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package javax.persistence.criteria;

import java.util.List;
import java.util.Set;

import javax.persistence.metamodel.EntityType;

/**
 * The AbstractQuery interface defines functionality that is common to both top-level queries and subqueries. It is not intended to be used
 * directly in query construction.
 * 
 * All queries must have: a set of root entities (which may in turn own joins) All queries may have: a conjunction of restrictions.
 * 
 * @param 
 *            type of the result
 */
public interface AbstractQuery {
	/**
	 * 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.
	 * 
	 * @param distinct
	 *            boolean value specifying whether duplicate results must be eliminated from the query result or whether they must be
	 *            retained
	 * @return the modified query
	 */
	AbstractQuery distinct(boolean distinct);

	/**
	 * Create and add a query root corresponding to the given entity, forming a cartesian product with any existing roots.
	 * 
	 * @param entityClass
	 *            the entity class
	 * @param 
	 *            The type of the represented object
	 * @return query root corresponding to the given entity
	 */
	 Root from(Class entityClass);

	/**
	 * Create and add a query root corresponding to the given entity, forming a cartesian product with any existing roots.
	 * 
	 * @param entity
	 *            metamodel entity representing the entity of type X
	 * @param 
	 *            The type of the represented object
	 * @return query root corresponding to the given entity
	 */
	 Root from(EntityType entity);

	/**
	 * Return a list of the grouping expressions. Returns empty list if no grouping expressions have been specified. Modifications to the
	 * list do not affect the query.
	 * 
	 * @return the list of grouping expressions
	 */
	List> getGroupList();

	/**
	 * Return the predicate that corresponds to the restriction(s) over the grouping items, or null if no restrictions have been specified.
	 * 
	 * @return having clause predicate
	 */
	Predicate getGroupRestriction();

	/**
	 * Return the predicate that corresponds to the where clause restriction(s), or null if no restrictions have been specified.
	 * 
	 * @return where clause predicate
	 */
	Predicate getRestriction();

	/**
	 * Return the result type of the query or subquery. If a result type was specified as an argument to the createQuery or subquery method,
	 * that type will be returned. If the query was created using the createTupleQuery method, the result type is Tuple. Otherwise, the
	 * result type is Object.
	 * 
	 * @return result type
	 */
	Class getResultType();

	/**
	 * Return the query roots. These are the roots that have been defined for the CriteriaQuery or Subquery itself, including any subquery
	 * roots defined as a result of correlation. Returns empty set if no roots have been defined. Modifications to the set do not affect the
	 * query.
	 * 
	 * @return the set of query roots
	 */
	Set> getRoots();

	/**
	 * Return the selection of the query, or null if no selection has been set.
	 * 
	 * @return selection item
	 */
	Selection getSelection();

	/**
	 * Specify the expressions that are used to form groups over the query results. Replaces the previous specified grouping expressions, if
	 * any. If no grouping expressions are specified, any previously added grouping expressions are simply removed.
	 * 
	 * @param grouping
	 *            zero or more grouping expressions
	 * @return the modified query
	 */
	AbstractQuery groupBy(Expression... grouping);

	/**
	 * Specify the expressions that are used to form groups over the query results. Replaces the previous specified grouping expressions, if
	 * any. If no grouping expressions are specified, any previously added grouping expressions are simply removed.
	 * 
	 * @param grouping
	 *            list of zero or more grouping expressions
	 * @return the modified query
	 */
	AbstractQuery groupBy(List> grouping);

	/**
	 * Specify a restriction over the groups of the query. Replaces the previous having restriction(s), if any.
	 * 
	 * @param restriction
	 *            a simple or compound boolean expression
	 * @return the modified query
	 */
	AbstractQuery having(Expression restriction);

	/**
	 * Specify restrictions over the groups of the query according the conjunction of the specified restriction predicates. Replaces the
	 * previously added having restriction(s), if any. If no restrictions are specified, any previously added restrictions are simply
	 * removed.
	 * 
	 * @param restrictions
	 *            zero or more restriction predicates
	 * @return the modified query
	 */
	AbstractQuery having(Predicate... restrictions);

	/**
	 * Return whether duplicate query results must be eliminated or retained.
	 * 
	 * @return boolean indicating whether duplicate query results must be eliminated
	 */
	boolean isDistinct();

	/**
	 * Create a subquery of the query.
	 * 
	 * @param type
	 *            the subquery result type
	 * @param 
	 *            The type of the represented object
	 * @return subquery
	 */
	 Subquery subquery(Class type);

	/**
	 * Modify the query to restrict the query results according to the specified boolean expression. Replaces the previously added
	 * restriction(s), if any.
	 * 
	 * @param restriction
	 *            a simple or compound boolean expression
	 * @return the modified query
	 */
	AbstractQuery where(Expression restriction);

	/**
	 * Modify the query to restrict the query results 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.
	 * 
	 * @param restrictions
	 *            zero or more restriction predicates
	 * @return the modified query
	 */
	AbstractQuery where(Predicate... restrictions);
}