Long running conversations and entity managers, a bit confus

[andrew.rw.robinson]

Okay, I am a bit confused how the EJB3 session beans + Seam + Seam managed entity managers work. I have looked at the examples, and none seem to do this.

What I am doing:
I am creating a registration site for a conference. The registration process is a wizard invovling 3-x number of steps. On the first step, I am creating a Registration object and adding it to my Conference object (collections mapped via one-to-many). The registration has several children objects called BreakoutSessionRegistration, and the Conference has several children of type BreakoutSession.

On the beginRegistration:

@Begin(join=true)
 @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
 public String beginRegistration()
 {
 this.registration = new Registration();
 this.registration.setConference(conference);
 this.conference.getRegistrations().add(registration);
 for (BreakoutSession bs : this.conference.getBreakoutSessions())
 {
 BreakoutSessionRegistration bsr = new BreakoutSessionRegistration();
 bsr.setRegistration(registration);
 bsr.setSession(bs);
 bsr.setNumberOfAttendees((short)0);
 bsr.getRegistration().getBreakoutRegistrations().add(bsr);
 bsr.getSession().getRegistrations().add(bsr);
 }

 return "beginRegistration";
 }

So now, I want the user to continue to edit this registration object and breakout sessions over several pages of a wizard.

I also want to have a cancel button:

 @End
 public String cancel()
 {
 // what to do here?
 return "canceled";
 }

I don't want anything committed to the database until my save() method is called. I also want the cancel button to undo its changes. In this same "action" class, I have a list of all the registrations for the current user and a list of all the conferences. I get this list before I ever being a conversation.

My beginRegistration method starts the conversation. The problem is that the conversation is dirty and therefore so is the list of my conversations. When the user cancels, I want to restore the "virgin" state of the conferences and registrations.

Is this possible? I tried entityManager.refresh(Object) on the conference, but it did not like the fact that the registration was not in the database (null identifier error).

I'm really having a hard time with getting a good grasp of how to use the extended persistence manager, long running conversations and the ability to cancel or save.

Thanks in advance, I'm really at a loss.
Andrew

[gavin.king]

The issue tracker example uses this, actually.

[gavin.king]

Oh, I re-read your question.

You want to avoid flushing, is it?

There are two ways:
(1) use NOT_SUPPORTED on all methods
(2) set FlushMode.NEVER (hibernate-specific)

There is no object-level rollback. clear() the EntityManager and start again.

[andrew.rw.robinson]

is NOT_SUPPORTED on all methods the same as putting it on the class and then marking certain methods as REQUIRED?

[gavin.king]

yes

[andrew.rw.robinson]

Thanks as always Gavin. One more question if you don't mind. If I am using this method, it begs the question why use session beans at all? POJOs would be easier (no interface to maintain). Then the combination would be POJO + EJB3 entities. This pattern would be easier and yet still use EJB3 instead of hibernate for persistence since that is more the "standard" now.

The question I have, is if an EntityManager can be used with POJOs?

@Name("pojo")
public class POJO {
@In(create=true)
private EntityManager entityManager;

[gavin.king]

Well, in the last operatipon of the conversation, you *do* need a txn, in order to flush the pc inside a tx.

So you are going to have one method where you want a declarative txn.

Also, I am kindof a fan of ejb method-level security.