literal> property when using this tool, as DDL - is highly vendor specific. + is highly vendor-specific. </para> <para> - First, customize your mapping files to improve the generated schema. + First, you must customize your mapping files to improve the generated schema. The next section covers schema customization. </para> <sect2 id="toolsetguide-s1-2" revision="3"> @@ -100,7 +100,7 @@ <para> Many Hibernate mapping elements define optional attributes named <literal>length</literal>, - <literal>precision</literal> and <literal>scale</literal>. You may set the length, precision + <literal>precision</literal> and <literal>scale</literal>. You can set the length, precision and scale of a column with this attribute. </para> @@ -109,9 +109,9 @@ <programlisting><![CDATA[<property name="balance" precision="12" scale="2"/>]]></programlisting> <para> - Some tags also accept a <literal>not-null</literal> attribute (for generating a - <literal>NOT NULL</literal> constraint on table columns) and a <literal>unique</literal> - attribute (for generating <literal>UNIQUE</literal> constraint on table columns). + Some tags also accept a <literal>not-null</literal> attribute for generating a + <literal>NOT NULL</literal> constraint on table columns, and a <literal>unique</literal> + attribute for generating <literal>UNIQUE</literal> constraint on table columns. </para> <programlisting><![CDATA[<many-to-one name="bar" column="barId" not-null="true"/>]]></programlisting> @@ -119,10 +119,10 @@ <programlisting><![CDATA[<element column="serialNumber" type="long" not-null="true" unique="true"/>]]></programlisting> <para> - A <literal>unique-key</literal> attribute may be used to group columns in - a single unique key constraint. Currently, the specified value of the + A <literal>unique-key</literal> attribute can be used to group columns in + a single, unique key constraint. Currently, the specified value of the <literal>unique-key</literal> attribute is <emphasis>not</emphasis> used - to name the constraint in the generated DDL, only to group the columns in + to name the constraint in the generated DDL. It is only used to group the columns in the mapping file. </para> @@ -131,15 +131,15 @@ <para> An <literal>index</literal> attribute specifies the name of an index that - will be created using the mapped column or columns. Multiple columns may be - grouped into the same index, simply by specifying the same index name. + will be created using the mapped column or columns. Multiple columns can be + grouped into the same index by simply specifying the same index name. </para> <programlisting><![CDATA[<property name="lastName" index="CustName"/> <property name="firstName" index="CustName"/>]]></programlisting> <para> - A <literal>foreign-key</literal> attribute may be used to override the name + A <literal>foreign-key</literal> attribute can be used to override the name of any generated foreign key constraint. </para> @@ -157,9 +157,9 @@ </property>]]></programlisting> <para> - The <literal>default</literal> attribute lets you specify a default value for - a column (you should assign the same value to the mapped property before - saving a new instance of the mapped class). + The <literal>default</literal> attribute allows you to specify a default value for + a column.You should assign the same value to the mapped property before + saving a new instance of the mapped class. </para> <programlisting><![CDATA[<property name="credits" type="integer" insert="false"> @@ -193,6 +193,8 @@ </class>]]></programlisting> + <para>The following table summarizes these optional attributes.</para> + <table frame="topbot" id="schemattributes-summary" revision="2"> <title>Summary</title> <tgroup cols="3"> @@ -225,7 +227,7 @@ <row> <entry><literal>not-null</literal></entry> <entry><literal>true|false</literal></entry> - <entry>specfies that the column should be non-nullable</entry> + <entry>specifies that the column should be non-nullable</entry> </row> <row> <entry><literal>unique</literal></entry> @@ -299,7 +301,7 @@ <para> This results in a <literal>comment on table</literal> or <literal>comment on column</literal> statement in the generated - DDL (where supported). + DDL where supported. </para> </sect2> @@ -311,8 +313,10 @@ The <literal>SchemaExport</literal> tool writes a DDL script to standard out and/or executes the DDL statements. </para> - - <para> + + <para>The following table displays the <literal>SchemaExport</literal> command line options</para> + + <para> <literal>java -cp </literal><emphasis>hibernate_classpaths</emphasis> <literal>org.hibernate.tool.hbm2ddl.SchemaExport</literal> <emphasis>options mapping_files</emphasis> </para> @@ -331,7 +335,7 @@ <tbody> <row> <entry><literal>--quiet</literal></entry> - <entry>don't output the script to stdout</entry> + <entry>do not output the script to stdout</entry> </row> <row> <entry><literal>--drop</literal></entry> @@ -343,7 +347,7 @@ </row> <row> <entry><literal>--text</literal></entry> - <entry>don't export to the database</entry> + <entry>do not export to the database</entry> </row> <row> <entry><literal>--output=my_schema.ddl</literal></entry> @@ -374,7 +378,7 @@ </table> <para> - You may even embed <literal>SchemaExport</literal> in your application: + You can even embed <literal>SchemaExport</literal> in your application: </para> <programlisting><![CDATA[Configuration cfg = ....; @@ -386,7 +390,7 @@ <title>Properties</title> <para> - Database properties may be specified + Database properties can be specified: </para> <itemizedlist spacing="compact"> @@ -475,7 +479,7 @@ <para> The <literal>SchemaUpdate</literal> tool will update an existing schema with "incremental" changes. - Note that <literal>SchemaUpdate</literal> depends heavily upon the JDBC metadata API, so it will + The <literal>SchemaUpdate</literal> depends upon the JDBC metadata API and, as such, will not work with all JDBC drivers. </para> @@ -498,11 +502,11 @@ <tbody> <row> <entry><literal>--quiet</literal></entry> - <entry>don't output the script to stdout</entry> + <entry>do not output the script to stdout</entry> </row> <row> <entry><literal>--text</literal></entry> - <entry>don't export the script to the database</entry> + <entry>do not export the script to the database</entry> </row> <row> <entry><literal>--naming=eg.MyNamingStrategy</literal></entry> @@ -521,7 +525,7 @@ </table> <para> - You may embed <literal>SchemaUpdate</literal> in your application: + You can embed <literal>SchemaUpdate</literal> in your application: </para> <programlisting><![CDATA[Configuration cfg = ....; @@ -557,15 +561,15 @@ <para> The <literal>SchemaValidator</literal> tool will validate that the existing database schema "matches" - your mapping documents. Note that <literal>SchemaValidator</literal> depends heavily upon the JDBC - metadata API, so it will not work with all JDBC drivers. This tool is extremely useful for testing. + your mapping documents. The <literal>SchemaValidator</literal> depends heavily upon the JDBC + metadata API and, as such, will not work with all JDBC drivers. This tool is extremely useful for testing. </para> <para> <literal>java -cp </literal><emphasis>hibernate_classpaths</emphasis> <literal>org.hibernate.tool.hbm2ddl.SchemaValidator</literal> <emphasis>options mapping_files</emphasis> </para> - +<para>The following table displays the <literal>SchemaValidator</literal> command line options: <table frame="topbot"> <title><literal>SchemaValidator</literal> Command Line Options</title> <tgroup cols="2"> @@ -595,7 +599,7 @@ </table> <para> - You may embed <literal>SchemaValidator</literal> in your application: + You can embed <literal>SchemaValidator</literal> in your application: </para> <programlisting><![CDATA[Configuration cfg = ....; Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/transactions.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/transactions.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/transactions.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -26,32 +26,32 @@ <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"> <chapter id="transactions" revision="2"> - <title>Transactions And Concurrency</title> + <title>Transactions and Concurrency</title> <para> - The most important point about Hibernate and concurrency control is that it is very + The most important point about Hibernate and concurrency control is that it is easy to understand. Hibernate directly uses JDBC connections and JTA resources without - adding any additional locking behavior. We highly recommend you spend some time with the + adding any additional locking behavior. It is recommended that you spend some time with the JDBC, ANSI, and transaction isolation specification of your database management system. </para> <para> Hibernate does not lock objects in memory. Your application can expect the behavior as - defined by the isolation level of your database transactions. Note that thanks to the + defined by the isolation level of your database transactions. Through <literal>Session</literal>, which is also a transaction-scoped cache, Hibernate - provides repeatable reads for lookup by identifier and entity queries (not - reporting queries that return scalar values). + provides repeatable reads for lookup by identifier and entity queries and not + reporting queries that return scalar values. </para> <para> In addition to versioning for automatic optimistic concurrency control, Hibernate also - offers a (minor) API for pessimistic locking of rows, using the - <literal>SELECT FOR UPDATE</literal> syntax. Optimistic concurrency control and + offers, using the + <literal>SELECT FOR UPDATE</literal> syntax, a (minor) API for pessimistic locking of rows. Optimistic concurrency control and this API are discussed later in this chapter. </para> <para> - We start the discussion of concurrency control in Hibernate with the granularity of + The discussion of concurrency control in Hibernate begins with the granularity of <literal>Configuration</literal>, <literal>SessionFactory</literal>, and <literal>Session</literal>, as well as database transactions and long conversations. </para> @@ -60,61 +60,59 @@ <title>Session and transaction scopes</title> <para> - A <literal>SessionFactory</literal> is an expensive-to-create, threadsafe object + A <literal>SessionFactory</literal> is an expensive-to-create, threadsafe object, intended to be shared by all application threads. It is created once, usually on application startup, from a <literal>Configuration</literal> instance. </para> <para> A <literal>Session</literal> is an inexpensive, non-threadsafe object that should be - used once, for a single request, a conversation, single unit of work, and then discarded. - A <literal>Session</literal> will not obtain a JDBC <literal>Connection</literal> - (or a <literal>Datasource</literal>) unless it is needed, hence consume no + used once and then discarded for: a single request, a conversation or a single unit of work. + A <literal>Session</literal> will not obtain a JDBC <literal>Connection</literal>, + or a <literal>Datasource</literal>, unless it is needed. It will not consume any resources until used. </para> <para> - To complete this picture you also have to think about database transactions. A - database transaction has to be as short as possible, to reduce lock contention in - the database. Long database transactions will prevent your application from scaling - to highly concurrent load. Hence, it is almost never good design to hold a - database transaction open during user think time, until the unit of work is + In order to reduce lock contention in the database, a database transaction has to be as short as possible. + Long database transactions will prevent your application from scaling + to a highly concurrent load. It is not recommended that you hold a + database transaction open during user think time until the unit of work is complete. </para> <para> What is the scope of a unit of work? Can a single Hibernate <literal>Session</literal> - span several database transactions or is this a one-to-one relationship of scopes? When + span several database transactions, or is this a one-to-one relationship of scopes? When should you open and close a <literal>Session</literal> and how do you demarcate the - database transaction boundaries? + database transaction boundaries? These questions are addressed in the following sections. </para> <sect2 id="transactions-basics-uow" revision="1"> <title>Unit of work</title> <para> - First, don't use the <emphasis>session-per-operation</emphasis> antipattern, that is, - don't open and close a <literal>Session</literal> for every simple database call in - a single thread! Of course, the same is true for database transactions. Database calls - in an application are made using a planned sequence, they are grouped into atomic - units of work. (Note that this also means that auto-commit after every single - SQL statement is useless in an application, this mode is intended for ad-hoc SQL - console work. Hibernate disables, or expects the application server to do so, - auto-commit mode immediately.) Database transactions are never optional, all - communication with a database has to occur inside a transaction, no matter if - you read or write data. As explained, auto-commit behavior for reading data + Do not use the <emphasis>session-per-operation</emphasis> antipattern: + do not open and close a <literal>Session</literal> for every simple database call in + a single thread. The same is true for database transactions. Database calls + in an application are made using a planned sequence; they are grouped into atomic + units of work. This also means that auto-commit after every single + SQL statement is useless in an application as this mode is intended for ad-hoc SQL + console work. Hibernate disables, or expects the application server to disable, + auto-commit mode immediately. Database transactions are never optional. All + communication with a database has to occur inside a transaction. Auto-commit behavior for reading data should be avoided, as many small transactions are unlikely to perform better than - one clearly defined unit of work. The latter is also much more maintainable + one clearly defined unit of work. The latter is also more maintainable and extensible. </para> <para> The most common pattern in a multi-user client/server application is <emphasis>session-per-request</emphasis>. In this model, a request from the client - is sent to the server (where the Hibernate persistence layer runs), a new Hibernate + is sent to the server, where the Hibernate persistence layer runs. A new Hibernate <literal>Session</literal> is opened, and all database operations are executed in this unit - of work. Once the work has been completed (and the response for the client has been prepared), - the session is flushed and closed. You would also use a single database transaction to + of work. On completion of the work, and once the response for the client has been prepared, + the session is flushed and closed. Use a single database transaction to serve the clients request, starting and committing it when you open and close the <literal>Session</literal>. The relationship between the two is one-to-one and this model is a perfect fit for many applications. @@ -122,34 +120,33 @@ <para> The challenge lies in the implementation. Hibernate provides built-in management of - the "current session" to simplify this pattern. All you have to do is start a + the "current session" to simplify this pattern. Start a transaction when a server request has to be processed, and end the transaction - before the response is sent to the client. You can do this in any way you - like, common solutions are <literal>ServletFilter</literal>, AOP interceptor with a + before the response is sent to the client. Common solutions are <literal>ServletFilter</literal>, AOP interceptor with a pointcut on the service methods, or a proxy/interception container. An EJB container is a standardized way to implement cross-cutting aspects such as transaction - demarcation on EJB session beans, declaratively with CMT. If you decide to - use programmatic transaction demarcation, prefer the Hibernate <literal>Transaction</literal> - API shown later in this chapter, for ease of use and code portability. + demarcation on EJB session beans, declaratively with CMT. If you + use programmatic transaction demarcation, for ease of use and code portability use the Hibernate <literal>Transaction</literal> + API shown later in this chapter. </para> <para> Your application code can access a "current session" to process the request - by simply calling <literal>sessionFactory.getCurrentSession()</literal> anywhere - and as often as needed. You will always get a <literal>Session</literal> scoped + by calling <literal>sessionFactory.getCurrentSession()</literal>. + You will always get a <literal>Session</literal> scoped to the current database transaction. This has to be configured for either resource-local or JTA environments, see <xref