I have created this JIRA issue
http://java.net/jira/browse/JMS_SPEC-49
This issue was raised by Graham. As always, please do give your comments.
Improve specification of ExceptionListener
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The use of a ExceptionListener is described in the JMS 1.1 specification in section 4.3.8 "ExceptionListener":
"If a JMS provider detects a problem with a connection, it will inform the connection's ExceptionListener, if one has
been registered. To retrieve an ExceptionListener, the JMS provider calls the connection's getExceptionListerer()
method. This method returns the ExceptionListener for the connection. If no ExceptionListener is registered, the value
null is returned. The connection can then use the listener by calling the listener 's onException() method, passing it a
JMSException describing the problem.
"This allows a client to be asynchronously notified of a problem. Some connections only consume messages, so they would
have no other way to learn their connection has failed.
"A Connection serializes execution of its ExceptionListener.
"A JMS provider should attempt to resolve connection problems itself prior to notifying the client of them.
"The exceptions delivered to ExceptionListener are those that have no other place to be reported. If an exception is
thrown on a JMS call it, by definition, must not be delivered to an ExceptionListener (in other words, ExceptionListener
is not for the purpose of monitoring all exceptions thrown by a connection)."
Despite this, there have been a number of questions about the use of an ExceptionListener. These questions are listed
below, together with proposed answers. It is proposed that the answers to these questions be incorporated into the
specification.
***Question 1:* When Connection.stop() or Connection.close() is called, must these methods wait until any active calls
to ExceptionListeners for that connection have returned, in the same way that they must wait until any active call to
MessageListeners have returned?
***Proposed answer:* No.
***Question 2:* Is there any restriction on the use of Connection.stop() or Connection.close() from an ExceptionListener?
***Proposed answer:* No.
***Question 3:* What does "a Connection serializes execution of its ExceptionListener" mean?
***Proposed answer:* This means that if a connection encounters multiple problems and therefore needs to call its
ExceptionListener multiple times, then it will only invoke onMessage() from one thread at a time. Note however that if
the same ExceptionListener is registered with different connections then it is undefined whether these connections could
call onMessage() from different threads simultaneously.
***Question 4:* What is the effect of ExceptionListener.onException() being slow or blocking?
***Proposed answer:* This is undefined. There is no requirement that any other operation need block until
ExceptionListener.onException() has return, apart from other calls to ExceptionListener.onException() for the same
connection.