The problem is the the Mapping construction is default. Your annotation class is probably not in the lib directory and are loaded by different class loader. So even though the invoking class is in the same package, the a class in the annotation jar cannot call the default constructor loaded by another class loader. Try to move your hibernate annotation jar to the lib directory. TS View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3981626#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...