Java tutorial
/******************************************************************************* * Copyright (c) 2008 - 2013 Oracle Corporation. 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: * Linda DeMichiel - Java Persistence 2.1 * Linda DeMichiel - Java Persistence 2.0 * ******************************************************************************/ package javax.persistence; import java.lang.annotation.Target; import java.lang.annotation.Retention; import static java.lang.annotation.ElementType.TYPE; import static java.lang.annotation.RetentionPolicy.RUNTIME; /** * Specifies the value of the discriminator column for * entities of the given type. * * <p> The <code>DiscriminatorValue</code> * annotation can only be specified on a concrete entity * class. * * <p> If the <code>DiscriminatorValue</code> annotation is not * specified and a discriminator column is used, a provider-specific * function will be used to generate a value representing the * entity type. If the {@link DiscriminatorType} is <code> * STRING</code>, the discriminator value * default is the entity name. * * <p> The inheritance strategy and the discriminator column * are only specified in the root of an entity class hierarchy * or subhierarchy in which a different inheritance strategy is * applied. The discriminator value, if not defaulted, should be * specified for each entity class in the hierarchy. * * <pre> * * Example: * * @Entity * @Table(name="CUST") * @Inheritance(strategy=SINGLE_TABLE) * @DiscriminatorColumn(name="DISC", discriminatorType=STRING, length=20) * @DiscriminatorValue("CUSTOMER") * public class Customer { ... } * * @Entity * @DiscriminatorValue("VCUSTOMER") * public class ValuedCustomer extends Customer { ... } * </pre> * * @see DiscriminatorColumn * * @since Java Persistence 1.0 */ @Target({ TYPE }) @Retention(RUNTIME) public @interface DiscriminatorValue { /** * (Optional) The value that indicates that the * row is an entity of the annotated entity type. * * <p> If the <code>DiscriminatorValue</code> annotation is not * specified and a discriminator column is used, a * provider-specific function will be used to generate a value * representing the entity type. If the <code>DiscriminatorType</code> is * <code>STRING</code>, the discriminator value default is the * entity name. */ String value(); }