/*
 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. 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.
 */
package javax.persistence;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.RetentionPolicy.RUNTIME;

Used in conjunction with the SqlResultSetMapping annotation to map the SELECT clause of a SQL query to a constructor. 
 Applies a constructor for the target class, passing in as arguments values from the specified columns. All columns corresponding to arguments of the intended constructor must be specified using the columns element of the ConstructorResult annotation in the same order as that of the argument list of the constructor. Any entities returned as constructor results will be in either the new or detached state, depending on whether a primary key is retrieved for the constructed object. 

Example:

    Query q = em.createNativeQuery(
    		"SELECT c.id, c.name, COUNT(o) as orderCount, AVG(o.price) AS avgOrder " +
    			"FROM Customer c, Orders o " +
    			"WHERE o.cid = c.id " +
    			"GROUP BY c.id, c.name",
    		"CustomerDetailsResult"
   );
   @SqlResultSetMapping(
   		name="CustomerDetailsResult",
   		classes = {
   			@ConstructorResult(
   				targetClass=com.acme.CustomerDetails.class,
   				columns={
   					@ColumnResult(name="id"),
   					@ColumnResult(name="name"),
   					@ColumnResult(name="orderCount"),
   					@ColumnResult(name="avgOrder", type=Double.class)
   			    }
   		    )
   		}

/**
 * Used in conjunction with the {@link SqlResultSetMapping} annotation to map the SELECT clause of a SQL query
 * to a constructor.
 * <p/>
 * Applies a constructor for the target class, passing in as arguments values from the specified columns. All
 * columns corresponding to arguments of the intended constructor must be specified using the {@code columns}
 * element of the {@code ConstructorResult} annotation in the same order as that of the argument list of the
 * constructor. Any entities returned as constructor results will be in either the new or detached state,
 * depending on whether a primary key is retrieved for the constructed object.
 * <p/>
 * Example:
 * <p>
 * <pre>
 *     Query q = em.createNativeQuery(
 *     		"SELECT c.id, c.name, COUNT(o) as orderCount, AVG(o.price) AS avgOrder " +
 *     			"FROM Customer c, Orders o " +
 *     			"WHERE o.cid = c.id " +
 *     			"GROUP BY c.id, c.name",
 *     		"CustomerDetailsResult"
 *    );
 *
 *    @SqlResultSetMapping(
 *    		name="CustomerDetailsResult",
 *    		classes = {
 *    			@ConstructorResult(
 *    				targetClass=com.acme.CustomerDetails.class,
 *    				columns={
 *    					@ColumnResult(name="id"),
 *    					@ColumnResult(name="name"),
 *    					@ColumnResult(name="orderCount"),
 *    					@ColumnResult(name="avgOrder", type=Double.class)
 *    			    }
 *    		    )
 *    		}
 * </pre>
 */
@Target(value = {})
@Retention(RUNTIME)
public @interface ConstructorResult {
  
(Required) The class whose constructor is to be invoked.
Returns:
target class/**
   * (Required) The class whose constructor is to be invoked.
   *
   * @return target class
   */
  Class targetClass();

  
(Required) The mapping of columns in the SELECT list to the arguments of the intended constructor, in
order.
Returns:
columns/**
   * (Required) The mapping of columns in the SELECT list to the arguments of the intended constructor, in
   * order.
   *
   * @return columns
   */
  ColumnResult[] columns();
}