OK, let's burn some of my so precious credits...

I've just read the page about managing Enum data, on page http://www.hibernate.org/272.html.

While looking at the "flexible solution" proposed, I've noticed that AbstractUserType abstract class, extended by GenericEnumUserType.

And here is my question : what is this AbstractUserType that eclipse can't find anywhere in my jars...

Thank you

There isn't one. Presumably it's just a default implementation that the author uses so he doesn't have to re-implement every method, every time. Don't extend it, implement every method in your class, it should be fine.