| /*******************************************************************************
|
| * Copyright (c) 2011, 2014 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 org.eclipse.persistence.expressions.Expression; |
| |
| 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(); |
| }
|
|
|