/******************************************************************************* | |
* Copyright (c) 2011, 2013 Oracle and/or its affiliates. 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. | |
* | |
* Contributors: | |
* 12/18/2009-2.1 Guy Pelletier | |
* - 211323: Add class extractor support to the EclipseLink-ORM.XML Schema | |
******************************************************************************/ | |
package org.eclipse.persistence.annotations; | |
import java.lang.annotation.Retention; | |
import java.lang.annotation.Target; | |
import static java.lang.annotation.ElementType.TYPE; | |
import static java.lang.annotation.RetentionPolicy.RUNTIME; | |
/** | |
* A ClassExtractor allows for a user defined class indicator in place of | |
* providing a discriminator column. The class has the following restrictions: | |
* <ul> | |
* <li> It must extend the org.eclipse.persistence.descriptors.ClassExtractor | |
* class and implement the extractClassFromRow(Record, Session) method. | |
* <li> That method must take a database row (a Record/Map) as an argument and | |
* must return the class to use for that row. | |
* </ul> | |
* This method will be used to decide which class to instantiate when reading | |
* from the database. It is the application's responsibility to populate any | |
* typing information in the database required to determine the class from the | |
* row. | |
* <p> | |
* The ClassExtractor must only be set on the root of an entity class or | |
* sub-hierarchy in which a different inheritance strategy is applied. The | |
* ClassExtractor can only be used with the SINGLE_TABLE and JOINED inheritance | |
* strategies. | |
* <p> | |
* If a ClassExtractor is used then a DiscriminatorColumn cannot be used. A | |
* DiscriminatorColumn also cannot be used on either the root or its subclasses. | |
* <p> | |
* In addition, for more complex configurations using a ClassExtractor and a | |
* SINGLE_TABLE strategy, the descriptor's withAllSubclasses and onlyInstances | |
* expressions should be set through the ClassExtractor's initialize method. | |
* | |
* @see org.eclipse.persistence.descriptors.ClassExtractor | |
* @see org.eclipse.persistence.descriptors.InheritancePolicy.setWithAllSubclassesExpression(Expression) | |
* @see org.eclipse.persistence.descriptors.InheritancePolicy.setOnlyInstancesExpression(Expression) | |
* | |
* @author Guy Pelletier | |
* @since EclipseLink 2.1 | |
*/ | |
@Target({TYPE}) | |
@Retention(RUNTIME) | |
public @interface ClassExtractor { | |
/** | |
* (Required) Defines the name of the class extractor that should be | |
* applied to this entity's descriptor. | |
*/ | |
Class<? extends org.eclipse.persistence.descriptors.ClassExtractor> value(); | |
} | |