When a bean calls createTimer( ), the operation is performed in the scope of the current transaction. If the transaction rolls back, the timer is undone: it’s not created (or, more precisely, uncreated). For example, if the Ship EJB’s scheduleMaintenance( ) method has a transaction attribute of RequiresNew, a new transaction will be created when the method is called. If an exception is thrown by the method, the transaction rolls back and the new timer event is not created.

In most cases, the ejbTimeout( ) method on beans should have a transaction attribute of RequiresNew. This ensures that the work performed by the ejbTimeout( ) method is in the scope of container-initiated transactions. Transactions are covered in more detail in Chapter 16.