The setListening(boolean) in Session method doesn't stop the listening thread immediatly, and doesn't prevent the listening thread from starting. Today, invoking setListening(false) will allow the listening thread to consume one message before it disables listening.

A quick fix is to not start the listening thread if the message listener is null.

This bug is pretty sever since it is not possible to use readMessage() in Session to perform a "blocked" reading since the first message is always consumed by the listener.