Transaction Demarcation

[Niranjan Deshpande]

@Stateful
@TransactionManagement(BEAN)
public class MySessionBean implements MySession
{
@Resource
private UserTransaction ut;
public void method1(...)
{
// start the transaction
ut.begin();
}
public void method2(...)
{
// commit the transaction
ut.commit();
}
}

Looks weird, but is it valid?

Also, what are the tranaction attributes allowed on timeout methods? and why?

[Promod kumar]

Niranjan,

Yes, it is valid. This is one of the things that you can only do with BMT, start a transaction in one method of a stateful session bean and commit in another method. This is discussed a little bit in EJB3 in action, page 201, section 6.3.4

As for timeout method, Required or Requires_New are allowed (refer to the sidebar EJB Timers and Transactions, page 173 of the same book). I am not sure why only these two are allowed, I am suspecting because the container is invoking the timeout method not a client.

[Treimin Clark]

Promod Mahajan wrote:As for timeout method, Required or Requires_New are allowed.

As I heard, NOT_SUPPORTED is also available, in addition to above two types.

[Niranjan Deshpande]

@Pramod,

Thanks for pointing the relevant pages. The page 201 also says

Another drawback for BMT is the fact that it can never join an existing transaction. Existing transactions are always suspended when calling a BMT method, significantly limiting flexible component reuse.

To avoid this we use joinTransaction( ). Correct?

@Clark,
Yes I have read in Java Beat that NOT_SUPPORTED is also one of the supported types for Time out methods.

[Jun Liu]

To avoid this we use joinTransaction( ). Correct?

No. joinTransaction() is a method of EntityManager. It allows the EntityManager created outside the transcation can join the current transaction. It has nothing to do with the discussion of BMT here.

[Niranjan Deshpande]

Oops! I mixed up thigs terribly!