linkend="architecture-current-session"/>. </para> <para> - Sometimes it is convenient to extend the scope of a <literal>Session</literal> and + You can extend the scope of a <literal>Session</literal> and database transaction until the "view has been rendered". This is especially useful in servlet applications that utilize a separate rendering phase after the request - has been processed. Extending the database transaction until view rendering is - complete is easy to do if you implement your own interceptor. However, it is not - easily doable if you rely on EJBs with container-managed transactions, as a + has been processed. Extending the database transaction until view rendering, is achieved by implementing + your own interceptor. However, this will be difficult + if you rely on EJBs with container-managed transactions. A transaction will be completed when an EJB method returns, before rendering of any - view can start. See the Hibernate website and forum for tips and examples around + view can start. See the Hibernate website and forum for tips and examples relating to this <emphasis>Open Session in View</emphasis> pattern. </para> @@ -159,9 +156,9 @@ <title>Long conversations</title> <para> - The session-per-request pattern is not the only useful concept you can use to design - units of work. Many business processes require a whole series of interactions with the user - interleaved with database accesses. In web and enterprise applications it is + The session-per-request pattern is not the only way of designing + units of work. Many business processes require a whole series of interactions with the user that are + interleaved with database accesses. In web and enterprise applications, it is not acceptable for a database transaction to span a user interaction. Consider the following example: </para> @@ -169,82 +166,82 @@ <itemizedlist> <listitem> <para> - The first screen of a dialog opens, the data seen by the user has been loaded in + The first screen of a dialog opens. The data seen by the user has been loaded in a particular <literal>Session</literal> and database transaction. The user is free to modify the objects. </para> </listitem> <listitem> <para> - The user clicks "Save" after 5 minutes and expects his modifications to be made - persistent; he also expects that he was the only person editing this information and - that no conflicting modification can occur. + The user clicks "Save" after 5 minutes and expects their modifications to be made + persistent. The user also expects that they were the only person editing this information and + that no conflicting modification has occurred. </para> </listitem> </itemizedlist> <para> - We call this unit of work, from the point of view of the user, a long running - <emphasis>conversation</emphasis> (or <emphasis>application transaction</emphasis>). - There are many ways how you can implement this in your application. + From the point of view of the user, we call this unit of work a long-running + <emphasis>conversation</emphasis> or <emphasis>application transaction</emphasis>. + There are many ways to implement this in your application. </para> <para> A first naive implementation might keep the <literal>Session</literal> and database transaction open during user think time, with locks held in the database to prevent - concurrent modification, and to guarantee isolation and atomicity. This is of course + concurrent modification and to guarantee isolation and atomicity. This is an anti-pattern, since lock contention would not allow the application to scale with the number of concurrent users. </para> <para> - Clearly, we have to use several database transactions to implement the conversation. + You have to use several database transactions to implement the conversation. In this case, maintaining isolation of business processes becomes the partial responsibility of the application tier. A single conversation usually spans several database transactions. It will be atomic if only one of - these database transactions (the last one) stores the updated data, all others - simply read data (e.g. in a wizard-style dialog spanning several request/response + these database transactions (the last one) stores the updated data. All others + simply read data (for example, in a wizard-style dialog spanning several request/response cycles). This is easier to implement than it might sound, especially if - you use Hibernate's features: + you utilize some of Hibernate's features: </para> <itemizedlist> <listitem> <para> - <emphasis>Automatic Versioning</emphasis> - Hibernate can do automatic - optimistic concurrency control for you, it can automatically detect - if a concurrent modification occurred during user think time. Usually - we only check at the end of the conversation. + <emphasis>Automatic Versioning</emphasis>: Hibernate can perform automatic + optimistic concurrency control for you. It can automatically detect + if a concurrent modification occurred during user think time. Check for this at + the end of the conversation. </para> </listitem> <listitem> <para> - <emphasis>Detached Objects</emphasis> - If you decide to use the already - discussed <emphasis>session-per-request</emphasis> pattern, all loaded instances - will be in detached state during user think time. Hibernate allows you to - reattach the objects and persist the modifications, the pattern is called + <emphasis>Detached Objects</emphasis>: if you decide to use the + <emphasis>session-per-request</emphasis> pattern, all loaded instances + will be in the detached state during user think time. Hibernate allows you to + reattach the objects and persist the modifications. The pattern is called <emphasis>session-per-request-with-detached-objects</emphasis>. Automatic versioning is used to isolate concurrent modifications. </para> </listitem> <listitem> <para> - <emphasis>Extended (or Long) Session</emphasis> - The Hibernate - <literal>Session</literal> may be disconnected from the underlying JDBC - connection after the database transaction has been committed, and reconnected + <emphasis>Extended (or Long) Session</emphasis>: the Hibernate + <literal>Session</literal> can be disconnected from the underlying JDBC + connection after the database transaction has been committed and reconnected when a new client request occurs. This pattern is known as <emphasis>session-per-conversation</emphasis> and makes even reattachment unnecessary. Automatic versioning is used to isolate - concurrent modifications and the <literal>Session</literal> is usually - not allowed to be flushed automatically, but explicitly. + concurrent modifications and the <literal>Session</literal> will not + be allowed to be flushed automatically, but explicitly. </para> </listitem> </itemizedlist> <para> Both <emphasis>session-per-request-with-detached-objects</emphasis> and - <emphasis>session-per-conversation</emphasis> have advantages and disadvantages, - we discuss them later in this chapter in the context of optimistic concurrency control. + <emphasis>session-per-conversation</emphasis> have advantages and disadvantages. + These disadvantages are discussed later in this chapter in the context of optimistic concurrency control. </para> </sect2> @@ -253,9 +250,9 @@ <title>Considering object identity</title> <para> - An application may concurrently access the same persistent state in two + An application can concurrently access the same persistent state in two different <literal>Session</literal>s. However, an instance of a persistent class - is never shared between two <literal>Session</literal> instances. Hence there are + is never shared between two <literal>Session</literal> instances. It is for this reason that there are two different notions of identity: </para> @@ -279,38 +276,38 @@ </variablelist> <para> - Then for objects attached to a <emphasis>particular</emphasis> <literal>Session</literal> - (i.e. in the scope of a <literal>Session</literal>) the two notions are equivalent, and - JVM identity for database identity is guaranteed by Hibernate. However, while the application + For objects attached to a <emphasis>particular</emphasis> <literal>Session</literal> + (i.e., in the scope of a <literal>Session</literal>), the two notions are equivalent and + JVM identity for database identity is guaranteed by Hibernate. While the application might concurrently access the "same" (persistent identity) business object in two different sessions, the two instances will actually be "different" (JVM identity). Conflicts are - resolved using (automatic versioning) at flush/commit time, using an optimistic approach. + resolved using an optimistic approach and automatic versioning at flush/commit time. </para> <para> - This approach leaves Hibernate and the database to worry about concurrency; it also provides - the best scalability, since guaranteeing identity in single-threaded units of work only doesn't - need expensive locking or other means of synchronization. The application never needs to - synchronize on any business object, as long as it sticks to a single thread per - <literal>Session</literal>. Within a <literal>Session</literal> the application may safely use + This approach leaves Hibernate and the database to worry about concurrency. It also provides + the best scalability, since guaranteeing identity in single-threaded units of work means that it does not + need expensive locking or other means of synchronization. The application does not need to + synchronize on any business object, as long as it maintains a single thread per + <literal>Session</literal>. Within a <literal>Session</literal> the application can safely use <literal>==</literal> to compare objects. </para> <para> - However, an application that uses <literal>==</literal> outside of a <literal>Session</literal>, - might see unexpected results. This might occur even in some unexpected places, for example, - if you put two detached instances into the same <literal>Set</literal>. Both might have the same - database identity (i.e. they represent the same row), but JVM identity is by definition not - guaranteed for instances in detached state. The developer has to override the <literal>equals()</literal> + However, an application that uses <literal>==</literal> outside of a <literal>Session</literal> + might produce unexpected results. This might occur even in some unexpected places. For example, + if you put two detached instances into the same <literal>Set</literal>, both might have the same + database identity (i.e., they represent the same row). JVM identity, however, is by definition not + guaranteed for instances in a detached state. The developer has to override the <literal>equals()</literal> and <literal>hashCode()</literal> methods in persistent classes and implement - his own notion of object equality. There is one caveat: Never use the database - identifier to implement equality, use a business key, a combination of unique, usually + their own notion of object equality. There is one caveat: never use the database + identifier to implement equality. Use a business key that is a combination of unique, usually immutable, attributes. The database identifier will change if a transient object is made persistent. If the transient instance (usually together with detached instances) is held in a <literal>Set</literal>, changing the hashcode breaks the contract of the <literal>Set</literal>. - Attributes for business keys don't have to be as stable as database primary keys, you only + Attributes for business keys do not have to be as stable as database primary keys; you only have to guarantee stability as long as the objects are in the same <literal>Set</literal>. See - the Hibernate website for a more thorough discussion of this issue. Also note that this is not + the Hibernate website for a more thorough discussion of this issue. Please note that this is not a Hibernate issue, but simply how Java object identity and equality has to be implemented. </para> @@ -320,46 +317,46 @@ <title>Common issues</title> <para> - Never use the anti-patterns <emphasis>session-per-user-session</emphasis> or - <emphasis>session-per-application</emphasis> (of course, there are rare exceptions to - this rule). Note that some of the following issues might also appear with the recommended - patterns, make sure you understand the implications before making a design decision: + Do not use the anti-patterns <emphasis>session-per-user-session</emphasis> or + <emphasis>session-per-application</emphasis> (there are, however, rare exceptions to + this rule). Some of the following issues might also arise within the recommended + patterns, so ensure that you understand the implications before making a design decision: </para> <itemizedlist> <listitem> <para> - A <literal>Session</literal> is not thread-safe. Things which are supposed to work + A <literal>Session</literal> is not thread-safe. Things that work concurrently, like HTTP requests, session beans, or Swing workers, will cause race - conditions if a <literal>Session</literal> instance would be shared. If you keep your - Hibernate <literal>Session</literal> in your <literal>HttpSession</literal> (discussed - later), you should consider synchronizing access to your Http session. Otherwise, - a user that clicks reload fast enough may use the same <literal>Session</literal> in + conditions if a <literal>Session</literal> instance is shared. If you keep your + Hibernate <literal>Session</literal> in your <literal>HttpSession</literal> (this is discussed + later in the chapter), you should consider synchronizing access to your Http session. Otherwise, + a user that clicks reload fast enough can use the same <literal>Session</literal> in two concurrently running threads. </para> </listitem> <listitem> <para> An exception thrown by Hibernate means you have to rollback your database transaction - and close the <literal>Session</literal> immediately (discussed later in more detail). + and close the <literal>Session</literal> immediately (this is discussed in more detail later in the chapter). If your <literal>Session</literal> is bound to the application, you have to stop - the application. Rolling back the database transaction doesn't put your business - objects back into the state they were at the start of the transaction. This means the - database state and the business objects do get out of sync. Usually this is not a - problem, because exceptions are not recoverable and you have to start over after + the application. Rolling back the database transaction does not put your business + objects back into the state they were at the start of the transaction. This means that the + database state and the business objects will be out of sync. Usually this is not a + problem, because exceptions are not recoverable and you will have to start over after rollback anyway. </para> </listitem> <listitem> <para> - The <literal>Session</literal> caches every object that is in persistent state (watched - and checked for dirty state by Hibernate). This means it grows endlessly until you - get an OutOfMemoryException, if you keep it open for a long time or simply load too - much data. One solution for this is to call <literal>clear()</literal> and <literal>evict()</literal> - to manage the <literal>Session</literal> cache, but you most likely should consider a + The <literal>Session</literal> caches every object that is in a persistent state (watched + and checked for dirty state by Hibernate). If you keep it open for a long time or simply load too + much data, it will grow endlessly until you + get an OutOfMemoryException. One solution is to call <literal>clear()</literal> and <literal>evict()</literal> + to manage the <literal>Session</literal> cache, but you should consider a Stored Procedure if you need mass data operations. Some solutions are shown in <xref linkend="batch"/>. Keeping a <literal>Session</literal> open for the duration - of a user session also means a high probability of stale data. + of a user session also means a higher probability of stale data. </para> </listitem> </itemizedlist> @@ -372,36 +369,36 @@ <title>Database transaction demarcation</title> <para> - Database (or system) transaction boundaries are always necessary. No communication with + Database, or system, transaction boundaries are always necessary. No communication with the database can occur outside of a database transaction (this seems to confuse many developers who are used to the auto-commit mode). Always use clear transaction boundaries, even for read-only operations. Depending on your isolation level and database capabilities this might not - be required but there is no downside if you always demarcate transactions explicitly. Certainly, + be required, but there is no downside if you always demarcate transactions explicitly. Certainly, a single database transaction is going to perform better than many small transactions, even for reading data. </para> <para> - A Hibernate application can run in non-managed (i.e. standalone, simple Web- or Swing applications) + A Hibernate application can