I've upgraded to Hibernate 3.6.10 and Hibernate.custom has been removed, what replaced it?

I'm using an inhouse-written Hibernate custom UserType with query.addScalar calls.

That's a very old Hibernate version that we no longer support.

I don't think there's any substitute for that. In fact, there is a good chance that UserType is going to be removed completely in Hibernate 6, so that you need to use generic Types instead.

Check out this article for how you can use SqlTypeDescriptor and JavaTypeDescriptor to build a custom Type. The article was written for Hibernate 5, so you'll have to adapt it for 3.6 accordingly.

If you're stuck on 3.6 then you want org.hibernate.usertype.UserType now. Although I agree with vlad that it would be better if you can upgrade and use newer solutions.