| /* |
| * Copyright (c) 2011, 2020 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 v. 2.0 which is available at |
| * http://www.eclipse.org/legal/epl-2.0, |
| * or the Eclipse Distribution License v. 1.0 which is available at |
| * http://www.eclipse.org/org/documents/edl-v10.php. |
| * |
| * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause |
| */ |
| |
| // 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(); |
| } |
| |