run in non-managed (i.e., standalone, simple Web- or Swing applications) and managed J2EE environments. In a non-managed environment, Hibernate is usually responsible for its own database connection pool. The application developer has to manually set transaction - boundaries, in other words, begin, commit, or rollback database transactions himself. A managed environment + boundaries (begin, commit, or rollback database transactions) themselves. A managed environment usually provides container-managed transactions (CMT), with the transaction assembly defined declaratively - in deployment descriptors of EJB session beans, for example. Programmatic transaction demarcation is + (in deployment descriptors of EJB session beans, for example). Programmatic transaction demarcation is then no longer necessary. </para> <para> However, it is often desirable to keep your persistence layer portable between non-managed resource-local environments, and systems that can rely on JTA but use BMT instead of CMT. - In both cases you'd use programmatic transaction demarcation. Hibernate offers a wrapper + In both cases use programmatic transaction demarcation. Hibernate offers a wrapper API called <literal>Transaction</literal> that translates into the native transaction system of your deployment environment. This API is actually optional, but we strongly encourage its use unless you are in a CMT session bean. </para> <para> - Usually, ending a <literal>Session</literal> involves four distinct phases: + Ending a <literal>Session</literal> usually involves four distinct phases: </para> <itemizedlist spacing="compact"> @@ -428,8 +425,8 @@ </itemizedlist> <para> - Flushing the session has been discussed earlier, we'll now have a closer look at transaction - demarcation and exception handling in both managed- and non-managed environments. + We discussed Flushing the session earlier, so we will now have a closer look at transaction + demarcation and exception handling in both managed and non-managed environments. </para> @@ -438,7 +435,7 @@ <para> If a Hibernate persistence layer runs in a non-managed environment, database connections - are usually handled by simple (i.e. non-DataSource) connection pools from which + are usually handled by simple (i.e., non-DataSource) connection pools from which Hibernate obtains connections as needed. The session/transaction handling idiom looks like this: </para> @@ -463,17 +460,17 @@ }]]></programlisting> <para> - You don't have to <literal>flush()</literal> the <literal>Session</literal> explicitly - - the call to <literal>commit()</literal> automatically triggers the synchronization (depending - upon the <link linkend="objectstate-flushing">FlushMode</link> for the session. + You do not have to <literal>flush()</literal> the <literal>Session</literal> explicitly: + the call to <literal>commit()</literal> automatically triggers the synchronization depending + on the <link linkend="objectstate-flushing">FlushMode</link> for the session. A call to <literal>close()</literal> marks the end of a session. The main implication of <literal>close()</literal> is that the JDBC connection will be relinquished by the session. This Java code is portable and runs in both non-managed and JTA environments. </para> <para> - A much more flexible solution is Hibernate's built-in "current session" context - management, as described earlier: + As outlined earlier, a much more flexible solution is Hibernate's built-in "current session" context + management: </para> <programlisting><![CDATA[// Non-managed environment idiom with getCurrentSession() @@ -491,18 +488,18 @@ }]]></programlisting> <para> - You will very likely never see these code snippets in a regular application; + You will not see these code snippets in a regular application; fatal (system) exceptions should always be caught at the "top". In other words, the - code that executes Hibernate calls (in the persistence layer) and the code that handles - <literal>RuntimeException</literal> (and usually can only clean up and exit) are in + code that executes Hibernate calls in the persistence layer, and the code that handles + <literal>RuntimeException</literal> (and usually can only clean up and exit), are in different layers. The current context management by Hibernate can significantly - simplify this design, as all you need is access to a <literal>SessionFactory</literal>. + simplify this design by accessing a <literal>SessionFactory</literal>. Exception handling is discussed later in this chapter. </para> <para> - Note that you should select <literal>org.hibernate.transaction.JDBCTransactionFactory</literal> - (which is the default), and for the second example <literal>"thread"</literal> as your + You should select <literal>org.hibernate.transaction.JDBCTransactionFactory</literal>, + which is the default, and for the second example select <literal>"thread"</literal> as your <literal>hibernate.current_session_context_class</literal>. </para> @@ -512,15 +509,15 @@ <title>Using JTA</title> <para> - If your persistence layer runs in an application server (e.g. behind EJB session beans), + If your persistence layer runs in an application server (for example, behind EJB session beans), every datasource connection obtained by Hibernate will automatically be part of the global JTA transaction. You can also install a standalone JTA implementation and use it without EJB. Hibernate offers two strategies for JTA integration. </para> <para> - If you use bean-managed transactions (BMT) Hibernate will tell the application server to start - and end a BMT transaction if you use the <literal>Transaction</literal> API. So, the + If you use bean-managed transactions (BMT), Hibernate will tell the application server to start + and end a BMT transaction if you use the <literal>Transaction</literal> API. The transaction management code is identical to the non-managed environment. </para> @@ -546,7 +543,7 @@ <para> If you want to use a transaction-bound <literal>Session</literal>, that is, the <literal>getCurrentSession()</literal> functionality for easy context propagation, - you will have to use the JTA <literal>UserTransaction</literal> API directly: + use the JTA <literal>UserTransaction</literal> API directly: </para> <programlisting><![CDATA[// BMT idiom with getCurrentSession() @@ -568,8 +565,8 @@ }]]></programlisting> <para> - With CMT, transaction demarcation is done in session bean deployment descriptors, not programmatically, - hence, the code is reduced to: + With CMT, transaction demarcation is completed in session bean deployment descriptors, not programmatically. + The code is reduced to: </para> <programlisting><![CDATA[// CMT idiom @@ -580,33 +577,33 @@ ]]></programlisting> <para> - In a CMT/EJB even rollback happens automatically, since an unhandled <literal>RuntimeException</literal> + In a CMT/EJB, even rollback happens automatically. An unhandled <literal>RuntimeException</literal> thrown by a session bean method tells the container to set the global transaction to rollback. - <emphasis>This means you do not need to use the Hibernate <literal>Transaction</literal> API at + <emphasis>You do not need to use the Hibernate <literal>Transaction</literal> API at all with BMT or CMT, and you get automatic propagation of the "current" Session bound to the transaction.</emphasis> </para> <para> - Note that you should choose <literal>org.hibernate.transaction.JTATransactionFactory</literal> + When configuring Hibernate's transaction factory, choose <literal>org.hibernate.transaction.JTATransactionFactory</literal> if you use JTA directly (BMT), and <literal>org.hibernate.transaction.CMTTransactionFactory</literal> - in a CMT session bean, when you configure Hibernate's transaction factory. Remember to also set - <literal>hibernate.transaction.manager_lookup_class</literal>. Furthermore, make sure + in a CMT session bean. Remember to also set + <literal>hibernate.transaction.manager_lookup_class</literal>. Ensure that your <literal>hibernate.current_session_context_class</literal> is either unset (backwards - compatibility), or set to <literal>"jta"</literal>. + compatibility), or is set to <literal>"jta"</literal>. </para> <para> The <literal>getCurrentSession()</literal> operation has one downside in a JTA environment. There is one caveat to the use of <literal>after_statement</literal> connection release - mode, which is then used by default. Due to a silly limitation of the JTA spec, it is not + mode, which is then used by default. Due to a limitation of the JTA spec, it is not possible for Hibernate to automatically clean up any unclosed <literal>ScrollableResults</literal> or <literal>Iterator</literal> instances returned by <literal>scroll()</literal> or <literal>iterate()</literal>. You <emphasis>must</emphasis> release the underlying database cursor by calling <literal>ScrollableResults.close()</literal> or <literal>Hibernate.close(Iterator)</literal> explicitly from a <literal>finally</literal> - block. (Of course, most applications can easily avoid using <literal>scroll()</literal> or - <literal>iterate()</literal> at all from the JTA or CMT code.) + block. Most applications can easily avoid using <literal>scroll()</literal> or + <literal>iterate()</literal> from the JTA or CMT code.) </para> </sect2> @@ -615,8 +612,8 @@ <title>Exception handling</title> <para> - If the <literal>Session</literal> throws an exception (including any - <literal>SQLException</literal>), you should immediately rollback the database + If the <literal>Session</literal> throws an exception, including any + <literal>SQLException</literal>, immediately rollback the database transaction, call <literal>Session.close()</literal> and discard the <literal>Session</literal> instance. Certain methods of <literal>Session</literal> will <emphasis>not</emphasis> leave the session in a consistent state. No @@ -627,14 +624,14 @@ <para> The <literal>HibernateException</literal>, which wraps most of the errors that - can occur in a Hibernate persistence layer, is an unchecked exception (it wasn't - in older versions of Hibernate). In our opinion, we shouldn't force the application + can occur in a Hibernate persistence layer, is an unchecked exception. It was not + in older versions of Hibernate. In our opinion, we should not force the application developer to catch an unrecoverable exception at a low layer. In most systems, unchecked and fatal exceptions are handled in one of the first frames of the method call - stack (i.e. in higher layers) and an error message is presented to the application - user (or some other appropriate action is taken). Note that Hibernate might also throw - other unchecked exceptions which are not a <literal>HibernateException</literal>. These - are, again, not recoverable and appropriate action should be taken. + stack (i.e., in higher layers) and either an error message is presented to the application + user or some other appropriate action is taken. Note that Hibernate might also throw + other unchecked exceptions that are not a <literal>HibernateException</literal>. These + are not recoverable and appropriate action should be taken. </para> <para> @@ -645,40 +642,40 @@ Hibernate converts the <literal>SQLException</literal> into an appropriate <literal>JDBCException</literal> subclass using the <literal>SQLExceptionConverter</literal> attached to the <literal>SessionFactory</literal>. By default, the - <literal>SQLExceptionConverter</literal> is defined by the configured dialect; however, it is - also possible to plug in a custom implementation (see the javadocs for the - <literal>SQLExceptionConverterFactory</literal> class for details). The standard + <literal>SQLExceptionConverter</literal> is defined by the configured dialect. However, it is + also possible to plug in a custom implementation. See the javadocs for the + <literal>SQLExceptionConverterFactory</literal> class for details. The standard <literal>JDBCException</literal> subtypes are: </para> <itemizedlist spacing="compact"> <listitem> <para> - <literal>JDBCConnectionException</literal> - indicates an error + <literal>JDBCConnectionException</literal>: indicates an error with the underlying JDBC communication. </para> </listitem> <listitem> <para> - <literal>SQLGrammarException</literal> - indicates a grammar + <literal>SQLGrammarException</literal>: indicates a grammar or syntax problem with the issued SQL. </para> </listitem> <listitem> <para> - <literal>ConstraintViolationException</literal> - indicates some + <literal>ConstraintViolationException</literal>: indicates some form of integrity constraint violation. </para> </listitem> <listitem> <para> - <literal>LockAcquisitionException</literal> - indicates an error + <literal>LockAcquisitionException</literal>: indicates an error acquiring a lock level necessary to perform the requested operation. </para> </listitem> <listitem> <para> - <literal>GenericJDBCException</literal> - a generic exception + <literal>GenericJDBCException</literal>: a generic exception which did not fall into any of the other categories. </para> </listitem> @@ -690,8 +687,8 @@ <title>Transaction timeout</title> <para> - One extremely important feature provided by a managed environment like EJB - that is never provided for non-managed code is transaction timeout. Transaction + An important feature provided by a managed environment like EJB, + that is never provided for non-managed code, is transaction timeout. Transaction timeouts ensure that no misbehaving transaction can indefinitely tie up resources while returning no response to the user. Outside a managed (JTA) environment, Hibernate cannot fully provide this functionality. However, @@ -723,7 +720,7 @@ }]]></programlisting> <para> - Note that <literal>setTimeout()</literal> may not be called in a CMT bean, + <literal>setTimeout()</literal> cannot be called in a CMT bean, where transaction timeouts must be defined declaratively. </para> @@ -736,11 +733,11 @@ <para> The only approach that is consistent with high concurrency and high - scalability is optimistic concurrency control with versioning. Version + scalability, is optimistic concurrency control with versioning. Version checking uses version numbers, or timestamps, to detect conflicting updates - (and to prevent lost updates). Hibernate provides for three possible approaches + and to prevent lost updates. Hibernate provides three possible approaches to writing application code that uses optimistic concurrency. The use cases - we show are in the context of long conversations, but version checking + we discuss are in the context of long conversations, but version checking also has the benefit of preventing lost updates in single database transactions. </para> @@ -751,7 +748,7 @@ In an implementation without much help from Hibernate, each interaction with the database occurs in a new <literal>Session</literal> and the developer is responsible for reloading all persistent instances from the database before manipulating them. - This approach forces the application to carry out its own version checking to ensure + The application is forced to carry out its own version checking to ensure conversation transaction isolation. This approach is the least efficient in terms of database access. It is the approach most similar to entity EJBs. </para> @@ -775,18 +772,18 @@ </para> <para> - Of course, if you are operating in a low-data-concurrency environment and don't - require version checking, you may use this approach and just skip the version - check. In that case, <emphasis>last commit wins</emphasis> will be the default - strategy for your long conversations. Keep in mind that this might + If you are operating in a low-data-concurrency environment, and do not + require version checking, you can use this approach and skip the version + check. In this case, <emphasis>last commit wins</emphasis> is the default + strategy for long conversations. Be aware that this might confuse the users of the application, as they might experience lost updates without error messages or a chance to merge conflicting changes. </para> <para> - Clearly, manual version checking is only feasible in very trivial circumstances + Manual version checking is only feasible in trivial circumstances and not practical for most applications. Often not only single instances, but - complete graphs of modified objects have to be checked. Hibernate offers automatic + complete graphs of modified objects, have to be checked. Hibernate offers automatic version checking with either an extended <literal>Session</literal> or detached instances as the design paradigm. </para> @@ -797,19 +794,19 @@ <title>Extended session and automatic versioning</title> <para> - A single <literal>Session</literal> instance and its persistent instances are - used for the whole conversation, known as <emphasis>session-per-conversation</emphasis>. + A single <literal>Session</literal> instance and its persistent instances that are + used for the whole conversation are known as <emphasis>session-per-conversation</emphasis>. Hibernate