 or rollback</b>: If the <tt>close</tt> method is called on the <tt>MessageProducer</tt> or its
 <tt>Session</tt> or <tt>Connection</tt> then the Jakarta Messaging provider must block until any incomplete send operations have
 been completed and all <code>CompletionListener</code> callbacks have returned before closing the object and returning. If
 the session is transacted (uses a local transaction) then when the <tt>Session</tt>'s <tt>commit</tt> or
 <tt>rollback</tt> method is called the Jakarta Messagin