Hibernate 3.1.3
Annotations 3.1 Beta 9

I am trying to update an object with a custom where clause so that proper optimistic locking can be done. Is that possible?

I could not find anything in the session API to allow me to update an object and at the same time specifying a custom where clause.

Also, on a related object, how do I update an object and only update certain columns?

You can't use save or update or any of the other Session-provided save methods with a custom where clause. But my answer to your "On a related object" question will help...

The new HQL parser has support for an "update" keyword, so you can write a special query to update a few columns. If you want certain columns to be read-only always, you can add update="false" in their mapping.
If HQL doesn't support whatever your optimistic locking keywords are, you can use raw SQL to do it, via an SQL query. You probably don't want to use the sql-upadte element in your mapping file, as that's always used to save, whereas a custom update query can be used when you need optimistic locking, and ignore when you don't need it.

The custom query stuff looks cool, but I plan to play with Annotations, so no mapping files for me. Is there an annotated way to specify a custom query for save and updates for Annotations?

Thanks!

I know nothing about annotations, but you can certainly create unnamed queries in the normal way (Session.createQuery()). I presume that named queries can be specified in annotations, but I don't know how.