I forgot to add that I'm using JBoss 4.0.3 AS, and MySQL as a database. I have not done anything else to configure it to use MySQL than to add the ds.xml as defined in the tutorial, and ofcourse the internal application mappings. So I don't know if I need to make settings elsewhere to define how it should treat it. But as mentioned, I don't get any errors when I only use my PersonBean which inserts to the person table. (without relations) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3989761#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...