JPA: How to implement Versioning (@Version)

In another article I will explain what versioning is and differences between optimistic and pessimistic versioning. Here I will just describe how to implement optimistic versioning it..

@Entity
public class Foo {
 // ...

 prive Long version;
 @Version
 public Long getVersion() { return version; }
 public void setVersion(Long version) { this.version = version; }

 // ...
}

On each transaction commit if the entity is modified (persist or merge) the version column is increased by one.

Other possibilities

Instead of a Long you could use a Integer or a Date..but Date has performance problems and does not guarantee good behavior if two commits are happened with milliseconds time difference (see http://swinbrain.ict.swin.edu.au/wiki/Implementing_Concurrency_Controls_using_Hibernate).

See also...

If you get StaleObjectStateException or OptimisticLockException then make sure that you don't persist the loading time of the entity (see http://micharg.blogspot.com/2012/02/jpaversioning-thrown.html)
How to catch a OptimisticLockException