Thanks PeterJ, You were correct ,it's the problem with the class in onMessage method.Here is the code public void onMessage(javax.jms.Message mesg) { try { payGovJMSUtil = PayGovJMSUtil.getInstance(); processMessage(mesg); } catch (Exception e) { e.printStackTrace(); throw new EJBException(e.getMessage()); } return; } But i copied the jar file in which this class(PayGovJMSUtil) exist in server deploy folder along with MDB jar. Looks like its not getting.Please tell me what is the class loader policy and sequence in JBOSS and which is the correct place to put helper jars. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4130564#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...