Issues with TimerListener in a SIPServlet

Question

I am developing a SipServlet that runs on the Oracle OCCAS platform. I need to implement a timer such that when it is fired (ie expired), a specific set of actions are taken. Looking at the SIPServlet 2.0 API, it appears that TimerService and TimerListener implemented in the API would do the trick. The servlet does implement the TimerListener interface, the sip annotation @SipListener is used and the timeout method is overridden in the servlet class. In the servlet class, we handle Invite messages using the doInvite protected method. The behavior seen is that the timeout method will not be executed until all the processing in the doInvite method is performed. The processing we want is when the timer expire, the processing in the doInvite method stops and the timeout method takes over. Is this normal behavior or I have missed something?