Hi Guys,

with hibernate 3.2 RC I used to use detached entities and send them back and forth across the boundary between my ejb layer to my web layer (from session bean to jsf managed bean) like value objects. It worked really well, and I just did an entityManager.refresh(myEntity) before working with it to reattach it.

Now, when I do an entityManager.refresh(myObject) on an object that has previously been persisted by hibernate, but detached to the web layer and sent back to be reattached...it throws the following exception

Caused by: java.lang.IllegalArgumentException: Entity not managed
at org.hibernate.ejb.AbstractEntityManagerImpl.refresh(AbstractEntityManagerImpl.java:260)
at com.sun.enterprise.util.EntityManagerWrapper.refresh(EntityManagerWrapper.java:783)


Which I discovered is related to jira ticket #EJB-205 (http://opensource.atlassian.com/project ... se/EJB-205)

So, my question is...now that you can't use refresh to reattach a detached object, what is the correct way to do it?

Cheers
Adam

....by 'now' I mean 3.2GA

I've just upgraded from 3.2RC2 to 3.2GA

session.lock(, LockMode.NONE) and then em.refresh() will do what you want.
But I don't recommend it for data integrity (neither the way you did it previously).

is there any best practice for detaching entities that you know of anywhere?

...I don't have access to the session...I'm using stock standard ejb3

so

@PersistenceContext
private EntityManager em;

@TransactionAttribute(TransactionAttributeType.REQUIRED)
public int getFriendCount(UserAccount acct){
em.refresh(acct);
return acct.getFriends().size();
}

i don't think "stock standard ejb3" supports reattachment.

you would need to use .merg() first...but not sure that gives the behavior you want.

Is that correct Emmanuel?

yeah, you're right about reattachement. I read a couple of articles and the all say you have to do another find (or, as you say, a merge).

So (from what I can gather) my method really should have been:

@TransactionAttribute(TransactionAttributeType.REQUIRED)
public int getFriendCount(int userAccountId){
UserAccount acct = em.find(UserAccount.class, userAccountId);
return acct.getFriends().size();
}

find() is lighter than merge() for what you want to do.