Acknowledgements
I first want to thank everyone for all the great work and selfless contributions of the Hibernate team and all those who contribute to the project through patches or helping people in this forum or through other means. I also appreciate the generous support of JBoss and therefore RedHat in making this project possible.

My Failures
I did not find "unsigned" in the index of Hibernate In Action.

I did not find "unsigned" in the API docs for org.hibernate.mapping.Column

I did not find anything in the online docs or the faq.

Google said: Your search - unsigned site:www.hibernate.org - did not match any documents.

I found a couple of other posts in these forums asking the same question but not getting an answer:

http://forum.hibernate.org/viewtopic.php?p=2315074
http://forum.hibernate.org/viewtopic.php?p=2386439

The Problem
The last of these posts suggests that Hibernate does not support unsigned data types (e.g. unsigned byte). Can someone please confirm that for me?

I cannot remember that Java directly supports "unsigned"; all int types are signed.
So, if you need to have this, you will have to create a user type.

Doh! So it's Java that doesn't support unsigned types. That makes a lot of sense. Thank you!