javax.persistence.ConstructorResult Maven / Gradle / Ivy

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/*
 * 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 {@link 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 {@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.
 * 

 * 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)
 *    			    }
 *    		    )
 *    		}
 * 
 */
@Target(value = {})
@Retention(RUNTIME)
public @interface ConstructorResult {
  /**
   * (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.
   *
   * @return columns
   */
  ColumnResult[] columns();
}