So, I think I figured out a solution that works for me. In my persistence.xml in my original application EAR, I removed the jar-references and instead added this; | <mapping-file>persistence-mapping-file.xml</mapping-file> | Then, in the persistence.jar within the EAR, I added the persistence-mapping-file.xml containing this; | <?xml version="1.0" encoding="UTF-8" ?> | <entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm" | xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" | xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_1_0.xsd" | version="1.0"> | | <package>myproject.entities</package> | | <entity class="myproject.entities.FooEntity" name="FooEntity" /> | <entity class="myproject.entities.BarEntity" name="BarEntity" /> | | </entity-mappings> | Then I just refer to the same file within the persistence.xmls I deploy in my webapp-EARs and that works more or less as I want. Does seem like a bit non-standard use of the mapping-file from what I could gather from reading some forums and stuff - but hey, it works. And it's good enough. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4019868#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...