[hibernate-commits] Hibernate SVN: r15281 - core/trunk/core/src/main/java/org/hibernate/criterion.

[hibernate-commits at lists.jboss.org]

Author: steve.ebersole at jboss.com
Date: 2008-10-08 07:44:03 -0400 (Wed, 08 Oct 2008)
New Revision: 15281

Modified:
   core/trunk/core/src/main/java/org/hibernate/criterion/Projection.java
Log:
javadoc

Modified: core/trunk/core/src/main/java/org/hibernate/criterion/Projection.java
===================================================================
--- core/trunk/core/src/main/java/org/hibernate/criterion/Projection.java	2008-10-08 11:43:20 UTC (rev 15280)
+++ core/trunk/core/src/main/java/org/hibernate/criterion/Projection.java	2008-10-08 11:44:03 UTC (rev 15281)
@@ -32,73 +32,106 @@
 import org.hibernate.type.Type;
 
 /**
- * An object-oriented representation of a query result set projection 
- * in a <tt>Criteria</tt> query. Built-in projection types are provided 
- * by the <tt>Projections</tt> factory class.
- * This interface might be implemented by application classes that
- * define custom projections.
+ * An object-oriented representation of a query result set projection  in a {@link Criteria} query.
+ * Built-in projection types are provided  by the {@link Projections} factory class.  This interface might be
+ * implemented by application classes that define custom projections.
  *
+ * @author Gavin King
+ * @author Steve Ebersole
  * @see Projections
- * @see org.hibernate.Criteria
- * @author Gavin King
+ * @see Criteria
  */
 public interface Projection extends Serializable {
 
 	/**
-	 * Render the SQL fragment
-	 * @param criteriaQuery
-	 * @param columnAlias
-	 * @return String
-	 * @throws HibernateException
+	 * Render the SQL fragment to be used in the <tt>SELECT</tt> clause.
+	 *
+	 * @param criteria The local criteria to which this project is attached (for resolution).
+	 * @param position The number of columns rendered in the <tt>SELECT</tt> clause before this projection.  Generally
+	 * speaking this is useful to ensure uniqueness of the individual columns aliases.
+	 * @param criteriaQuery The overall criteria query instance.
+	 * @return The SQL fragment to plug into the <tt>SELECT</tt>
+	 * @throws HibernateException Indicates a problem performing the rendering
 	 */
-	public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery) 
-	throws HibernateException;
-	
+	public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery)
+			throws HibernateException;
+
 	/**
-	 * Render the SQL fragment to be used in the group by clause
-	 * @param criteriaQuery
-	 * @param columnAlias
-	 * @return String
-	 * @throws HibernateException
+	 * Render the SQL fragment to be used in the <tt>GROUP BY</tt> clause
+	 *
+	 * @param criteria The local criteria to which this project is attached (for resolution).
+	 * @param criteriaQuery The overall criteria query instance.
+	 * @return The SQL fragment to plug into the <tt>GROUP BY</tt>
+	 * @throws HibernateException Indicates a problem performing the rendering
 	 */
-	public String toGroupSqlString(Criteria criteria, CriteriaQuery criteriaQuery) 
-	throws HibernateException;
-	
+	public String toGroupSqlString(Criteria criteria, CriteriaQuery criteriaQuery)
+			throws HibernateException;
+
 	/**
-	 * Return types returned by the rendered SQL fragment
-	 * @param criteria
-	 * @param criteriaQuery 
-	 * @return Type[]
-	 * @throws HibernateException
+	 * Types returned by the rendered SQL {@link #toSqlString fragment}.  In other words what are the types
+	 * that would represent the values this projection asked to be pulled into the result set?
+	 *
+	 * @param criteria The local criteria to which this project is attached (for resolution).
+	 * @param criteriaQuery The overall criteria query instance.
+	 * @return The return types.
+	 * @throws HibernateException Indicates a problem resolving the types
 	 */
-	public Type[] getTypes(Criteria criteria, CriteriaQuery criteriaQuery) 
-	throws HibernateException;
+	public Type[] getTypes(Criteria criteria, CriteriaQuery criteriaQuery)
+			throws HibernateException;
+
 	/**
-	 * Return types for a particular user-visible alias
+	 * Get the return types for a particular user-visible alias.
+	 * <p/>
+	 * Differs from {@link #getTypes(org.hibernate.Criteria, CriteriaQuery)} in that here we are only interested in
+	 * the types related to the given criteria-level alias.
+	 *
+	 * @param alias The criteria-level alias for which to find types.
+	 * @param criteria The local criteria to which this project is attached (for resolution).
+	 * @param criteriaQuery The overall criteria query instance.
+	 * @return The return types; expected to return null if this projection does not understand this alias.
+	 * @throws HibernateException Indicates a problem resolving the types
 	 */
-	public Type[] getTypes(String alias, Criteria criteria, CriteriaQuery criteriaQuery) 
-	throws HibernateException;
-		
+	public Type[] getTypes(String alias, Criteria criteria, CriteriaQuery criteriaQuery)
+			throws HibernateException;
+
+
 	/**
-	 * Get the SQL select clause column aliases
+	 * Get the SQL column aliases used by this projection for the columns it writes for inclusion into the
+	 * <tt>SELECT</tt> clause ({@link #toSqlString}.  Hibernate always uses column aliases to extract data from the
+	 * JDBC {@link java.sql.ResultSet}, so it is important that these be implemented correctly in order for
+	 * Hibernate to be able to extract these val;ues correctly.
+	 *
+	 * @param position Just as in {@link #toSqlString}, represents the number of <b>columns</b> rendered
+	 * prior to this projection.
+	 * @return The columns aliases.
 	 */
-	public String[] getColumnAliases(int loc);
+	public String[] getColumnAliases(int position);
+
 	/**
-	 * Get the SQL select clause column aliases for a particular
-	 * user-visible alias
+	 * Get the SQL column aliases used by this projection for the columns it writes for inclusion into the
+	 * <tt>SELECT</tt> clause ({@link #toSqlString} <i>for a particular criteria-level alias</i>.
+	 *
+	 * @param alias The criteria-level alias
+	 * @param position Just as in {@link #toSqlString}, represents the number of <b>columns</b> rendered
+	 * prior to this projection.
+	 * @return The columns aliases pertaining to a particular criteria-level alias; expected to return null if
+	 * this projection does not understand this alias.
 	 */
-	public String[] getColumnAliases(String alias, int loc);
-	
+	public String[] getColumnAliases(String alias, int position);
+
 	/**
-	 * Get the user-visible aliases for this projection
-	 * (ie. the ones that will be passed to the 
-	 * <tt>ResultTransformer</tt>)
+	 * Get the criteria-level aliases for this projection (ie. the ones that will be passed to the
+	 * {@link org.hibernate.transform.ResultTransformer})
+	 *
+	 * @return The aliases
 	 */
 	public String[] getAliases();
-	
+
 	/**
-	 * Does this projection specify grouping attributes?
+	 * Is this projection fragment (<tt>SELECT</tt> clause) also part of the <tt>GROUP BY</tt>
+	 *
+	 * @return True if the projection is also part of the <tt>GROUP BY</tt>; false otherwise.
 	 */
 	public boolean isGrouped();
-	
+
 }