After going through the examples I found that each of the portlet is deployed as separate war file. Now my query is that cant we have the entire application under one war file or is it manadatory that each portlet should lie in different war. If its possible to club the entire appilcation under one file, Give me some sample example if possible.
Yes, you can place multiple portlets into a single war file. For an example, see the jboss-portal.sar/portal-samples.war directory, which contains the news and weather portlets. Notice that the jar file is located at jboss-portal.sar/lib/portal-samples-lib.jar but could just as easily have been located at jboss-portal.sar/portal-samples.war/WEB-INF/libportal-samples-lib.jar.