About setRollbackOnly method in a transaction

[Himai Minh]

On p.177 of EJB in Action,

The setRollbackOnly mehtod on the EJBContext can only be used in methods that have a transaction attribute type of REQUIRE, REQUIRED_NEW or MANDATORY. If a transactions hasn't been started, as in the case of SUPPORTED or NEVER, a java.lang.IllegalStateException will be thrown.

What about this case ?
A method is annotated with a transaction attribute type of SUPPORT. And this method will join an existing transaction. Can we roll back changes in this method ? I assume we cannot roll back changes in such a method, based on this quote. Then, is it possible to roll back any changes?

[E Armitage]

The specs say

Only enterprise beans that will execute correctly in both modes should use the SUPPORTS transaction attribute.

You can't guarantee that the method will be called with a transaction present so you wouldn't know when to do the rollback and when not to. If a transaction exists it will probably work because the specs only say the exception is thrown if "the instance is not allowed to use this method (i.e. the instance is of a bean with bean-managed transactions)." but it will be very bad practice to use transaction semantics in a method marked as SUPPORTS.

[Himai Minh]

Thanks for your reply.
So, using the placeOrder() method in the EJB in Action as an example:

 //Psuedo code
@Inject
EJBContext context;
@TransactionManagement(TransactionAttributeType=SUPPORT)
public void placeOrder(){

          try{
                     bid.chargeCreditCard();
               }
         catch(CreditCardProcessingException e){
                 context.setRollback();      //This won't guarantee to roll back and it will throw the illegalStateException ?
            }
}

[E Armitage]

Whether it will throw an exception or not could be implementation specific. The API specs don't explicitly say what will happen. The code is a contradiction. It declares that the method doesn't care about the presence of a transaction and yet it goes on to try and use it.