Hi,

In our project we are using a mix of both CMT and BMT stateless session beans. Previously we were using entity beans for persisting the data and now I've removed all the entity beans from the system.

For intergrating the hibernate with the app server(JBoss) I'm using the "HibernateSession" class provided by steve (http://forum.hibernate.org/viewtopic.php?p=504). It is working perfectly for all the Container Managed Transaction beans.

However, for the BMT beans, when I use the "HibernateSession", during closing the session an error is thrown saying



Here's the piece of the code that manages the transactions in EJB for BMT case.




I have also tried to change the above code something like



In that case also I'm getting the same exception.

The transaction attribute for the methods are in the "Supports" level. (I have also changed this to "Required" level, but no use).

Can anybody please explain me how to use hibernate with BMT session beans?

I'm using JBoss 3.0.3 and Hibernate 2.1 r2.

Regards,
Balakrishnan.

That version of thread local session is specifically meant for use in CMT session beans.


I don't understand... The first part of that quote is describing CMT sematics. BMT beans cannot have transaction attributes set, as it is the job of the bean itself, not the container, to maintain transactions. Can you clarify what you mean here?

I never use BMT, as I don't see the point (but thats just me). But if you plan on continued use of BMT, then I'd say to close the session prior to commiting the transaction. You would probably even want to come up with another version of HibernateSession to use in those situations just because the sematics are that much different at the start and end.

Hi,

Sorry for the confusion. You are right. We dont need the transaction attribute related code for BMT's. Now I commented out that code.

I tried to close the session before commiting as you advised. In that case also, I got the same exception. I've also checked for the correct jta.UserTransaction property in the configuration(Set as "UserTransaction" since I'm using JBoss).

I have a doubt. Irrespective of whether we are using CMT or BMT will the call sessionfactory.openSession() correctly associate the session with the underlying transaction?

ie., if we write code like this...



Will the above code work?

To make sure that the EJB code is working properly, I manually gave a connection(got separately) while opening the session and used the session transaction for controlling the code and it worked perfectly.



Can you please explain me how to use UserTransaction with Hibernate?

Regards,
Balakrishnan.

You need to make certain that the datasource that Hibernate is obtaining connections from is a JTA datasource.

Sorry for this dumb question. How do I verify this? Currently I've configured the JBoss connection pool to use with the hibernate.

To add on this, I've changed the connection pool from JBoss to DBCP connection pool. Now I'm not getting the error. But now the entries are not updated to the database. Also no error is shown by hibernate.

Here's the code I'm using.




Also, I've changed the UserTransaction to something like this...



Here also I'm not getting any errors but no changes are updated to DB.

Can anybody please help me how to proceed on this.

Regards,
Balakrishnan.

Be sure to flush the session prior to committing transactions. I did not see that call in your code snippets.

Be sure to flush the session prior to committing transactions. I did not see that call in your code snippets.


If he is using Hibernate Transactions, flush() is called from Transaction.commit(). You don't need to do it manually.

Even after calling the flush() before the session is closed, the changes are not updated to the database.

Now, I have a doubt. Can you please explain me how hibernate attaches the session to JBoss's transaction in case of BMTs? From the problems I've been facing, it looks like the hibernate session is not correctly associated with the jboss BMT user transaction. Is there any configuration that needs to be made explicity for enabling Hibernate to attach to the Jboss BMT user transactions? Do I need to set the parameter "jta.UserTransaction" for enabling this? (Currently I've set the parameter to "UserTransaction")

I really don't know what you mean by "associating a session with the transaction".


The session doesn't get associated with a transaction. That is the job of the JDBC connection pool.

Assume the case with the following BMT code



What I infer from what you say is that the hibernate session gets access to the DB connection from the JBoss when I say sessions.openSession().
And in the call session.flush(), it writes to the DB from the in-memory representation using the connection, it got. So, in the above case, when I say ut.commit(), my work should have been committed to the DB.

But, my problem is that its not being committed. :-(
I just want a way to make sure that Hibernate gets the DB connection from JBoss (when I call openSession()). Any help of debugging??

PS: I assume that JBoss connection pools is JTA enabled (as all my BMT code were working fine!)

OK, in the case of the code you just gave, there is NO WAY that the problem can be Hibernate-related.

It must be a problem with your datasource configuration.

You can easily verify that Hibernate executes the SQL calls when session.flush() is called (just enable logging). Then after that it is no longer Hibernate's responsibility to see the the JDBC connection gets committed!

I think I got the problem!

When I just added a print statement after I got the session, everthing started to work fine.

System.out.println("Got the connection to the database : " + (session.connection() != null));

I think in the session.connection() method, if connection is null, it is fetched.

Do I need to initialize something for the connection to be fetched automatically?

The connection() is fetched an initialized when it is first used. Are you ABSOLUTELY certain this really happened?

Exactly what is the code between openSession() and session.flush()?

This is the code I have:





In the above code, if I comment out the println statement, it is not working.