What os durable subscriber

With a durable subscriber, the subscriber can be closed and recreated, but the subscription continues to exist and to hold messages until the application calls the unsubscribe method. In Figure  create stands for a call to TopicSession.createDurableSubscriber, close stands for a call to TopicSubscriber.close, and unsubscribe stands for a call to TopicSession.unsubscribe. Messages published while the subscriber is closed are received when the subscriber is created again. So even though messages M2, M4, and M5 arrive while the subscriber is closed, they are not lost.