Sorry to confuse you. I should say "After I startup my JBoss,.." ClassA is invoked by a JSP in app.war rather than JBoss. Thanks for your useful links first. As I mentioned before, I've read all these before this post. To my understanding, do you suggest the following config ? <attribute name="Java2ClassLoadingCompliance">true</attribute> | <attribute name="UseJBossWebLoader">false</attribute> As I am back home, I will try this tomorrow. Thanks for your help again ! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3957707#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...