checks instance versions at flush time, throwing an exception if concurrent - modification is detected. It's up to the developer to catch and handle this exception - (common options are the opportunity for the user to merge changes or to restart the - business conversation with non-stale data). + modification is detected. It is up to the developer to catch and handle this exception. + Common options are the opportunity for the user to merge changes or to restart the + business conversation with non-stale data. </para> <para> The <literal>Session</literal> is disconnected from any underlying JDBC connection when waiting for user interaction. This approach is the most efficient in terms - of database access. The application need not concern itself with version checking or - with reattaching detached instances, nor does it have to reload instances in every + of database access. The application does not version check or + reattach detached instances, nor does it have to reload instances in every database transaction. </para> @@ -822,41 +819,43 @@ t.commit(); // Also return JDBC connection session.close(); // Only for last transaction in conversation]]></programlisting> <para> - The <literal>foo</literal> object still knows which <literal>Session</literal> it was + The <literal>foo</literal> object knows which <literal>Session</literal> it was loaded in. Beginning a new database transaction on an old session obtains a new connection and resumes the session. Committing a database transaction disconnects a session from the JDBC connection and returns the connection to the pool. After reconnection, to - force a version check on data you aren't updating, you may call <literal>Session.lock()</literal> + force a version check on data you are not updating, you can call <literal>Session.lock()</literal> with <literal>LockMode.READ</literal> on any objects that might have been updated by another - transaction. You don't need to lock any data that you <emphasis>are</emphasis> updating. + transaction. You do not need to lock any data that you <emphasis>are</emphasis> updating. Usually you would set <literal>FlushMode.MANUAL</literal> on an extended <literal>Session</literal>, so that only the last database transaction cycle is allowed to actually persist all - modifications made in this conversation. Hence, only this last database transaction - would include the <literal>flush()</literal> operation, and then also + modifications made in this conversation. Only this last database transaction + will include the <literal>flush()</literal> operation, and then <literal>close()</literal> the session to end the conversation. </para> <para> This pattern is problematic if the <literal>Session</literal> is too big to - be stored during user think time, e.g. an <literal>HttpSession</literal> should - be kept as small as possible. As the <literal>Session</literal> is also the - (mandatory) first-level cache and contains all loaded objects, we can probably - use this strategy only for a few request/response cycles. You should use a - <literal>Session</literal> only for a single conversation, as it will soon also + be stored during user think time (for example, an <literal>HttpSession</literal> should + be kept as small as possible). As the <literal>Session</literal> is also the + first-level cache and contains all loaded objects, we can probably + use this strategy only for a few request/response cycles. Use a + <literal>Session</literal> only for a single conversation as it will soon have stale data. </para> - <para> - (Note that earlier Hibernate versions required explicit disconnection and reconnection + <note> + <title>Note</title> + <para>Earlier versions of Hibernate required explicit disconnection and reconnection of a <literal>Session</literal>. These methods are deprecated, as beginning and - ending a transaction has the same effect.) - </para> + ending a transaction has the same effect. + </para> + </note> <para> - Also note that you should keep the disconnected <literal>Session</literal> close - to the persistence layer. In other words, use an EJB stateful session bean to - hold the <literal>Session</literal> in a three-tier environment, and don't transfer - it to the web layer (or even serialize it to a separate tier) to store it in the + Keep the disconnected <literal>Session</literal> close + to the persistence layer. Use an EJB stateful session bean to + hold the <literal>Session</literal> in a three-tier environment. Do not transfer + it to the web layer, or even serialize it to a separate tier, to store it in the <literal>HttpSession</literal>. </para> @@ -864,7 +863,7 @@ The extended session pattern, or <emphasis>session-per-conversation</emphasis>, is more difficult to implement with automatic current session context management. You need to supply your own implementation of the <literal>CurrentSessionContext</literal> - for this, see the Hibernate Wiki for examples. + for this. See the Hibernate Wiki for examples. </para> </sect2> @@ -894,8 +893,8 @@ </para> <para> - You may also call <literal>lock()</literal> instead of <literal>update()</literal> - and use <literal>LockMode.READ</literal> (performing a version check, bypassing all + You can also call <literal>lock()</literal> instead of <literal>update()</literal>, + and use <literal>LockMode.READ</literal> (performing a version check and bypassing all caches) if you are sure that the object has not been modified. </para> @@ -905,40 +904,41 @@ <title>Customizing automatic versioning</title> <para> - You may disable Hibernate's automatic version increment for particular properties and + You can disable Hibernate's automatic version increment for particular properties and collections by setting the <literal>optimistic-lock</literal> mapping attribute to <literal>false</literal>. Hibernate will then no longer increment versions if the property is dirty. </para> <para> - Legacy database schemas are often static and can't be modified. Or, other applications - might also access the same database and don't know how to handle version numbers or - even timestamps. In both cases, versioning can't rely on a particular column in a table. - To force a version check without a version or timestamp property mapping, with a - comparison of the state of all fields in a row, turn on <literal>optimistic-lock="all"</literal> - in the <literal>&lt;class&gt;</literal> mapping. Note that this conceptually only works - if Hibernate can compare the old and new state, i.e. if you use a single long - <literal>Session</literal> and not session-per-request-with-detached-objects. + Legacy database schemas are often static and cannot be modified. Or, other applications + might access the same database and will not know how to handle version numbers or + even timestamps. In both cases, versioning cannot rely on a particular column in a table. + To force a version check with a + comparison of the state of all fields in a row but without a version or timestamp property mapping, + turn on <literal>optimistic-lock="all"</literal> + in the <literal>&lt;class&gt;</literal> mapping. This conceptually only works + if Hibernate can compare the old and the new state (i.e., if you use a single long + <literal>Session</literal> and not session-per-request-with-detached-objects). </para> <para> - Sometimes concurrent modification can be permitted as long as the changes that have been - made don't overlap. If you set <literal>optimistic-lock="dirty"</literal> when mapping the + Concurrent modification can be permitted in instances where the changes that have been + made do not overlap. If you set <literal>optimistic-lock="dirty"</literal> when mapping the <literal>&lt;class&gt;</literal>, Hibernate will only compare dirty fields during flush. </para> <para> - In both cases, with dedicated version/timestamp columns or with full/dirty field - comparison, Hibernate uses a single <literal>UPDATE</literal> statement (with an - appropriate <literal>WHERE</literal> clause) per entity to execute the version check + In both cases, with dedicated version/timestamp columns or with a full/dirty field + comparison, Hibernate uses a single <literal>UPDATE</literal> statement, with an + appropriate <literal>WHERE</literal> clause, per entity to execute the version check and update the information. If you use transitive persistence to cascade reattachment - to associated entities, Hibernate might execute unnecessary updates. This is usually + to associated entities, Hibernate may execute unnecessary updates. This is usually not a problem, but <emphasis>on update</emphasis> triggers in the database might be executed even when no changes have been made to detached instances. You can customize this behavior by setting <literal>select-before-update="true"</literal> in the <literal>&lt;class&gt;</literal> mapping, forcing Hibernate to <literal>SELECT</literal> - the instance to ensure that changes did actually occur, before updating the row. + the instance to ensure that changes did occur before updating the row. </para> </sect2> @@ -946,22 +946,22 @@ </sect1> <sect1 id="transactions-locking"> - <title>Pessimistic Locking</title> + <title>Pessimistic locking</title> <para> - It is not intended that users spend much time worrying about locking strategies. It's usually + It is not intended that users spend much time worrying about locking strategies. It is usually enough to specify an isolation level for the JDBC connections and then simply let the - database do all the work. However, advanced users may sometimes wish to obtain - exclusive pessimistic locks, or re-obtain locks at the start of a new transaction. + database do all the work. However, advanced users may wish to obtain + exclusive pessimistic locks or re-obtain locks at the start of a new transaction. </para> <para> - Hibernate will always use the locking mechanism of the database, never lock objects - in memory! + Hibernate will always use the locking mechanism of the database; it never lock objects + in memory. </para> <para> - The <literal>LockMode</literal> class defines the different lock levels that may be acquired + The <literal>LockMode</literal> class defines the different lock levels that can be acquired by Hibernate. A lock is obtained by the following mechanisms: </para> @@ -974,20 +974,20 @@ </listitem> <listitem> <para> - <literal>LockMode.UPGRADE</literal> may be acquired upon explicit user request using + <literal>LockMode.UPGRADE</literal> can be acquired upon explicit user request using <literal>SELECT ... FOR UPDATE</literal> on databases which support that syntax. </para> </listitem> <listitem> <para> - <literal>LockMode.UPGRADE_NOWAIT</literal> may be acquired upon explicit user request using a + <literal>LockMode.UPGRADE_NOWAIT</literal> can be acquired upon explicit user request using a <literal>SELECT ... FOR UPDATE NOWAIT</literal> under Oracle. </para> </listitem> <listitem> <para> <literal>LockMode.READ</literal> is acquired automatically when Hibernate reads data - under Repeatable Read or Serializable isolation level. May be re-acquired by explicit user + under Repeatable Read or Serializable isolation level. It can be re-acquired by explicit user request. </para> </listitem> @@ -1035,29 +1035,29 @@ <para> <literal>Session.lock()</literal> performs a version number check if the specified lock mode is <literal>READ</literal>, <literal>UPGRADE</literal> or - <literal>UPGRADE_NOWAIT</literal>. (In the case of <literal>UPGRADE</literal> or - <literal>UPGRADE_NOWAIT</literal>, <literal>SELECT ... FOR UPDATE</literal> is used.) + <literal>UPGRADE_NOWAIT</literal>. In the case of <literal>UPGRADE</literal> or + <literal>UPGRADE_NOWAIT</literal>, <literal>SELECT ... FOR UPDATE</literal> is used. </para> <para> - If the database does not support the requested lock mode, Hibernate will use an appropriate - alternate mode (instead of throwing an exception). This ensures that applications will - be portable. + If the requested lock mode is not supported by the database, Hibernate uses an appropriate + alternate mode instead of throwing an exception. This ensures that applications are + portable. </para> </sect1> <sect1 id="transactions-connection-release"> - <title>Connection Release Modes</title> + <title>Connection release modes</title> <para> - The legacy (2.x) behavior of Hibernate in regards to JDBC connection management - was that a <literal>Session</literal> would obtain a connection when it was first - needed and then hold unto that connection until the session was closed. - Hibernate 3.x introduced the notion of connection release modes to tell a session - how to handle its JDBC connections. Note that the following discussion is pertinent - only to connections provided through a configured <literal>ConnectionProvider</literal>; - user-supplied connections are outside the breadth of this discussion. The different + One of the legacies of Hibernate 2.x JDBC connection management + meant that a <literal>Session</literal> would obtain a connection when it was first + required and then maintain that connection until the session was closed. + Hibernate 3.x introduced the notion of connection release modes that would instruct a session + how to handle its JDBC connections. The following discussion is pertinent + only to connections provided through a configured <literal>ConnectionProvider</literal>. + User-supplied connections are outside the breadth of this discussion. The different release modes are identified by the enumerated values of <literal>org.hibernate.ConnectionReleaseMode</literal>: </para> @@ -1065,23 +1065,23 @@ <itemizedlist spacing="compact"> <listitem> <para> - <literal>ON_CLOSE</literal> - is essentially the legacy behavior described above. The + <literal>ON_CLOSE</literal>: is the legacy behavior described above. The Hibernate session obtains a connection when it first needs to perform some JDBC access - and holds unto that connection until the session is closed. + and maintains that connection until the session is closed. </para> </listitem> <listitem> <para> - <literal>AFTER_TRANSACTION</literal> - says to release connections after a - <literal>org.hibernate.Transaction</literal> has completed. + <literal>AFTER_TRANSACTION</literal>: releases connections after a + <literal>org.hibernate.Transaction</literal> has been completed. </para> </listitem> <listitem> <para> - <literal>AFTER_STATEMENT</literal> (also referred to as aggressive release) - says to - release connections after each and every statement execution. This aggressive releasing - is skipped if that statement leaves open resources associated with the given session; - currently the only situation where this occurs is through the use of + <literal>AFTER_STATEMENT</literal> (also referred to as aggressive release): + releases connections after every statement execution. This aggressive releasing + is skipped if that statement leaves open resources associated with the given session. + Currently the only situation where this occurs is through the use of <literal>org.hibernate.ScrollableResults</literal>. </para> </listitem> @@ -1089,43 +1089,43 @@ <para> The configuration parameter <literal>hibernate.connection.release_mode</literal> is used - to specify which release mode to use. The possible values: + to specify which release mode to use. The possible values are as follows: </para> <itemizedlist spacing="compact"> <listitem> <para> - <literal>auto</literal> (the default) - this choice delegates to the release mode + <literal>auto</literal> (the default): this choice delegates to the release mode returned by the <literal>org.hibernate.transaction.TransactionFactory.getDefaultReleaseMode()</literal> method. For JTATransactionFactory, this returns ConnectionReleaseMode.AFTER_STATEMENT; for - JDBCTransactionFactory, this returns ConnectionReleaseMode.AFTER_TRANSACTION. It is rarely - a good idea to change this default behavior as failures due to the value of this setting + JDBCTransactionFactory, this returns ConnectionReleaseMode.AFTER_TRANSACTION. Do not + change this default behavior as failures due to the value of this setting tend to indicate bugs and/or invalid assumptions in user code. </para> </listitem> <listitem> <para> - <literal>on_close</literal> - says to use ConnectionReleaseMode.ON_CLOSE. This setting - is left for backwards compatibility, but its use is highly discouraged. + <literal>on_close</literal>: uses ConnectionReleaseMode.ON_CLOSE. This setting + is left for backwards compatibility, but its use is discouraged. </para> </listitem> <listitem> <para> - <literal>after_transaction</literal> - says to use ConnectionReleaseMode.AFTER_TRANSACTION. + <literal>after_transaction</literal>: uses ConnectionReleaseMode.AFTER_TRANSACTION. This setting should not be used in JTA environments. Also note that with ConnectionReleaseMode.AFTER_TRANSACTION, if a session is considered to be in auto-commit - mode connections will be released as if the release mode were AFTER_STATEMENT. + mode, connections will be released as if the release mode were AFTER_STATEMENT. </para> </listitem> <listitem> <para> - <literal>after_statement</literal> - says to use ConnectionReleaseMode.AFTER_STATEMENT. Additionally, + <literal>after_statement</literal>: uses ConnectionReleaseMode.AFTER_STATEMENT. Additionally, the configured <literal>ConnectionProvider</literal> is consulted to see if it supports this setting (<literal>supportsAggressiveRelease()</literal>). If not, the release mode is reset to ConnectionReleaseMode.AFTER_TRANSACTION. This setting is only safe in environments where - we can either re-acquire the same underlying JDBC connection each time we make a call into + we can either re-acquire the same underlying JDBC connection each time you make a call into <literal>ConnectionProvider.getConnection()</literal> or in auto-commit environments where - it does not matter whether we get back the same connection. + it does not matter if we re-establish the same connection. </para> </listitem> </itemizedlist> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/tutorial.