Thx. But i view your reference link. the post said "JBoss provides a way to find these duplicate deployments. Go to the JMX console for JMImplementation:service=LoaderRepository?,name=Default http://localhost:8080/jmx-console/HtmlAdaptor?action=inspectMBean&nam... Invoke displayClassInfo with the name of the class ... If you see multiple "Instance1" and multiple CodeSources? then this could be the cause of the ClassCastExceptions that you are seeing. " i cannot see some duplicate deployment. but i see the instance1 it show the following value: Instance1, org.jboss.mx.loading.LoaderRepository, R ,org.jboss.mx.loading.UnifiedLoaderRepository3@166a22b , MBean Attribute. how come View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3981197#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...