According to section 16.5 in the hibernate 3 reference manual it is possible to write custom load SQL in hbm files. Is this possible somehow when using EJB3/hibernate annotations?

I don't want to resort to using an hbm file to map all the class fields because of one association that requires a special query...

not yet, but a patch is welcome, it should be pretty straightforward

Thanks, but it looks like that would be a bit too much for me.

OK, wrote a patch - but someone beat me to it. It's being tracked in
http://opensource.atlassian.com/projects/hibernate/browse/ANN-37