Question

Environment:

I have that User entity :

@Entity
public class User implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer userId;

    @Version
    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "VERSION", length = 19)
    private Date version;

    @Column(nullable = false, length = 20)
    private String login;

    // Getters and Setters
}

I have a search page which lists users, then I click on a user to edit it (giving its userId in the URL).

In the edit form, I store on the server the fields of that entity and when I save my User I do this :

User user = entityManager.find(User.class, userId)
user.setLogin(form.getLogin());
user.setVersion(form.getVersion());
user.setUserId(form.getUserId());
entityManager.merge(user);

Question:

So if I correctly understood optimistic locking with Hibernate, if I open 2 tabs in my browser to edit the same user, then update the login on the first tab, and then the login on the second tab, I should have an OptimisticLockException shouldn’t I ?

Actually, this is not the case on my application… I verified, the form.getVersion() return the same value in both case, even if that in the second update, the user.version has been updated by the first edit.

Am I missing something ?

The EntityManager is produced @RequestScoped (so I’m on two different EntityManagers when I try to merge…).

I’ve tried to do a entityManager.lock(user, LockModeType.OPTIMISTIC_FORCE_INCREMENT) before entityManager.merge(...) (as said here), but it didn’t help.

I’m using Seam 3 with JBoss 7.0.2.Final (which uses Hibernate 4).

Answer 1

Actually I’ve found a way to do that… but I think it’s not really efficient (because there is 1 more SELECT request).

User user = entityManager.find(User.class, userId)
user.setLogin(form.getLogin());
user.setVersion(form.getVersion());
user.setUserId(form.getUserId());

entityManager.detach(user);
entityManager.merge(user);

With entityManager.detach(user), hibernate now uses my setted version value instead of its own copied somewhere value…