help with optimistic locking

balamg Aug 1, 2006 3:22 AM

I have an entity bean on these lines..

@Entity
User {
@Version int version;

@Id String id;

...
...
}

Then I have a SLSB with this method:

updateUser (User u) {
@PersistenceContext
EntityManager em;

List dbUsers = em.createQuery("select from User u where u.name = 'user1').getResultList();
User dbUser = dbUsers.get(0);

dbUser.setName("user2");

}

i would have expected the version count of the user to be incremented. this does not happen.

Then i tried with the following
em.lock(dbUser, LockModeType.READ);
and also em.lock(dbUser,LockModeType.WRITE);
before the setter method.

still the version does not get updated.

What am i doing wrong here..

1. Re: help with optimistic locking

balamg Aug 1, 2006 4:40 AM (in response to balamg)

Furhter debugging resulted in this observation:

in other than lockmode=write, the transaction gets committed.

in the lockmode=write, this is what is happening:

java.lang.NullPointerException
2006-08-01 13:34:58,765 ERROR [STDERR] at org.hibernate.persister.entity.AbstractEntityPersister.lock(AbstractEntityPersister.java:1282)
2006-08-01 13:34:58,765 ERROR [STDERR] at org.hibernate.event.def.AbstractLockUpgradeEventListener.upgradeLock(AbstractLockUpgradeEventListener.java:88)
2006-08-01 13:34:58,765 ERROR [STDERR] at org.hibernate.event.def.DefaultLockEventListener.onLock(DefaultLockEventListener.java:64)
2006-08-01 13:34:58,765 ERROR [STDERR] at org.hibernate.impl.SessionImpl.fireLock(SessionImpl.java:586)
2006-08-01 13:34:58,765 ERROR [STDERR] at org.hibernate.impl.SessionImpl.lock(SessionImpl.java:578)
2006-08-01 13:34:58,765 ERROR [STDERR] at org.hibernate.ejb.AbstractEntityManagerImpl.lock(AbstractEntityManagerImpl.java:337)
2006-08-01 13:34:58,765 ERROR [STDERR] at org.jboss.ejb3.entity.TransactionScopedEntityManager.lock(TransactionScopedEntityManager.java:101)

any known workarounds ? fixes ? patches or is it a wrong usage ?

Thank You
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