JBoss 4.0.3SP1 seems to be supporting the J2EE Timers very well. However, I would like to know it supports clustering. How I can make sure the same timer instance is installed across JBoss cluster and make sure exactly only one of the instances are used for the onTimeout method called back.?
This is not supported currently. You'd have to use clustered singletons, see the jboss docs.