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/tutorial.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/tutorial.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -27,7 +27,7 @@ <!ENTITY mdash "-"> ]> - <!-- todo : need searate sections, one for each tutorial --> + <!-- todo : need separate sections, one for each tutorial --> <chapter id="tutorial"> <title>Introduction to Hibernate</title> @@ -36,11 +36,10 @@ <title>Preface</title> <para> - This chapter is an introduction to Hibernate by way of a tutorial, - intended for new users of Hibernate. We start with a simple - application using an in-memory database. We build the - application in small, easy to understand steps. The tutorial is - based on another, earlier one developed by Michael Gloegl. All + Intended for new users, this chapter provides an introduction to Hibernate + The chapter provides a step-by-step tutorial, starting with a simple + application using an in-memory database. The tutorial is + based on an earlier tutorial developed by Michael Gloegl. All code is contained in the <filename>tutorials/web</filename> directory of the project source. </para> @@ -50,10 +49,9 @@ <important> <para> This tutorial expects the user have knowledge of both Java and - SQL. If you are new or uncomfortable with either, it is advised + SQL. If you have a limited knowledge of JAVA or SQL, it is advised that you start with a good introduction to that technology prior - to attempting to learn Hibernate. It will save time and effort - in the long run. + to attempting to learn Hibernate. </para> </important> @@ -61,7 +59,7 @@ <para> There is another tutorial/example application in the <filename>/tutorials/eg</filename> directory of the project source. - That example is console based and as such would not have the + That example is console-based and, as such, would not have the dependency on a servlet container to execute. The basic setup is the same as the instructions below. </para> @@ -71,22 +69,21 @@ <title>Part 1 - The first Hibernate Application</title> <para> - Let's assume we need a small database application that can store + For this example, we will set up a small database application that can store events we want to attend, and information about the host(s) of - these events. We will use an in-memory, Java database named HSQLDB + these events. Although you can use whatever database you feel comfortable using, we will use an in-memory, Java database named HSQLDB to avoid describing installation/setup of any particular database - servers. Feel free to tweak this tutorial to use whatever database - you feel comfortable using. + servers. </para> <para> - The first thing we need to do is set up our development environment, - and specifically to setup all the required dependencies to Hibernate - as well as other libraries. Hibernate is built using Maven which - amongst other features provides <literal>dependecy management</literal>; + The first thing we need to do is set up the development environment, + including all the required dependencies to Hibernate, + as well as other libraries. Hibernate is built using Maven which, + amongst other features, provides <literal>dependency management</literal>; moreover it provides <emphasis>transitive</emphasis> - <literal>dependecy management</literal> which simply means that to use - Hibernate we can simply define our dependency on Hibernate, Hibernate + <literal>dependency management</literal>, which simply means that by using + Hibernate we can define our dependency on Hibernate. Hibernate itself defines the dependencies it needs which then become transitive dependencies of our project. </para> @@ -124,20 +121,19 @@ <tip> <para> While not strictly necessary, most IDEs have integration with Maven - to read these POM files and automatically set up a project for you - which can save lots of time and effort. + to read these POM files and automatically set up a project for you. </para> </tip> <para> - Next we create a class that represents the event we want to store in database. + Next, create a class that represents the event you want to store in the database. </para> <sect2 id="tutorial-firstapp-firstclass"> <title>The first class</title> <para> - Our first persistent class is a simple JavaBean class with some properties: + The first persistent class is a simple JavaBean class with some properties: </para> <programlisting><![CDATA[package org.hibernate.tutorial.domain; @@ -178,9 +174,9 @@ }]]></programlisting> <para> - You can see that this class uses standard JavaBean naming conventions for property - getter and setter methods, as well as private visibility for the fields. This is - a recommended design - but not required. Hibernate can also access fields directly, + This class uses standard JavaBean naming conventions for property + getter and setter methods, as well as private visibility for the fields. Although this is + a recommended design, it is not required. Hibernate can also access fields directly, the benefit of accessor methods is robustness for refactoring. The no-argument constructor is required to instantiate an object of this class through reflection. </para> @@ -189,11 +185,11 @@ The <literal>id</literal> property holds a unique identifier value for a particular event. All persistent entity classes (there are less important dependent classes as well) will need such an identifier property if we want to use the full feature set of Hibernate. In fact, - most applications (esp. web applications) need to distinguish objects by identifier, so you - should consider this a feature rather than a limitation. However, we usually don't manipulate + most applications, especially web applications, need to distinguish objects by identifier, so you + should consider this a feature rather than a limitation. However, we usually do not manipulate the identity of an object, hence the setter method should be private. Only Hibernate will assign - identifiers when an object is saved. You can see that Hibernate can access public, private, - and protected accessor methods, as well as (public, private, protected) fields directly. The + identifiers when an object is saved. Hibernate can access public, private, + and protected accessor methods, as well as public, private and protected fields directly. The choice is up to you and you can match it to fit your application design. </para> @@ -205,7 +201,7 @@ </para> <para> - Place this Java source file in a directory called <literal>src</literal> in the + Place the Java source file in a directory called <literal>src</literal> in the development folder, and in its correct package. The directory should now look like this: </para> @@ -246,26 +242,26 @@ </hibernate-mapping>]]></programlisting> <para> - Note that the Hibernate DTD is very sophisticated. You can use it for + Hibernate DTD is sophisticated. You can use it for auto-completion of XML mapping elements and attributes in your editor or - IDE. You also should open up the DTD file in your text editor - it's the - easiest way to get an overview of all elements and attributes and to see - the defaults, as well as some comments. Note that Hibernate will not + IDE. Opening up the DTD file in your text editor is the + easiest way to get an overview of all elements and attributes, and to view + the defaults, as well as some comments. Hibernate will not load the DTD file from the web, but first look it up from the classpath of the application. The DTD file is included in <literal>hibernate3.jar</literal> as well as in the <literal>src/</literal> directory of the Hibernate distribution. </para> <para> - We will omit the DTD declaration in future examples to shorten the code. It is - of course not optional. + We will omit the DTD declaration in future examples to shorten the code. It is, + of course, not optional. </para> <para> Between the two <literal>hibernate-mapping</literal> tags, include a <literal>class</literal> element. All persistent entity classes (again, there might be dependent classes later on, which are not first-class entities) need - such a mapping, to a table in the SQL database: + a mapping to a table in the SQL database: </para> <programlisting><![CDATA[<hibernate-mapping> @@ -277,10 +273,10 @@ </hibernate-mapping>]]></programlisting> <para> - So far we told Hibernate how to persist and load object of class <literal>Event</literal> - to the table <literal>EVENTS</literal>, each instance represented by a row in that table. - Now we continue with a mapping of the unique identifier property to the tables primary key. - In addition, as we don't want to care about handling this identifier, we configure Hibernate's + So far we have told Hibernate how to persist and load object of class <literal>Event</literal> + to the table <literal>EVENTS</literal>. Each instance is now represented by a row in that table. + Now we can continue by mapping the unique identifier property to the tables primary key. + As we do not want to care about handling this identifier, we configure Hibernate's identifier generation strategy for a surrogate primary key column: </para> @@ -296,19 +292,20 @@ <para> The <literal>id</literal> element is the declaration of the identifier property, - <literal>name="id"</literal> declares the name of the Java property - + <literal>name="id"</literal> declares the name of the Java property. Hibernate will use the getter and setter methods to access the property. The column attribute tells Hibernate which column of the - <literal>EVENTS</literal> table we use for this primary key. The nested - <literal>generator</literal> element specifies the identifier generation strategy, - in this case we used <literal>native</literal>, which picks the best strategy depending - on the configured database (dialect). Hibernate supports database generated, globally - unique, as well as application assigned identifiers (or any strategy you have written - an extension for). + <literal>EVENTS</literal> table to use for this primary key. The nested + <literal>generator</literal> element specifies the identifier generation strategy. + + In this case you used <literal>native</literal>, which selects the best strategy depending + on the configured database dialect. Hibernate supports database generated, globally + unique, as well as application assigned, identifiers. Hibernate supports any strategy you have written + an extension for. </para> <para> - Finally we include declarations for the persistent properties of the class in + Finally, include declarations for the persistent properties of the class in the mapping file. By default, no properties of the class are considered persistent: </para> @@ -327,42 +324,42 @@ </hibernate-mapping>]]></programlisting> <para> - Just as with the <literal>id</literal> element, the <literal>name</literal> + Similar to the <literal>id</literal> element, the <literal>name</literal> attribute of the <literal>property</literal> element tells Hibernate which getter - and setter methods to use. So, in this case, Hibernate will look for + and setter methods to use. In this case, Hibernate will search for <literal>getDate()/setDate()</literal>, as well as <literal>getTitle()/setTitle()</literal>. </para> <para> Why does the <literal>date</literal> property mapping include the <literal>column</literal> attribute, but the <literal>title</literal> - doesn't? Without the <literal>column</literal> attribute Hibernate - by default uses the property name as the column name. This works fine for - <literal>title</literal>. However, <literal>date</literal> is a reserved - keyword in most database, so we better map it to a different name. + does not? Without the <literal>column</literal> attribute, Hibernate + by default uses the property name as the column name. This works for + <literal>title</literal>, however, <literal>date</literal> is a reserved + keyword in most databases so you will need to map it to a different name. </para> <para> - The next interesting thing is that the <literal>title</literal> mapping also lacks - a <literal>type</literal> attribute. The types we declare and use in the mapping + The <literal>title</literal> mapping also lacks + a <literal>type</literal> attribute. The types declared and used in the mapping files are not, as you might expect, Java data types. They are also not SQL - database types. These types are so called <emphasis>Hibernate mapping types</emphasis>, + database types. These types are called <emphasis>Hibernate mapping types</emphasis>, converters which can translate from Java to SQL data types and vice versa. Again, Hibernate will try to determine the correct conversion and mapping type itself if the <literal>type</literal> attribute is not present in the mapping. In some cases this - automatic detection (using Reflection on the Java class) might not have the default you - expect or need. This is the case with the <literal>date</literal> property. Hibernate can't - know if the property (which is of <literal>java.util.Date</literal>) should map to a + automatic detection using Reflection on the Java class might not have the default you + expect or need. This is the case with the <literal>date</literal> property. Hibernate cannot + know if the property, which is of <literal>java.util.Date</literal>, should map to a SQL <literal>date</literal>, <literal>timestamp</literal>, or <literal>time</literal> column. - We preserve full date and time information by mapping the property with a + Full date and time information is preserved by mapping the property with a <literal>timestamp</literal> converter. </para> <para> - This mapping file should be saved as <literal>Event.hbm.xml</literal>, right in + Save the mapping file as <literal>Event.hbm.xml</literal> in the directory next to the <literal>Event</literal> Java class source file. - The naming of mapping files can be arbitrary, however the <literal>hbm.xml</literal> - suffix is a convention in the Hibernate developer community. The directory structure + The naming of mapping files can be arbitrary, however, the <literal>hbm.xml</literal> + suffix is a convention in the Hibernate developer community. The directory structure should now look like this: </para> @@ -375,7 +372,7 @@ Event.hbm.xml]]></programlisting> <para> - We continue with the main configuration of Hibernate. + The next section continues with the main configuration of Hibernate. </para> </sect2> @@ -384,36 +381,36 @@ <title>Hibernate configuration</title> <para> - We now have a persistent class and its mapping file in place. It is time to configure - Hibernate. Before we do this, we will need a database. HSQL DB, a java-based SQL DBMS, - can be downloaded from the HSQL DB website(http://hsqldb.org/). Actually, you only need the <literal>hsqldb.jar</literal> + You should have a persistent class and its mapping file in place. It is now time to configure + Hibernate. Before you do this, you will need a database. HSQL DB, a java-based SQL DBMS, + can be downloaded from the HSQL DB website(http://hsqldb.org/). You only need the <literal>hsqldb.jar</literal> from this download. Place this file in the <literal>lib/</literal> directory of the development folder. </para> <para> - Create a directory called <literal>data</literal> in the root of the development directory - - this is where HSQL DB will store its data files. Now start the database by running + Create a directory called <literal>data</literal> in the root of the development directory. + This is where HSQL DB will store its data files. Start the database by running <literal>java -classpath ../lib/hsqldb.jar org.hsqldb.Server</literal> in this data directory. - You can see it start up and bind to a TCP/IP socket, this is where our application + You will see it start up and bind to a TCP/IP socket; this is where our application will connect later. If you want to start with a fresh database during this tutorial, shutdown HSQL DB (press <literal>CTRL + C</literal> in the window), delete all files in the <literal>data/</literal> directory, and start HSQL DB again. </para> <para> - Hibernate is the layer