Your WEB-INF/lib contains many jars which already are present in the server/< serverName>/lib folder of JBoss. If you want to retain them, then you can go for classloader isolation for your application as explained in these wiki articles: http://wiki.jboss.org/wiki/Wiki.jsp?page=ClassLoadingConfiguration http://wiki.jboss.org/wiki/Wiki.jsp?page=JBossClassLoadingUseCases http://wiki.jboss.org/wiki/Wiki.jsp?page=ClassLoadingOverview The other option is to remove the jars which are causing problem, from your application's lib folder. I guess, for this specific exception you might have to remove (or go for classloader isolation) the following jars from WEB-INF/lib folder: anonymous wrote : jasper-compiler.jar | jasper-compiler-jdt.jar View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4111103#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...