http://hibernate.org: The core O/RM functionality as provided by Hibernate (Hibernate.org) 
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 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, 2013, Red Hat Inc. or third-party contributors as
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 * Lesser General Public License, as published by the Free Software Foundation.
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 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
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package org.hibernate.criterion;

import org.hibernate.type.Type;


The criterion package may be used by applications as a framework for building
new kinds of Projection. However, it is intended that most applications will simply use the built-in projection types via the static factory methods of this class. The factory methods that take an alias allow the projected value to be referred to by criterion and order instances. See also the Restrictions factory methods for generating Criterion instances 
Author:Gavin King, Steve Ebersole
See Also:
/**
 * The <tt>criterion</tt> package may be used by applications as a framework for building
 * new kinds of <tt>Projection</tt>. However, it is intended that most applications will
 * simply use the built-in projection types via the static factory methods of this class.
 *
 * The factory methods that take an alias allow the projected value to be referred to by 
 * criterion and order instances.
 *
 * See also the {@link Restrictions} factory methods for generating {@link Criterion} instances
 *
 * @author Gavin King
 * @author Steve Ebersole
 *
 * @see org.hibernate.Criteria
 */
public final class Projections {
	
A property value projection

Params:
  • propertyName – The name of the property whose values should be projected
See Also:
Returns:The property projection
/**
	 * A property value projection
	 *
	 * @param propertyName The name of the property whose values should be projected
	 *
	 * @return The property projection
	 *
	 * @see PropertyProjection
	 */
	public static PropertyProjection property(String propertyName) {
		return new PropertyProjection( propertyName );
	}

	
A grouping property value projection

Params:
  • propertyName – The name of the property to group
See Also:
Returns:The grouped projection
/**
	 * A grouping property value projection
	 *
	 * @param propertyName The name of the property to group
	 *
	 * @return The grouped projection
	 *
	 * @see PropertyProjection
	 */
	public static PropertyProjection groupProperty(String propertyName) {
		return new PropertyProjection( propertyName, true );
	}

	
An identifier value projection.

See Also:
Returns:The identifier projection
/**
	 * An identifier value projection.
	 *
	 * @return The identifier projection
	 *
	 * @see IdentifierProjection
	 */
	public static IdentifierProjection id() {
		return new IdentifierProjection();
	}

	
Create a distinct projection from a projection.

Params:
  • projection – The project to treat distinctly
See Also:
Returns:The distinct projection
/**
	 * Create a distinct projection from a projection.
	 *
	 * @param projection The project to treat distinctly
	 *
	 * @return The distinct projection
	 *
	 * @see Distinct
	 */
	public static Projection distinct(Projection projection) {
		return new Distinct( projection );
	}
	
	
Create a new projection list.

Returns:The projection list
/**
	 * Create a new projection list.
	 *
	 * @return The projection list
	 */
	public static ProjectionList projectionList() {
		return new ProjectionList();
	}
		
	
The query row count, ie. count(*)

See Also:
Returns:The projection representing the row count
/**
	 * The query row count, ie. <tt>count(*)</tt>
	 *
	 * @return The projection representing the row count
	 *
	 * @see RowCountProjection
	 */
	public static Projection rowCount() {
		return new RowCountProjection();
	}
	
	
A property value count projection

Params:
  • propertyName – The name of the property to count over
See Also:
Returns:The count projection
/**
	 * A property value count projection
	 *
	 * @param propertyName The name of the property to count over
	 *
	 * @return The count projection
	 *
	 * @see CountProjection
	 */
	public static CountProjection count(String propertyName) {
		return new CountProjection( propertyName );
	}
	
	
A distinct property value count projection

Params:
  • propertyName – The name of the property to count over
See Also:
Returns:The count projection
/**
	 * A distinct property value count projection
	 *
	 * @param propertyName The name of the property to count over
	 *
	 * @return The count projection
	 *
	 * @see CountProjection
	 */
	public static CountProjection countDistinct(String propertyName) {
		return new CountProjection( propertyName ).setDistinct();
	}
	
	
A property maximum value projection

Params:
  • propertyName – The property for which to find the max
See Also:
Returns:the max projection
/**
	 * A property maximum value projection
	 *
	 * @param propertyName The property for which to find the max
	 *
	 * @return the max projection
	 *
	 * @see AggregateProjection
	 */
	public static AggregateProjection max(String propertyName) {
		return new AggregateProjection( "max", propertyName );
	}
	
	
A property minimum value projection

Params:
  • propertyName – The property for which to find the min
See Also:
Returns:the min projection
/**
	 * A property minimum value projection
	 *
	 * @param propertyName The property for which to find the min
	 *
	 * @return the min projection
	 *
	 * @see AggregateProjection
	 */
	public static AggregateProjection min(String propertyName) {
		return new AggregateProjection( "min", propertyName );
	}
	
	
A property average value projection

Params:
  • propertyName – The property over which to find the average
See Also:
Returns:the avg projection
/**
	 * A property average value projection
	 *
	 * @param propertyName The property over which to find the average
	 *
	 * @return the avg projection
	 *
	 * @see AvgProjection
	 */
	public static AggregateProjection avg(String propertyName) {
		return new AvgProjection( propertyName );
	}
	
	
A property value sum projection

Params:
  • propertyName – The property over which to sum
See Also:
Returns:the sum projection
/**
	 * A property value sum projection
	 *
	 * @param propertyName The property over which to sum
	 *
	 * @return the sum projection
	 *
	 * @see AggregateProjection
	 */
	public static AggregateProjection sum(String propertyName) {
		return new AggregateProjection( "sum", propertyName );
	}
	
	
Assign an alias to a projection, by wrapping it

Params:
  • projection – The projection to be aliased
  • alias – The alias to apply
See Also:
Returns:The aliased projection
/**
	 * Assign an alias to a projection, by wrapping it
	 *
	 * @param projection The projection to be aliased
	 * @param alias The alias to apply
	 *
	 * @return The aliased projection
	 *
	 * @see AliasedProjection
	 */
	public static Projection alias(Projection projection, String alias) {
		return new AliasedProjection( projection, alias );
	}

	
A SQL projection, a typed select clause fragment

Params:
  • sql – The SQL fragment
  • columnAliases – The column aliases
  • types – The resulting types
See Also:
Returns:The SQL projection
/**
	 * A SQL projection, a typed select clause fragment
	 *
	 * @param sql The SQL fragment
	 * @param columnAliases The column aliases
	 * @param types The resulting types
	 *
	 * @return The SQL projection
	 *
	 * @see SQLProjection
	 */
	public static Projection sqlProjection(String sql, String[] columnAliases, Type[] types) {
		return new SQLProjection( sql, columnAliases, types );
	}

	
A grouping SQL projection, specifying both select clause and group by clause fragments

Params:
  • sql – The SQL SELECT fragment
  • groupBy – The SQL GROUP BY fragment
  • columnAliases – The column aliases
  • types – The resulting types
See Also:
Returns:The SQL projection
/**
	 * A grouping SQL projection, specifying both select clause and group by clause fragments
	 *
	 * @param sql The SQL SELECT fragment
	 * @param groupBy The SQL GROUP BY fragment
	 * @param columnAliases The column aliases
	 * @param types The resulting types
	 *
	 * @return The SQL projection
	 *
	 * @see SQLProjection
	 */
	@SuppressWarnings("UnusedDeclaration")
	public static Projection sqlGroupProjection(String sql, String groupBy, String[] columnAliases, Type[] types) {
		return new SQLProjection(sql, groupBy, columnAliases, types);
	}

	private Projections() {
		//cannot be instantiated
	}

}