问题
I know about container managed transactions(CMT). I also know about the different possible values of the enumerated type TransactionAttributeType. Since the client never calls a MDB directly, the attribute types other than the REQUIRED and NOT_SUPPORTED do not make sense for MDB's as there is no client initiated transaction to join to. So when should I annotate the onMessage() method of an MDB with REQUIRED vs NOT_SUPPORTED? What will be the default behavior in none of the two options is mentioned?
回答1:
What will be the default behavior in none of the two options is mentioned?
The default behavior for Container-managed MDBs is NOT_SUPPORTED.
So when should I annotate the onMessage() method of an MDB with REQUIRED vs NOT_SUPPORTED?
Using NOT_SUPPORTED means - if a failure occurs in onMessage() - any updates/operations that occurred prior to the failure will not be rolled back; this is undesirable for atomic operations involving disparate resources.
If you don't want that behavior, use REQUIRED, put a try/catch in onMessage(), and call setRollbackOnly() in catch() when any exceptions occur. You will need XA drivers if onMessage() is performing multiple operations across different resources; for instance, updating a database and sending a new JMS message in the same transaction will most certainly require XA compatible drivers.
MDB's support only REQUIRED or NOT_SUPPORTED
MDB's may use REQUIRED or NOT_SUPPORTED transaction attributes; other attributes don't make sense since they require client context.
The container always starts a new transaction before calling onMessage(). If another method is called from onMessage(), the container passes along the current transaction context.
回答2:
I'm interested at this discussion. I was convinced that specs indicates that default transaction attribute is REQUIRED.
Some guys in another stackoverflow discussion :
What is the default TRANSACTION ATTRIBUTE for MDBS?
spoke about exception on Weblogic server implementation.
来源：https://stackoverflow.com/questions/24120389/when-should-i-use-required-vs-not-supported-as-a-the-value-of-transactionat