"nicdo77" wrote : Well, this leads me to another question. | I already had hibernate2.jar packaged in my ear. BUT, at deployment time, i used to have a deployment failure cause JBoss couldn't find one of the Hibernate class. Where in the ear did you place the hibernate jar file? "nicdo77" wrote : | | Does it seem normal to you to have twice hibernate2.jar? | Nico. Each application is allowed to have its own version of libraries. This means that there might be more than one version of the same jar file in a JBoss system. But you have to be careful about how you setup the classloading configurations. Read through the following links which might give you some idea on classloading in JBoss: http://wiki.jboss.org/wiki/Wiki.jsp?page=JBossClassLoadingUseCases http://wiki.jboss.org/wiki/Wiki.jsp?page=ClassLoadingConfiguration View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4109278#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...