in your application which connects to this database, so it needs - connection information. The connections are made through a JDBC connection pool, which we - also have to configure. The Hibernate distribution contains several open source JDBC connection - pooling tools, but will use the Hibernate built-in connection pool for this tutorial. Note that - you have to copy the required library into your classpath and use different + Hibernate is the layer in your application that connects to this database, so it needs + connection information. The connections are made through a JDBC connection pool, which you + will also have to configure. The Hibernate distribution contains several open source JDBC connection + pooling tools, but you will use the Hibernate built-in connection pool for this tutorial. + You will have to copy the required library into your classpath and use different connection pooling settings if you want to use a production-quality third party JDBC pooling software. </para> <para> For Hibernate's configuration, we can use a simple <literal>hibernate.properties</literal> file, a - slightly more sophisticated <literal>hibernate.cfg.xml</literal> file, or even complete + more sophisticated <literal>hibernate.cfg.xml</literal> file, or even complete programmatic setup. Most users prefer the XML configuration file: </para> @@ -457,30 +454,30 @@ </hibernate-configuration>]]></programlisting> <para> - Note that this XML configuration uses a different DTD. We configure - Hibernate's <literal>SessionFactory</literal> - a global factory responsible - for a particular database. If you have several databases, use several - <literal>&lt;session-factory&gt;</literal> configurations, usually in - several configuration files (for easier startup). + This XML configuration uses a different DTD. You configure + Hibernate's <literal>SessionFactory</literal>. SessionFactory is a global factory responsible + for a particular database. If you have several databases, for easier startup you should use several + <literal>&lt;session-factory&gt;</literal> configurations in + several configuration files. </para> <para> The first four <literal>property</literal> elements contain the necessary configuration for the JDBC connection. The dialect <literal>property</literal> element specifies the particular SQL variant Hibernate generates. - Hibernate's automatic session management for persistence contexts will - come in handy as you will soon see. + Hibernate's automatic session management for persistence contexts is particularly useful in this context. + The <literal>hbm2ddl.auto</literal> option turns on automatic generation of - database schemas - directly into the database. This can of course also be turned - off (by removing the config option) or redirected to a file with the help of - the <literal>SchemaExport</literal> Ant task. Finally, we add the mapping file(s) + database schemas directly into the database. This can also be turned + off by removing the configuration option, or redirected to a file with the help of + the <literal>SchemaExport</literal> Ant task. Finally, add the mapping file(s) for persistent classes to the configuration. </para> <para> - Copy this file into the source directory, so it will end up in the - root of the classpath. Hibernate automatically looks for a file called - <literal>hibernate.cfg.xml</literal> in the root of the classpath, on startup. + Copy the file into the source directory, so it will end up in the + root of the classpath. On startup, Hibernate automatically searches for a file called + <literal>hibernate.cfg.xml</literal> in the root of the classpath. </para> </sect2> @@ -489,11 +486,11 @@ <title>Building with Ant</title> <para> - We'll now build the tutorial with Ant. You will need to have Ant installed - get - it from the <ulink url="http://ant.apache.org/bindownload.cgi">Ant download page</ulink>. - How to install Ant will not be covered here. Please refer to the - <ulink url="http://ant.apache.org/manual/index.html">Ant manual</ulink>. After you - have installed Ant, we can start to create the buildfile. It will be called + We will now build the tutorial with Ant. You will need to have Ant installed. + It is available from the <ulink url="http://ant.apache.org/bindownload.cgi">Ant download page</ulink>. + Installation instructions for Ant, however, are not be covered here. Please refer to the + <ulink url="http://ant.apache.org/manual/index.html">Ant manual</ulink> for further information. After you + have installed Ant, you can start to create the buildfile. It will be called <literal>build.xml</literal> and placed directly in the development directory. </para> @@ -535,10 +532,10 @@ </project>]]></programlisting> <para> - This will tell Ant to add all files in the lib directory ending with <literal>.jar</literal> + This will tell Ant to add all files in the library directory ending with <literal>.jar</literal> to the classpath used for compilation. It will also copy all non-Java source files to the - target directory, e.g. configuration and Hibernate mapping files. If you now run Ant, you - should get this output: + target directory, configuration and Hibernate mapping files, for example. If you now run Ant, you + will get this output: </para> <programlisting><![CDATA[C:\hibernateTutorial\>ant @@ -559,19 +556,19 @@ <title>Startup and helpers</title> <para> - It's time to load and store some <literal>Event</literal> objects, but first - we have to complete the setup with some infrastructure code. We have to startup - Hibernate. This startup includes building a global <literal>SessionFactory</literal> - object and to store it somewhere for easy access in application code. - A <literal>SessionFactory</literal> can open up new <literal>Session</literal>'s. - A <literal>Session</literal> represents a single-threaded unit of work, the - <literal>SessionFactory</literal> is a thread-safe global object, instantiated once. + It is time to load and store some <literal>Event</literal> objects, but first + you have to complete the setup with some infrastructure code. You have to startup + Hibernate by building a global <literal>SessionFactory</literal> + object and storing it somewhere for easy access in application code. + A <literal>SessionFactory</literal> can open up new <literal>Session</literal>s. + A <literal>Session</literal> represents a single-threaded unit of work. The + <literal>SessionFactory</literal> is a thread-safe global object, that is instantiated once. </para> <para> - We'll create a <literal>HibernateUtil</literal> helper class which takes care + Create a <literal>HibernateUtil</literal> helper class that takes care of startup and makes accessing a <literal>SessionFactory</literal> convenient. - Let's have a look at the implementation: + The following example illustrates the implementation: </para> <programlisting><![CDATA[package util; @@ -601,15 +598,15 @@ }]]></programlisting> <para> - This class does not only produce the global <literal>SessionFactory</literal> in - its static initializer (called once by the JVM when the class is loaded), but also + This class not only produces the global <literal>SessionFactory</literal> in + its static initializer that is called once by the JVM when the class is loaded. It also hides the fact that it uses a static singleton. It might as well lookup the <literal>SessionFactory</literal> from JNDI in an application server. </para> <para> If you give the <literal>SessionFactory</literal> a name in your configuration - file, Hibernate will in fact try to bind it to JNDI after it has been built. + file, Hibernate will try to bind it to JNDI after it has been built. To avoid this code completely you could also use JMX deployment and let the JMX-capable container instantiate and bind a <literal>HibernateService</literal> to JNDI. These advanced options are discussed in the Hibernate reference @@ -617,7 +614,7 @@ </para> <para> - Place <literal>HibernateUtil.java</literal> in the development source directory, in + Place <literal>HibernateUtil.java</literal> in the development source directory in a package next to <literal>events</literal>: </para> @@ -635,17 +632,17 @@ build.xml]]></programlisting> <para> - This should again compile without problems. We finally need to configure a logging - system - Hibernate uses commons logging and leaves you the choice between Log4j and + You now need to configure a logging + system. Hibernate uses commons logging and provides two choices: Log4j and JDK 1.4 logging. Most developers prefer Log4j: copy <literal>log4j.properties</literal> - from the Hibernate distribution (it's in the <literal>etc/</literal> directory) to + from the Hibernate distribution in the <literal>etc/</literal> directory to your <literal>src</literal> directory, next to <literal>hibernate.cfg.xml</literal>. - Have a look at the example configuration and change the settings if you like to have - more verbose output. By default, only Hibernate startup message are shown on stdout. + If you prefer to have + more verbose output than that provided in the example configuration, you can change the settings. By default, only the Hibernate startup message is shown on stdout. </para> <para> - The tutorial infrastructure is complete - and we are ready to do some real work with + The tutorial infrastructure is complete and you are now ready to do some real work with Hibernate. </para> @@ -655,7 +652,7 @@ <title>Loading and storing objects</title> <para> - Finally, we can use Hibernate to load and store objects. We write an + You can use Hibernate to load and store objects. Write an <literal>EventManager</literal> class with a <literal>main()</literal> method: </para> @@ -696,40 +693,40 @@ }]]></programlisting> <para> - We create a new <literal>Event</literal> object, and hand it over to Hibernate. - Hibernate now takes care of the SQL and executes <literal>INSERT</literal>s - on the database. Let's have a look at the <literal>Session</literal> and + You can create a new <literal>Event</literal> object and hand it over to Hibernate. + Hibernate takes care of the SQL and executes <literal>INSERT</literal> + on the database. We will explain the <literal>Session</literal> and <literal>Transaction</literal>-handling code before we run this. </para> <para> - A <literal>Session</literal> is a single unit of work. For now we'll keep things + A <literal>Session</literal> is a single unit of work. For now we will keep things simple and assume a one-to-one granularity between a Hibernate <literal>Session</literal> and a database transaction. To shield our code from the actual underlying transaction - system (in this case plain JDBC, but it could also run with JTA) we use the - <literal>Transaction</literal> API that is available on the Hibernate <literal>Session</literal>. + system we use the + <literal>Transaction</literal> API that is available on the Hibernate <literal>Session</literal>. + In this case plain JDBC, but it could also run with JTA. </para> <para> What does <literal>sessionFactory.getCurrentSession()</literal> do? First, you can call it - as many times and anywhere you like, once you get hold of your <literal>SessionFactory</literal> - (easy thanks to <literal>HibernateUtil</literal>). The <literal>getCurrentSession()</literal> + as many times and anywhere you like, once you get hold of your <literal>SessionFactory</literal>. + This is easy thanks to <literal>HibernateUtil</literal>). The <literal>getCurrentSession()</literal> method always returns the "current" unit of work. Remember that we switched the configuration - option for this mechanism to "thread" in <literal>hibernate.cfg.xml</literal>? Hence, - the current unit of work is bound to the current Java thread that executes our application. - However, this is not the full picture, you also have to consider scope, when a unit of work + option for this mechanism to "thread" in <literal>hibernate.cfg.xml</literal>? The current unit of work is bound to the current Java thread that executes the application. + However, you also have to consider when a unit of work begins and when it ends. </para> <para> - A <literal>Session</literal> begins when it is first needed, when the first call to + A <literal>Session</literal> begins when the first call to <literal>getCurrentSession()</literal> is made. It is then bound by Hibernate to the current thread. When the transaction ends, either through commit or rollback, Hibernate automatically unbinds the <literal>Session</literal> from the thread and closes it for you. If you call <literal>getCurrentSession()</literal> again, you get a new <literal>Session</literal> and can start a new unit of work. This <emphasis>thread-bound</emphasis> programming model is the most - popular way of using Hibernate, as it allows flexible layering of your code (transaction - demarcation code can be separated from data access code, we'll do this later in this tutorial). + popular way of using Hibernate, as it allows flexible layering of your code. Transaction + demarcation code can be separated from data access code. This will be covered later in this tutorial. </para> <para> @@ -738,15 +735,15 @@ for one operation. This is pure coincidence, the example is just not complex enough to show any other approach. The scope of a Hibernate <literal>Session</literal> is flexible but you should never design your application to use a new Hibernate <literal>Session</literal> for - <emphasis>every</emphasis> database operation. So even if you see it a few more times in - the following (very trivial) examples, consider <emphasis>session-per-operation</emphasis> - an anti-pattern. A real (web) application is shown later in this tutorial. + <emphasis>every</emphasis> database operation. Even though it is used in + the following examples, consider <emphasis>session-per-operation</emphasis> + an anti-pattern. A real web application is shown later in the tutorial. </para> <para> - Have a look at <xref linkend="transactions"/> for more information - about transaction handling and demarcation. We also skipped any error handling and - rollback in the previous example. + See <xref linkend="transactions"/> for more information + about transaction handling and demarcation. The previous example also skipped any error handling and + rollback. </para> <para> @@ -768,20 +765,20 @@ <programlisting><![CDATA[C:\hibernateTutorial\>ant run -Daction=store]]></programlisting> <para> - You should see, after compilation, Hibernate starting up and, depending on your - configuration, lots of log output. At the end you will find the following line: + After compilation, you should see Hibernate starting up and, depending on your + configuration, lots of log output. At the end, the following line will be displayed: </para> <programlisting><![CDATA[[java] Hibernate: insert into EVENTS (EVENT_DATE, title, EVENT_ID) values (?, ?, ?)]]