2:27 a.m.
Author: epbernard
Date: 2010-02-26 03:27:46 -0500 (Fri, 26 Feb 2010)
New Revision: 18899
Modified:
core/trunk/annotations/src/main/docbook/en/modules/entity.xml
Log:
HHH-4933 minor fixes while reading
Modified: core/trunk/annotations/src/main/docbook/en/modules/entity.xml
===================================================================
--- core/trunk/annotations/src/main/docbook/en/modules/entity.xml 2010-02-25 20:32:24 UTC
(rev 18898)
+++ core/trunk/annotations/src/main/docbook/en/modules/entity.xml 2010-02-26 08:27:46 UTC
(rev 18899)
@@ -837,7 +837,11 @@
@Id @GeneratedValue Integer id;
}</programlisting>
- <para>But an identifier does not have to be a single property, it ca
+ <para>If you are interested in more examples of "derived
identities",
+ the JPA 2 specification has a great set of them in chapter
+ 2.4.1.3.</para>
+
+ <para>But an identifier does not have to be a single property, it can
be composed of several properties.</para>
</section>
@@ -1204,19 +1208,17 @@
<title>Table per class</title>
<para>This strategy has many drawbacks (esp. with polymorphic queries
- and associations) explained in the EJB3 spec, the Hibernate reference
+ and associations) explained in the JPA spec, the Hibernate reference
documentation, Hibernate in Action, and many other places. Hibernate
work around most of them implementing this strategy using <literal>SQL
UNION</literal> queries. It is commonly used for the top level of an
inheritance hierarchy:</para>
- <programlisting>
-@Entity
+ <programlisting>@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
-public class Flight implements Serializable {
- </programlisting>
+public class Flight implements Serializable { ... } </programlisting>
- <para>This strategy support one to many associations provided that
+ <para>This strategy supports one-to-many associations provided that
they are bidirectional. This strategy does not support the
<literal>IDENTITY</literal> generator strategy: the id has to be
shared across several tables. Consequently, when using this strategy,
@@ -1231,8 +1233,7 @@
same table, instances are distinguished by a special discriminator
column:</para>
- <programlisting>
-@Entity
+ <programlisting>@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(
name="planetype",
@@ -1243,8 +1244,7 @@
@Entity
@DiscriminatorValue("A320")
-public class A320 extends Plane { ... }
- </programlisting>
+public class A320 extends Plane { ... } </programlisting>
<para><classname>Plane</classname> is the superclass, it
defines the
inheritance strategy
<literal>InheritanceType.SINGLE_TABLE</literal>.
@@ -1273,8 +1273,7 @@
<literal>@PrimaryKeyJoinColumns</literal> annotations define the
primary key(s) of the joined subclass table:</para>
- <programlisting>
-@Entity
+ <programlisting>@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public class Boat implements Serializable { ... }
@@ -1283,8 +1282,7 @@
@Entity
@PrimaryKeyJoinColumn(name="BOAT_ID")
-public class AmericaCupClass extends Boat { ... }
- </programlisting>
+public class AmericaCupClass extends Boat { ... } </programlisting>
<para>All of the above entities use the
<literal>JOINED</literal>
strategy, the <literal>Ferry</literal> table is joined with the
@@ -1378,7 +1376,10 @@
@Entity
@AttributeOverride( name="altitude", column =
@Column(name="fld_altitude") )
-@AssociationOverride( name="propulsion", joinColumns =
@JoinColumn(name="fld_propulsion_fk") )
+@AssociationOverride(
+ name="propulsion",
+ joinColumns = @JoinColumn(name="fld_propulsion_fk")
+)
public class Plane extends FlyingObject {
...
}</programlisting>
@@ -1410,13 +1411,12 @@
(note that this FK column in the database should be constrained unique
to simulate one-to-one multiplicity), or a association table is used
to store the link between the 2 entities (a unique constraint has to
- be defined on each fk to ensure the one to one multiplicity)</para>
+ be defined on each fk to ensure the one to one multiplicity).</para>
<para>First, we map a real one-to-one association using shared primary
keys:</para>
- <programlisting>
-@Entity
+ <programlisting>@Entity
public class Body {
@Id
public Long getId() { return id; }
@@ -1427,25 +1427,22 @@
return heart;
}
...
-}
- </programlisting>
+} </programlisting>
- <programlisting>
-@Entity
+ <programlisting>@Entity
public class Heart {
@Id
public Long getId() { ...}
-}
- </programlisting>
+} </programlisting>
- <para>The one to one is marked as true by using the
- <literal>@PrimaryKeyJoinColumn</literal> annotation.</para>
+ <para>The <literal>@PrimaryKeyJoinColumn</literal> annotation
does say
+ that the primary key of the entity is used as the foreign key value to
+ the associated entity.</para>
<para>In the following example, the associated entities are linked
- through a foreign key column:</para>
+ through an explicit foreign key column:</para>
- <programlisting>
-@Entity
+ <programlisting>@Entity
public class Customer implements Serializable {
@OneToOne(cascade = CascadeType.ALL)
<emphasis
role="bold">@JoinColumn(name="passport_fk")</emphasis>
@@ -1458,8 +1455,7 @@
@OneToOne(<emphasis role="bold">mappedBy =
"passport"</emphasis>)
public Customer getOwner() {
...
-}
- </programlisting>
+} </programlisting>
<para>A <classname>Customer</classname> is linked to a
<classname>Passport</classname>, with a foreign key column named