Transactions (EJB3)

Transactions in EJB3 and Seam

• ACID
• Put all transactions in your EJBs (not in servlets)
  
• Container or Bean Managed (default in Seam)
  
• Container-managed-transactions (CMTs) preferred in Java EE. The Java EE container will handle comitting, rolling back, starting the transaction, etc. (no coding for the transactions).
  
• 6 types of transactions to choose from (default is REQUIRED)
  
• MANDATORY
• REQUIRED
• REQUIRES_NEW
• SUPPORTS
• NOT_SUPPORTED
• NEVER
• Example: Set this annotation before a method to use a transaction independent of an already-active transaction. Will attempt to commit in the end of the method.

  @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
     public void addUser(User user) {
         em.persist(user);
     }

• Bean-managed transactions (BMTs) allows a much more fine-grained control of transactions. (It is recommended to not use BMTs unless you cannot achieve the goals you are looking for using the CMT option.