></programlisting> <para> - This is the <literal>INSERT</literal> executed by Hibernate, the question marks - represent JDBC bind parameters. To see the values bound as arguments, or to reduce + This is the <literal>INSERT</literal> executed by Hibernate. The question marks + represent JDBC bind parameters. To view the values bound as arguments, or to reduce the verbosity of the log, check your <literal>log4j.properties</literal>. </para> <para> - Now we'd like to list stored events as well, so we add an option to the main method: + To list stored events an option is added to the main method: </para> <programlisting><![CDATA[if (args[0].equals("store")) { @@ -797,7 +794,7 @@ }]]></programlisting> <para> - We also add a new <literal>listEvents() method</literal>: + A new <literal>listEvents() method is also added</literal>: </para> <programlisting><![CDATA[private List listEvents() { @@ -814,46 +811,45 @@ }]]></programlisting> <para> - What we do here is use an HQL (Hibernate Query Language) query to load all existing + Use an HQL (Hibernate Query Language) query to load all existing <literal>Event</literal> objects from the database. Hibernate will generate the appropriate SQL, send it to the database and populate <literal>Event</literal> objects - with the data. You can create more complex queries with HQL, of course. + with the data. You can create more complex queries with HQL. </para> <para> - Now, to execute and test all of this, follow these steps: + To execute and test all of this, follow these steps: </para> <itemizedlist> <listitem> <para> - Run <literal>ant run -Daction=store</literal> to store something into the database + Run <literal>ant run -Daction=store</literal> to store something in the database and, of course, to generate the database schema before through hbm2ddl. </para> </listitem> <listitem> <para> - Now disable hbm2ddl by commenting out the property in your <literal>hibernate.cfg.xml</literal> - file. Usually you only leave it turned on in continuous unit testing, but another - run of hbm2ddl would <emphasis>drop</emphasis> everything you have stored - the - <literal>create</literal> configuration setting actually translates into "drop all - tables from the schema, then re-create all tables, when the SessionFactory is build". + Disable hbm2ddl by commenting out the property in your <literal>hibernate.cfg.xml</literal> + file. It is only turned on in continuous unit testing. Another + run of hbm2ddl would <emphasis>drop</emphasis> everything you have stored. The + <literal>create</literal> configuration setting translates into "drop all + tables from the schema, then re-create all tables, when the SessionFactory is built". </para> </listitem> </itemizedlist> <para> - If you now call Ant with <literal>-Daction=list</literal>, you should see the events - you have stored so far. You can of course also call the <literal>store</literal> action a few - times more. + If you can call Ant with <literal>-Daction=list</literal>, you will be able to view the events + you have stored so far. You can also call the <literal>store</literal> action. </para> <para> - Note: Most new Hibernate users fail at this point and we see questions about - <emphasis>Table not found</emphasis> error messages regularly. However, if you follow the + Most new Hibernate users fail at this point and we regularly receive questions relating to + <emphasis>Table not found</emphasis> error messages. However, if you follow the steps outlined above you will not have this problem, as hbm2ddl creates the database schema on the first run, and subsequent application restarts will use this schema. If - you change the mapping and/or database schema, you have to re-enable hbm2ddl once again. + you change the mapping and/or database schema, you will have to re-enable hbm2ddl. </para> </sect2> @@ -864,15 +860,15 @@ <title>Part 2 - Mapping associations</title> <para> - We mapped a persistent entity class to a table. Let's build on this and add some class associations. - First we'll add people to our application, and store a list of events they participate in. + You have mapped a persistent entity class to a table. You can now build on this by adding some class associations. + First you will add people to your application, and store a list of events they participate in. </para> <sect2 id="tutorial-associations-mappinguser" revision="1"> <title>Mapping the Person class</title> <para> - The first cut of the <literal>Person</literal> class is simple: + The first cut of the <literal>Person</literal> class looks like this: </para> <programlisting><![CDATA[package events; @@ -891,8 +887,8 @@ }]]></programlisting> <para> - Create a new mapping file called <literal>Person.hbm.xml</literal> (don't forget the - DTD reference at the top): + Create a new mapping file called <literal>Person.hbm.xml</literal>. Do not forget the + DTD reference at the top: </para> <programlisting><![CDATA[<hibernate-mapping> @@ -916,9 +912,9 @@ <mapping resource="events/Person.hbm.xml"/>]]></programlisting> <para> - We'll now create an association between these two entities. Obviously, persons + Create an association between these two entities. Persons can participate in events, and events have participants. The design questions - we have to deal with are: directionality, multiplicity, and collection + you have to deal with are: directionality, multiplicity, and collection behavior. </para> @@ -928,15 +924,15 @@ <title>A unidirectional Set-based association</title> <para> - We'll add a collection of events to the <literal>Person</literal> class. That way we can + By adding a collection of events to the <literal>Person</literal> class, you can easily navigate to the events for a particular person, without executing an explicit query - - by calling <literal>aPerson.getEvents()</literal>. We use a Java collection, a <literal>Set</literal>, - because the collection will not contain duplicate elements and the ordering is not relevant for us. + by calling <literal>aPerson.getEvents()</literal>. A Java collection, a <literal>Set</literal>, is used + because the collection will not contain duplicate elements and the ordering is not relevant to our examples. </para> <para> - We need a unidirectional, many-valued associations, implemented with a <literal>Set</literal>. - Let's write the code for this in the Java classes and then map it: + We need unidirectional, many-valued associations, implemented with a <literal>Set</literal>. + Write the code for this in the Java classes and then map it: </para> <programlisting><![CDATA[public class Person { @@ -953,13 +949,13 @@ }]]></programlisting> <para> - Before we map this association, think about the other side. Clearly, we could just keep this - unidirectional. Or, we could create another collection on the <literal>Event</literal>, if we - want to be able to navigate it bi-directional, i.e. <literal>anEvent.getParticipants()</literal>. - This is not necessary, from a functional perspective. You could always execute an explicit query + Before you map this association, consider the other side. You could just keep this + unidirectional. Or, you could create another collection on the <literal>Event</literal>, if you + want to be able to navigate it bi-directional, i.e., <literal>anEvent.getParticipants()</literal>. + This is not necessary, from a functional perspective. You can always execute an explicit query to retrieve the participants for a particular event. This is a design choice left to you, but what - is clear from this discussion is the multiplicity of the association: "many" valued on both sides, - we call this a <emphasis>many-to-many</emphasis> association. Hence, we use Hibernate's + is clear from this discussion is the multiplicity of the association: "many" valued on both sides + is called a <emphasis>many-to-many</emphasis> association. Hence, we use Hibernate's many-to-many mapping: </para> @@ -979,14 +975,14 @@ </class>]]></programlisting> <para> - Hibernate supports all kinds of collection mappings, a <literal>&lt;set&gt;</literal> being most - common. For a many-to-many association (or <emphasis>n:m</emphasis> entity relationship), an - association table is needed. Each row in this table represents a link between a person and an event. + Hibernate supports a broad range of collection mappings, a <literal>&lt;set&gt;</literal> being most + common. For a many-to-many association, or <emphasis>n:m</emphasis> entity relationship, an + association table is required. Each row in this table represents a link between a person and an event. The table name is configured with the <literal>table</literal> attribute of the <literal>set</literal> - element. The identifier column name in the association, for the person's side, is defined with the + element. The identifier column name in the association, for the person side, is defined with the <literal>&lt;key&gt;</literal> element, the column name for the event's side with the <literal>column</literal> attribute of the <literal>&lt;many-to-many&gt;</literal>. You also - have to tell Hibernate the class of the objects in your collection (correct: the class on the + have to tell Hibernate the class of the objects in your collection (the class on the other side of the collection of references). </para> @@ -1014,7 +1010,7 @@ <title>Working the association</title> <para> - Let's bring some people and events together in a new method in <literal>EventManager</literal>: + Now we will bring some people and events together in a new method in <literal>EventManager</literal>: </para> <programlisting><![CDATA[private void addPersonToEvent(Long personId, Long eventId) { @@ -1032,23 +1028,23 @@ <para> After loading a <literal>Person</literal> and an <literal>Event</literal>, simply - modify the collection using the normal collection methods. As you can see, there is no explicit call - to <literal>update()</literal> or <literal>save()</literal>, Hibernate automatically + modify the collection using the normal collection methods. There is no explicit call + to <literal>update()</literal> or <literal>save()</literal>; Hibernate automatically detects that the collection has been modified and needs to be updated. This is called <emphasis>automatic - dirty checking</emphasis>, and you can also try it by modifying the name or the date property of + dirty checking</emphasis>. You can also try it by modifying the name or the date property of any of your objects. As long as they are in <emphasis>persistent</emphasis> state, that is, bound to a particular Hibernate <literal>Session</literal> (i.e. they have been just loaded or saved in a unit of work), Hibernate monitors any changes and executes SQL in a write-behind fashion. The process of synchronizing the memory state with the database, usually only at the end of a unit of - work, is called <emphasis>flushing</emphasis>. In our code, the unit of work ends with a commit - (or rollback) of the database transaction - as defined by the <literal>thread</literal> configuration + work, is called <emphasis>flushing</emphasis>. In our code, the unit of work ends with a commit, + or rollback, of the database transaction. This is defined by the <literal>thread</literal> configuration option for the <literal>CurrentSessionContext</literal> class. </para> <para> - You might of course load person and event in different units of work. Or you modify an object + You can load person and event in different units of work. Or you can modify an object outside of a <literal>Session</literal>, when it is not in persistent state (if it was persistent - before, we call this state <emphasis>detached</emphasis>). You can even modify a collection when + before, this state is called <emphasis>detached</emphasis>). You can even modify a collection when it is detached: </para> @@ -1081,16 +1077,15 @@ }]]></programlisting> <para> - The call to <literal>update</literal> makes a detached object persistent again, you could - say it binds it to a new unit of work, so any modifications you made to it while detached + The call to <literal>update</literal> makes a detached object persistent again by binding it to a new unit of work, so any modifications you made to it while detached can be saved to the database. This includes any modifications (additions/deletions) you made to a collection of that entity object. </para> <para> - Well, this is not much use in our current situation, but it's an important concept you can - design into your own application. For now, complete this exercise by adding a new action - to the <literal>EventManager</literal>'s main method and call it from the command line. If + This is not much use in our example, but it is an important concept you can + incorporate into your own application. Complete this exercise by adding a new action + to the main method of the <literal>EventManager</literal> and call it from the command line. If you need the identifiers of a person and an event - the <literal>save()</literal> method returns it (you might have to modify some of the previous methods to return that identifier): </para> @@ -1103,20 +1098,20 @@ }]]></programlisting> <para> - This was an example of an association between two equally important classes, two entities. + This is an example of an association between two equally important classes, two entities. As mentioned earlier, there are other classes and types in a typical model, usually "less important". Some you have already seen, like an <literal>int</literal> or a <literal>String</literal>. We call these classes <emphasis>value types</emphasis>, and their instances <emphasis>depend</emphasis> - on a particular entity. Instances of these types don't have their own identity, nor are they - shared between entities (two persons don't reference the same <literal>firstname</literal> - object, even if they have the same first name). Of course, value types can not only be found in - the JDK (in fact, in a Hibernate application all JDK classes are considered value types), but - you can also write dependent classes yourself, <literal>Address</literal> or <literal>MonetaryAmount</literal>, - for example. + on a particular entity. Instances of these types do not have their own identity, nor are they + shared between entities. Two persons do not reference the same <literal>firstname</literal> + object, even if they have the same first name. Value types cannot only be found in + the JDK , but + you can also write dependent classes yourself (<literal>Address</literal> or <literal>MonetaryAmount</literal>, + for example). In fact, in a Hibernate application all JDK classes are considered value types. </para> <para> - You can also design a collection of value types. This is conceptually very different from a + You can also design a collection of value types. This is conceptually different from a collection of references to other entities, but looks almost the same in Java. </para> @@ -1126,8 +1121,8 @@ <title>Collection of values</title> <para> - We add a collection of value typed objects to the <literal>Person</literal> entity. We want to - store email addresses, so the type we use is <literal>String</literal>, and the collection is + You can add a collection of value typed objects to the <literal>Person</literal> entity. If you want to + store email addresses, the type you use is <literal>String</literal>, and the collection is again a <literal>Set</literal>: </para> <programlisting><![CDATA[private Set emailAddresses = new HashSet(); @@ -1141,7 +1136,7 @@ }]]></programlisting> <para> - The mapping of this <literal>Set</literal>: + The mapping of this <literal>Set</literal> is as follows: </para> <programlisting><![CDATA[<set name="emailAddresses" table="PERSON_EMAIL_ADDR"> @@ -1150,17 +1145,17 @@ </set>]]></programlisting> <para> - The difference compared with the earlier mapping is the <literal>element</literal> part, which tells Hibernate that the collection + The difference compared with the earlier mapping is the <literal>element</literal> part which tells Hibernate that the collection does not contain references to another entity, but a collection of elements of type - <literal>String</literal> (the lowercase name tells you it's a Hibernate mapping type/converter). - Once again, the <literal>table</literal> attribute of the <literal>set</literal> element determines + <literal>String</literal>. The lowercase name tells you it is a Hibernate mapping type/converter. + Again the <literal>table</literal> attribute of the <literal>set</literal> element determines the table name for the collection. The <literal>key</literal> element defines the foreign-key column name in the collection table. The <literal>column</literal> attribute in the <literal>element</literal> element defines the column name where the <literal>String</literal> values will actually be stored. </para> <para> - Have a look at the updated schema: + Here is the updated schema: </para> <programlisting><![CDATA[ @@ -1178,14 +1173,14 @@ ]]></programlisting> <para> - You can see that the primary key of the collection table is in fact a composite key, - using both columns. This also implies that there can't be duplicate email addresses + You can see that the primary key of the collection table is in fact a composite key that + uses both columns. This also implies that there cannot be duplicate email addresses per person, which is exactly the semantics we need for a set in Java. </para> <para> - You can now try and add elements to this collection, just like we did before by - linking persons and events. It's the same code in Java: + You can now try to add elements to this collection, just like we did before by + linking persons and events. It is the same code in Java: </para> <programlisting><![CDATA[private void addEmailToPerson(Long personId, String emailAddress) { @@ -1202,7 +1197,7 @@ }]]></programlisting> <para> - This time we didn't use a <emphasis>fetch</emphasis> query to initialize the collection. + This time we did not use a <emphasis>fetch</emphasis> query to initialize the collection. Hence, the call to its getter method will trigger an additional select to initialize it, so we can add an element to it. Monitor the SQL log and try to optimize this with an eager fetch. @@ -1214,11 +1209,11 @@ <title>Bi-directional associations</title> <para> - Next we are going to map a bi-directional association - making the association between - person and event work from both sides in Java. Of course, the database schema doesn't - change, we still have many-to-many multiplicity. A relational database is more flexible - than a network programming language, so it doesn't need anything like a navigation - direction - data can be viewed and retrieved in any possible way. + Next you will map a bi-directional association. You will make the association between + person and event work from both sides in Java. The database schema does not + change, so you will still have many-to-many multiplicity. A relational database is more flexible + than a network programming language, so it does not need a navigation + direction; data can be viewed and retrieved in any possible way. </para> <para> @@ -1236,7 +1231,7 @@ }]]></programlisting> <para> - Now map this side of the association too, in <literal>Event.hbm.xml</literal>. + Now map