EJB3 is it possible to mix BMT and CMT?

[Debopam Poddar]

Hi,

Is it possible to mix BMT and CMT as in the next example. TestAddCommand method is under BMT and calls methods of AddCommand and RemoveCommand which is under CMT. Is this possible?

@Stateless(mappedName = "AddCommand",name="AddCommand")
@TransactionManagement(TransactionManagementType.CONTAINER)
public class AddCommand extends TransactionalCommand implements AddCommandLocal{
	private static Logger logger = Logger.getLogger(AddCommand.class.getName());

	@Override
	@TransactionAttribute(TransactionAttributeType.REQUIRED)
	protected Object command(Object[] args) throws Exception {
		if(logger.isDebugEnabled())
			logger.debug("Inserting Object :"+args[0]);
		getEm().persist(args[0]);
		return args[0];
	}
}



@Stateless(mappedName = "RemoveCommand",name = "RemoveCommand")
@TransactionManagement(TransactionManagementType.CONTAINER)
public class RemoveCommand extends TransactionalCommand implements RemoveCommandLocal {
	private static Logger logger = Logger.getLogger(RemoveCommand.class.getName());

	@Override
	@TransactionAttribute(TransactionAttributeType.REQUIRED)
	protected Object command(Object[] args) throws Exception {
		if(logger.isDebugEnabled())
			logger.debug("Removing :"+args[0]);
		getEm().remove(args[0]);
		return null;
	}
}

=========================================================
@Stateless(mappedName = "TestAddCommand",name="TestAddCommand")
@TransactionManagement(TransactionManagementType.BEAN)
public class TestAddCommand extends TransactionalCommand implements AddCommandLocal{
	@EJB AddCommandLocal addcommand;
	@EJB RemoveCommandLocal removeCommand;
	@Resource private EJBContext context;
	
	private static Logger logger = Logger.getLogger(TestAddCommand.class.getName());

	@Override
	@TransactionAttribute(TransactionAttributeType.REQUIRED)
	protected Object command(Object[] args) throws Exception {
		UserTransaction tx = context.getUserTransaction();
		tx.begin();
		try{
		addcommand.execute(null, (Object[])args[0], null);
		removeCommand.execute(null, (Object[])args[1], null);
		tx.commit();
		}catch(Exception e){
			tx.rollback();
		}
		
		return args[0];
	}
}

[H Paul]

1. Is workable advisable?? (and why not?)

2. For experiment sake,

2.1 For RemoveCommand, instead of return null;
just throw new Exception();

2.2 Run TestAddCommand to see if you have a total rollback and especially for AddCommand in this experiment.

[Piotr Nowicki]

Yes, it is possible to mix BMT and CMT. Moreover - the JTA started by the BMT can be reused by CMT, but not the other way around.
So if you have:

Client -> BMT -> CMT(REQUIRED), the CMT will reuse the transaction started by the BMT.
Client -> CMT -> BMT, the BMT will not be able to reuse the transaction started by the BMT.

HTH.

Cheers!

PS. This might be useful for you: http://stackoverflow.com/questions/7196242/why-does-cmt-commit-on-exit-of-ejb-method-when-transaction-attribute-is-required/7218283