src/javax/persistence/criteria/Subquery.java

/*******************************************************************************
 * Copyright (c) 1998, 2009 Oracle. All rights reserved. 
 * 
 * This program and the accompanying materials are made available under the 
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 
 * which accompanies this distribution. 
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at 
 * http://www.eclipse.org/org/documents/edl-v10.php.
 * 
 * Contributors:
 *     dclarke - Java Persistence 2.0 - Proposed Final Draft (March 13, 2009)
 *     		     Specification available from http://jcp.org/en/jsr/detail?id=317
 *
 * Java(TM) Persistence API, Version 2.0 - EARLY ACCESS
 * This is an implementation of an early-draft specification developed under the 
 * Java Community Process (JCP).  The code is untested and presumed not to be a  
 * compatible implementation of JSR 317: Java(TM) Persistence API, Version 2.0.   
 * We encourage you to migrate to an implementation of the Java(TM) Persistence 
 * API, Version 2.0 Specification that has been tested and verified to be compatible 
 * as soon as such an implementation is available, and we encourage you to retain 
 * this notice in any implementation of Java(TM) Persistence API, Version 2.0 
 * Specification that you distribute.
 ******************************************************************************/
package javax.persistence.criteria;

/**
 * The interface Subquery defines functionality that is specific to subqueries.
 * 
 * A subquery has an expression as its selection item.
 * 
 * @param <T>
 *            the type of the returned selection item.
 *            
 * @since Java Persistence 2.0
 */
public interface Subquery<T> extends AbstractQuery<T>, Expression<T> {
	
    /**
     * Specify the item that is to be returned in the query result. Replaces the
     * previously specified selection, if any.
     * 
     * @param expression
     *            expression specifying the item that is returned in the query
     *            result
     * @return the modified subquery
     */
    Subquery<T> select(Expression<T> expression);

    // override the return type only:
    /**
     * Modify the subquery to restrict the result according to the specified
     * boolean expression. Replaces the previously added restriction(s), if any.
     * This method only overrides the return type of the corresponding
     * AbstractQuery method.
     * 
     * @param restriction
     *            a simple or compound boolean expression
     * @return the modified subquery
     */
    Subquery<T> where(Expression<Boolean> restriction);

    /**
     * Modify the subquery to restrict the result according to the conjunction
     * of the specified restriction predicates. Replaces the previously added
     * restriction(s), if any. If no restrictions are specified, any previously
     * added restrictions are simply removed. This method only overrides the
     * return type of the corresponding AbstractQuery method.
     * 
     * @param restrictions
     *            zero or more restriction predicates
     * @return the modified subquery
     */
    Subquery<T> where(Predicate... restrictions);

    /**
     * Specify the expressions that are used to form groups over the subquery
     * results. Replaces the previous specified grouping expressions, if any. If
     * no grouping expressions are specified, any previously added grouping
     * expressions are simply removed. This method only overrides the return
     * type of the corresponding AbstractQuery method.
     * 
     * @param grouping
     *            zero or more grouping expressions
     * @return the modified subquery
     */
    Subquery<T> groupBy(Expression<?>... grouping);

    /**
     * Specify a restriction over the groups of the subquery. Replaces the
     * previous having restriction(s), if any. This method only overrides the
     * return type of the corresponding AbstractQuery method.
     * 
     * @param restriction
     *            a simple or compound boolean expression
     * @return the modified subquery
     */
    Subquery<T> having(Expression<Boolean> restriction);

    /**
     * Specify restrictions over the groups of the subquery according the
     * conjunction of the specified restriction predicates. Replaces the
     * previously added restriction(s), if any. If no restrictions are
     * specified, any previously added restrictions are simply removed. This
     * method only overrides the return type of the corresponding AbstractQuery
     * method.
     * 
     * @param restrictions
     *            zero or more restriction predicates
     * @return the modified subquery
     */
    Subquery<T> having(Predicate... restrictions);

    /**
     * Specify whether duplicate query results will be eliminated. A true value
     * will cause duplicates to be eliminated. A false value will cause
     * duplicates to be retained. If distinct has not been specified, duplicate
     * results must be retained. This method only overrides the return type of
     * the corresponding AbstractQuery method.
     * 
     * @param distinct
     *            boolean value specifying whether duplicate results must be
     *            eliminated from the subquery result or whether they must be
     *            retained
     * @return the modified subquery.
     */
    Subquery<T> distinct(boolean distinct);

    /**
     * Return the selection expression.
     * 
     * @return the item to be returned in the subquery result
     */
    Expression<T> getSelection();

    /**
     * Correlates a root of the enclosing query to a root of the subquery and
     * returns the subquery root.
     * 
     * @param parentRoot
     *            a root of the containing query
     * @return subquery root
     */
    <Y> Root<Y> correlate(Root<Y> parentRoot);

    /**
     * Correlates a join object of the enclosing query to a join object of the
     * subquery and returns the subquery join object.
     * 
     * @param parentJoin
     *            join target of the containing query
     * @return subquery join
     */
    <X, Y> Join<X, Y> correlate(Join<X, Y> parentJoin);

    /**
     * Correlates a join to a Collection-valued association or element
     * collection in the enclosing query to a join object of the subquery and
     * returns the subquery join object.
     * 
     * @param parentCollection
     *            join target of the containing query
     * @return subquery join
     */
    <X, Y> CollectionJoin<X, Y> correlate(CollectionJoin<X, Y> parentCollection);

    /**
     * Correlates a join to a Set-valued association or element collection in
     * the enclosing query to a join object of the subquery and returns the
     * subquery join object.
     * 
     * @param parentSet
     *            join target of the containing query
     * @return subquery join
     */
    <X, Y> SetJoin<X, Y> correlate(SetJoin<X, Y> parentSet);

    /**
     * Correlates a join to a List-valued association or element collection in
     * the enclosing query to a join object of the subquery and returns the
     * subquery join object.
     * 
     * @param parentList
     *            join target of the containing query
     * @return subquery join
     */
    <X, Y> ListJoin<X, Y> correlate(ListJoin<X, Y> parentList);

    /**
     * Correlates a join to a Map-valued association or element collection in
     * the enclosing query to a join object of the subquery and returns the
     * subquery join object.
     * 
     * @param parentMap
     *            join target of the containing query
     * @return subquery join
     */
    <X, K, V> MapJoin<X, K, V> correlate(MapJoin<X, K, V> parentMap);

    /**
     * Return the query of which this is a subquery.
     * @return the enclosing query or subquery
     */
    AbstractQuery<?> getParent();
	
    /**
     * Return the joins that have been made from the subquery.
     * 
     * @return joins made from this type
     */
    java.util.Set<Join<?, ?>> getJoins();
}