The xerces jars are present in the lib/endorsed folder of JBoss. These will be picked up by JBoss when its booting. The current version of xerces that is being shipped with JBoss is XercesJ-2.7.1. Does it work when you add a xercesImpl.jar (appropriate version) in your application's WEB-INF/lib folder? At this point, i am just guessing the possible reasons for the ClasscastException and am not yet sure what is causing this. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4093425#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...