Hi, I have already tried this in user forum, but I got no answer. I'm getting java.lang.ClassFormatError: Illegal class modifiers in class test/app1/EmployeeImpl: 0x431. This exception is thrown when using custom ClassLoader and calling defineClass method. I don't change the modifiers of the class in any way, but the rest of the class may be altered. Is this a known problem, or am I doing something wrong? Thanks for help. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3992416#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...