this side of the association in <literal>Event.hbm.xml</literal>. </para> <programlisting><![CDATA[<set name="participants" table="PERSON_EVENT" inverse="true"> @@ -1245,17 +1240,17 @@ </set>]]></programlisting> <para> - As you see, these are normal <literal>set</literal> mappings in both mapping documents. - Notice that the column names in <literal>key</literal> and <literal>many-to-many</literal> are - swapped in both mapping documents. The most important addition here is the + These are normal <literal>set</literal> mappings in both mapping documents. + Notice that the column names in <literal>key</literal> and <literal>many-to-many</literal> + swap in both mapping documents. The most important addition here is the <literal>inverse="true"</literal> attribute in the <literal>set</literal> element of the <literal>Event</literal>'s collection mapping. </para> <para> - What this means is that Hibernate should take the other side - the <literal>Person</literal> class - + What this means is that Hibernate should take the other side, the <literal>Person</literal> class, when it needs to find out information about the link between the two. This will be a lot easier to - understand once you see how the bi-directional link between our two entities is created . + understand once you see how the bi-directional link between our two entities is created. </para> </sect2> @@ -1266,16 +1261,16 @@ <para> First, keep in mind that Hibernate does not affect normal Java semantics. How did we create a link between a <literal>Person</literal> and an <literal>Event</literal> in the unidirectional - example? We added an instance of <literal>Event</literal> to the collection of event references, - of an instance of <literal>Person</literal>. So, obviously, if we want to make this link working - bi-directional, we have to do the same on the other side - adding a <literal>Person</literal> - reference to the collection in an <literal>Event</literal>. This "setting the link on both sides" - is absolutely necessary and you should never forget doing it. + example? You add an instance of <literal>Event</literal> to the collection of event references, + of an instance of <literal>Person</literal>. If you want to make this link + bi-directional, you have to do the same on the other side by adding a <literal>Person</literal> + reference to the collection in an <literal>Event</literal>. This process of "setting the link on both sides" + is absolutely necessary with bi-directional links. </para> <para> Many developers program defensively and create link management methods to - correctly set both sides, e.g. in <literal>Person</literal>: + correctly set both sides (for example, in <literal>Person</literal>): </para> <programlisting><![CDATA[protected Set getEvents() { @@ -1297,25 +1292,24 @@ }]]></programlisting> <para> - Notice that the get and set methods for the collection are now protected - this allows classes in the - same package and subclasses to still access the methods, but prevents everybody else from messing - with the collections directly (well, almost). You should probably do the same with the collection + The get and set methods for the collection are now protected. This allows classes in the + same package and subclasses to still access the methods, but prevents everybody else from altering + the collections directly. Repeat the steps for the collection on the other side. </para> <para> What about the <literal>inverse</literal> mapping attribute? For you, and for Java, a bi-directional - link is simply a matter of setting the references on both sides correctly. Hibernate however doesn't + link is simply a matter of setting the references on both sides correctly. Hibernate, however, does not have enough information to correctly arrange SQL <literal>INSERT</literal> and <literal>UPDATE</literal> - statements (to avoid constraint violations), and needs some help to handle bi-directional associations - properly. Making one side of the association <literal>inverse</literal> tells Hibernate to basically - ignore it, to consider it a <emphasis>mirror</emphasis> of the other side. That's all that is necessary - for Hibernate to work out all of the issues when transformation a directional navigation model to - a SQL database schema. The rules you have to remember are straightforward: All bi-directional associations + statements (to avoid constraint violations). Making one side of the association <literal>inverse</literal> tells Hibernate to consider it a <emphasis>mirror</emphasis> of the other side. That is all that is necessary + for Hibernate to resolve any issues that arise when transforming a directional navigation model to + a SQL database schema. The rules are straightforward: all bi-directional associations need one side as <literal>inverse</literal>. In a one-to-many association it has to be the many-side, - in many-to-many association you can pick either side, there is no difference. + and in many-to-many association you can select either side. </para> + <para>In the next section we will turn this into a small web application.</para> </sect2> </sect1> @@ -1324,12 +1318,8 @@ <title>Part 3 - The EventManager web application</title> <para> - Let's turn the following discussion into a small web application... - </para> - - <para> A Hibernate web application uses <literal>Session</literal> and <literal>Transaction</literal> - almost like a standalone application. However, some common patterns are useful. We now write + almost like a standalone application. However, some common patterns are useful. You can now write an <literal>EventManagerServlet</literal>. This servlet can list all events stored in the database, and it provides an HTML form to enter new events. </para> @@ -1338,7 +1328,7 @@ <title>Writing the basic servlet</title> <para> - Create a new class in your source directory, in the <literal>events</literal> + Create a new class in your source directory in the <literal>events</literal> package: </para> @@ -1352,7 +1342,7 @@ }]]></programlisting> <para> - The servlet handles HTTP <literal>GET</literal> requests only, hence, the method + The servlet handles HTTP <literal>GET</literal> requests only. It is for this reason that the method we implement is <literal>doGet()</literal>: </para> @@ -1382,12 +1372,12 @@ }]]></programlisting> <para> - The pattern we are applying here is called <emphasis>session-per-request</emphasis>. + The pattern applied here is called <emphasis>session-per-request</emphasis>. When a request hits the servlet, a new Hibernate <literal>Session</literal> is opened through the first call to <literal>getCurrentSession()</literal> on the - <literal>SessionFactory</literal>. Then a database transaction is started&mdash;all - data access as to occur inside a transaction, no matter if data is read or written - (we don't use the auto-commit mode in applications). + <literal>SessionFactory</literal>. A database transaction is then started. All + data access occurs inside a transaction irrespective of whether the data is read or written. + Do not use the auto-commit mode in applications. </para> <para> @@ -1399,17 +1389,17 @@ <para> Next, the possible actions of the request are processed and the response HTML - is rendered. We'll get to that part soon. + is rendered. We will get to that part soon. </para> <para> - Finally, the unit of work ends when processing and rendering is complete. If any - problem occurred during processing or rendering, an exception will be thrown + Finally, the unit of work ends when processing and rendering are complete. If any + problems occurred during processing or rendering, an exception will be thrown and the database transaction rolled back. This completes the <literal>session-per-request</literal> pattern. Instead of the transaction - demarcation code in every servlet you could also write a servlet filter. - See the Hibernate website and Wiki for more information about this pattern, - called <emphasis>Open Session in View</emphasis>&mdash;you'll need it as soon + demarcation code in every servlet, you could also write a servlet filter. + See the Hibernate website and Wiki for more information about this pattern + called <emphasis>Open Session in View</emphasis>. You will need it as soon as you consider rendering your view in JSP, not in a servlet. </para> @@ -1419,7 +1409,7 @@ <title>Processing and rendering</title> <para> - Let's implement the processing of the request and rendering of the page. + Now you can implement the processing of the request and the rendering of the page. </para> <programlisting><![CDATA[// Write HTML header @@ -1450,7 +1440,7 @@ out.close();]]></programlisting> <para> - Granted, this coding style with a mix of Java and HTML would not scale + This coding style, with a mix of Java and HTML, would not scale in a more complex application&mdash;keep in mind that we are only illustrating basic Hibernate concepts in this tutorial. The code prints an HTML header and a footer. Inside this page, an HTML form for event entry and @@ -1511,12 +1501,12 @@ }]]></programlisting> <para> - That's it, the servlet is complete. A request to the servlet will be processed + The servlet is now complete. A request to the servlet will be processed in a single <literal>Session</literal> and <literal>Transaction</literal>. As earlier in the standalone application, Hibernate can automatically bind these objects to the current thread of execution. This gives you the freedom to layer your code and access the <literal>SessionFactory</literal> in any way you like. - Usually you'd use a more sophisticated design and move the data access code + Usually you would use a more sophisticated design and move the data access code into data access objects (the DAO pattern). See the Hibernate Wiki for more examples. </para> @@ -1527,7 +1517,7 @@ <title>Deploying and testing</title> <para> - To deploy this application you have to create a web archive, a WAR. Add the + To deploy this application you have to create a web archive, or what is known as a WAR. Add the following Ant target to your <literal>build.xml</literal>: </para> @@ -1565,9 +1555,9 @@ </web-app>]]></programlisting> <para> - Before you compile and deploy the web application, note that an additional library - is required: <literal>jsdk.jar</literal>. This is the Java servlet development kit, - if you don't have this library already, get it from the Sun website and copy it to + Before you compile and deploy the web application, an additional library + is required: <literal>jsdk.jar</literal>. This is the Java servlet development kit. + If you do not have this library already, get it from the Sun website and copy it to your library directory. However, it will be only used for compilation and excluded from the WAR package. </para> @@ -1575,8 +1565,8 @@ <para> To build and deploy call <literal>ant war</literal> in your project directory and copy the <literal>hibernate-tutorial.war</literal> file into your Tomcat - <literal>webapp</literal> directory. If you don't have Tomcat installed, download - it and follow the installation instructions. You don't have to change any Tomcat + <literal>webapp</literal> directory. If you do not have Tomcat installed, download + it and follow the installation instructions. You do not have to change any Tomcat configuration to deploy this application though. </para> @@ -1602,14 +1592,14 @@ <para> If you already feel confident with Hibernate, continue browsing through the reference - documentation table of contents for topics you find interesting - most asked are + documentation table of contents for topics you find interesting. The most popular are transactional processing (<xref linkend="transactions"/>), fetch performance (<xref linkend="performance"/>), or the usage of the API (<xref linkend="objectstate"/>) and the query features (<xref linkend="objectstate-querying"/>). </para> <para> - Don't forget to check the Hibernate website for more (specialized) tutorials. + More tutorials are available from the Hibernate website. </para> </sect1> Modified: core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/xml.xml =================================================================== --- core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/xml.xml 2009-01-29 05:20:27 UTC (rev 15829) +++ core/branches/Branch_3_3/documentation/manual/src/main/docbook/en-US/content/xml.xml 2009-01-29 19:56:06 UTC (rev 15830) @@ -29,17 +29,17 @@ <title>XML Mapping</title> <para><emphasis> - Note that this is an experimental feature in Hibernate 3.0 and is under - extremely active development. + XML Mapping is an experimental feature in Hibernate 3.0 and is currently under + active development. </emphasis></para> <sect1 id="xml-intro" revision="1"> <title>Working with XML data</title> <para> - Hibernate lets you work with persistent XML data in much the same way + Hibernate allows you to work with persistent XML data in much the same way you work with persistent POJOs. A parsed XML tree can be thought of - as just another way to represent the relational data at the object level, + as another way of representing the relational data at the object level, instead of POJOs. </para> @@ -59,9 +59,9 @@ </para> <para> - A single mapping may be used to simultaneously map properties of a class + A single mapping can be used to simultaneously map properties of a class and nodes of an XML document to the database, or, if there is no class to map, - it may be used to map just the XML. + it can be used to map just the XML. </para> <sect2 id="xml-intro-mapping"> @@ -126,8 +126,8 @@ <para> This mapping allows you to access the data as a dom4j tree, or as a graph of - property name/value pairs (java <literal>Map</literal>s). The property names - are purely logical constructs that may be referred to in HQL queries. + property name/value pairs or java <literal>Map</literal>s. The property names + are purely logical constructs that can be referred to in HQL queries. </para> </sect2> @@ -138,25 +138,25 @@ <title>XML mapping metadata</title> <para> - Many Hibernate mapping elements accept the <literal>node</literal> attribute. - This let's you specify the name of an XML attribute or element that holds the + A range of Hibernate mapping elements accept the <literal>node</literal> attribute. + This lets you specify the name of an XML attribute or element that holds the property or entity data. The format of the <literal>node</literal> attribute must be one of the following: </para> <itemizedlist spacing="compact"> <listitem> - <para><literal>"element-name"</literal> - map to the named XML element</para> + <para><literal>"element-name"</literal>: map to the named XML element</para> </listitem> <listitem> - <para><literal>"@attribute-name"</literal> - map to the named XML attribute</para> + <para><literal>"@attribute-name"</literal>: map to the named XML attribute</para> </listitem> <listitem> - <para><literal>"."</literal> - map to the parent element</para> + <para><literal>"."</literal>: map to the parent element</para> </listitem> <listitem> <para> - <literal>"element-name/@attribute-name"</literal> - + <literal>"element-name/@attribute-name"</literal>: map to the named attribute of the named element </para> </listitem> @@ -169,12 +169,12 @@ will be embedded directly in the XML tree for the entity that owns the association. Otherwise, if <literal>embed-xml="false"</literal>, then only the referenced identifier value will appear in the XML for single point associations and - collections will simply not appear at all. + collections will not appear at all. </para> <para> - You should be careful not to leave <literal>embed-xml="true"</literal> for - too many associations, since XML does not deal well with circularity! + Do not leave <literal>embed-xml="true"</literal> for + too many associations, since XML does not deal well with circularity. </para> <programlisting><![CDATA[<class name="Customer" @@ -213,14 +213,14 @@ </class>]]></programlisting> <para> - in this case, we have decided to embed the collection of account ids, but not + In this case, the collection of account ids is embedded, but not the actual account data. The following HQL query: </para> <programlisting><![CDATA[from Customer c left join fetch c.accounts where c.lastName like :lastName]]></programlisting> <para> - Would return datasets such as this: + would return datasets such as this: </para> <programlisting><![CDATA[<customer id="123456789"> @@ -263,7 +263,7 @@ <title>Manipulating XML data</title> <para> - Let's rearead and update XML documents in the application. We do this by + You can also re-read and update XML documents in the application. You can do this by obtaining a dom4j session: </para> @@ -303,8 +303,8 @@ session.close();]]></programlisting> <para> - It is extremely useful to combine this feature with Hibernate's <literal>replicate()</literal> - operation to implement XML-based data import/export. + When implementing XML-based data import/export, it is useful to combine this feature with Hibernate's <literal>replicate()</literal> + operation. </para> </sect1>