How to migrate ASP.net Application to Jboss environment.

What procedure should I will follow? Any step-by-step instructions would be very helpful.

That depends entirely on what your ASP.NET app does. Simple apps can be fairly easily ported into servlets and JSPs. More complicated apps will need a lot more work. I recommend that you first draw up the complete architecture of the current app, in a lot of detail (you will need to know the work flow for every request), and then build a Java app to match that architecture.

Needless to say, that is a lot of work. Most companies that I work with won't even bother - they would keep the current ASP.NET app as it is and build new apps using Java EE.