001/*
002 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. All rights reserved.
003 *
004 * This program and the accompanying materials are made available under the
005 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
006 * which accompanies this distribution.  The Eclipse Public License is available
007 * at http://www.eclipse.org/legal/epl-v10.html and the Eclipse Distribution License
008 * is available at http://www.eclipse.org/org/documents/edl-v10.php.
009 */
010package javax.persistence;
011
012import java.lang.annotation.Retention;
013import java.lang.annotation.Target;
014
015import static java.lang.annotation.ElementType.FIELD;
016import static java.lang.annotation.RetentionPolicy.RUNTIME;
017
018/**
019 * Specifies the version field or property of an entity class that
020 * serves as its optimistic lock value.  The version is used to ensure
021 * integrity when performing the merge operation and for optimistic
022 * concurrency control.
023 * <p>
024 * <p> Only a single <code>Version</code> property or field
025 * should be used per class; applications that use more than one
026 * <code>Version</code> property or field will not be portable.
027 * <p>
028 * <p> The <code>Version</code> property should be mapped to
029 * the primary table for the entity class; applications that
030 * map the <code>Version</code> property to a table other than
031 * the primary table will not be portable.
032 * <p>
033 * <p> The following types are supported for version properties:
034 * <code>int</code>, <code>Integer</code>, <code>short</code>,
035 * <code>Short</code>, <code>long</code>, <code>Long</code>,
036 * <code>java.sql.Timestamp</code>.
037 * <p>
038 * <pre>
039 *    Example:
040 *
041 *    &#064;Version
042 *    int version;
043 * </pre>
044 *
045 * @since Java Persistence 1.0
046 */
047@Target({FIELD})
048@Retention(RUNTIME)
049public @interface Version {
050}