WebLogic Message Unit-of-Order explanation
Example for UOE(Unit Of Order) Somebody enter in a web application (store) for buying a book and choose a book (M1= message number 1). After that, that person immediately cancel that action (M2= message number 2). In this case the following things may happen: 1) MDB 1(Message Driven Beans 1) read the first message (M1) and start processing that message. 2) MDB2 (Message Driven Beans 2) read the second message (M2) and start processing that message. 3) For some reasons (MDB2 run faster than MDB1), MDB2 try to cancel that operation by sending a "DELETE" operation to the database, but nothing happen, because MDB1 didn't "INSERT" that operation to the database. 4) MDB1 "INSERT" that operation to the database. At the end the book appears in the database as "INSERTED", so that book will be sent to the person who wanted it at the beginning (but is no longer needed). In order to avoid this problem, WebLogic in...