Sorry, yes, it should EMPTY_SET unless you are going to use jboss retro and convert JBossXB to use java 5. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3977210#3977210 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=3977210