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/* 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 org.activiti.engine.query;

import java.util.List;

/**
 * Describes basic methods for querying.
 * 
 * @author Frederik Heremans
 */
public interface Query, U extends Object> {

  /**
   * Order the results ascending on the given property as defined in this
   * class (needs to come after a call to one of the orderByXxxx methods).
   */
  T asc();

  /**
   * Order the results descending on the given property as defined in this
   * class (needs to come after a call to one of the orderByXxxx methods).
   */
  T desc();

  /** Executes the query and returns the number of results */
  long count();

  /**
   * Executes the query and returns the resulting entity or null if no
   * entity matches the query criteria.
   * @throws ActivitiException when the query results in more than one
   * entities.
   */
  U singleResult();

  /** Executes the query and get a list of entities as the result. */
  List list();

  /** Executes the query and get a list of entities as the result. */
  List listPage(int firstResult, int maxResults);
}