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/*
 * Copyright 2010 Bull S.A.S.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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
 * @see JPA 2.0 specification
 * @author Florent Benoit
 * @since JPA 2.0 version.
 */
public interface AbstractQuery {
    /**
     * Create and add a query root corresponding to the given entity,
     * forming a cartesian product with any existing roots.
     * @param entityClass the entity class
     * @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
     * @return query root corresponding to the given entity
     */
     Root from(EntityType entity);
    /**
     * 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);

    /**
     * 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);
    /**
     * 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 a subquery of the query.
     * @param type the subquery result type
     * @return subquery
     */
     Subquery subquery(Class type);
    /**
     * 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();
    /**
     * 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 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 whether duplicate query results must be eliminated or
     * retained.
     * @return boolean indicating whether duplicate query results
     *         must be eliminated
     */
    boolean isDistinct();

    /**
     * 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();
}