In one application scenario, it was required to process the message only once. The message contained a donation amount that needed to be put in the database. Using a Queue and AUTO_ACK semantics, we were able to achieve this. But there was a problem - What would happen if the JMS provider fails before the acknowledgement is received from client. It would send the message again when it comes up. How to avoid this ?
The consumer may receive the message again, because when delivery is guaranteed, it's better to risk delivering a message twice than to risk losing it entirely. A redelivered message will have the JMSRedelivered flag set. A client application can check this flag by calling the getJMSRedelivered() method on the Message object. Only the most recent message received is subject to this ambiguity.