You don't give much detail what you need to find via JMX, we do implement JSR-77 MBeans that includes web deployments, maybe that helps? The spec contains standard naming conventions for the MBeans so that will help you trying to find the MBean that relates to your deployment. Tomcat, depending on the version you use, binds several MBeans to the MBean server as well, depending what you need.
if you go to:
and on the left hand side go to J2EEDomains/Manager/JBoss
you should see all the wars and sars.
For each war you should see a listing of servlets.
Have you tried looking for you application with: