I should probably clarify, the exception gets thrown the first time, but the second update appeared to succeed when in fact it silently dropped. I've done quite a bit of rearranging now, and haven't reproduced the problem. As for checking the unique constraint by hand before possibly violating it, I suppose I can live with that, even if it violates DRY. The how of that however is still a bit elusive -- checking it in the action method seems to come too late, because the model values have already been updated, and I get dumped into the debug page due to constraint violations while accessing other components -- namely a datamodel that lists related entities, one of which might actually have the conflicting name. I tried using a separate entityManager so I wouldn't be reading the current transaction's dirty data, but that didn't pan out either -- the datamodel just ended up null. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3982466#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...