https://github.com/javaee/jpa-spec: Java(TM) Persistence API 
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

/*******************************************************************************
 * 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.METHOD;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;


Specifies the version field or property of an entity class that
serves as its optimistic lock value.  The version is used to ensure
integrity when performing the merge operation and for optimistic
concurrency control.

 Only a single Version property or field 
should be used per class; applications that use more than one 
Version property or field will not be portable. 

 The Version property should be mapped to 
the primary table for the entity class; applications that 
map the Version property to a table other than 
the primary table will not be portable.

 The following types are supported for version properties: 
int, Integer, short, 
Short, long, Long, 
java.sql.Timestamp.

   Example:
   @Version
   @Column(name="OPTLOCK")
   protected int getVersionNum() { return versionNum; }



Since:Java Persistence 1.0
/**
 * Specifies the version field or property of an entity class that
 * serves as its optimistic lock value.  The version is used to ensure
 * integrity when performing the merge operation and for optimistic
 * concurrency control.
 *
 * <p> Only a single <code>Version</code> property or field 
 * should be used per class; applications that use more than one 
 * <code>Version</code> property or field will not be portable. 
 * 
 * <p> The <code>Version</code> property should be mapped to 
 * the primary table for the entity class; applications that 
 * map the <code>Version</code> property to a table other than 
 * the primary table will not be portable.
 * 
 * <p> The following types are supported for version properties: 
 * <code>int</code>, <code>Integer</code>, <code>short</code>, 
 * <code>Short</code>, <code>long</code>, <code>Long</code>, 
 * <code>java.sql.Timestamp</code>.
 *
 * <pre>
 *    Example:
 *
 *    &#064;Version
 *    &#064;Column(name="OPTLOCK")
 *    protected int getVersionNum() { return versionNum; }
 * </pre>
 *
 * @since Java Persistence 1.0
 */
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface Version {}