In the one-to-one association using a primary key association example on page 223 of "Hibernate In Action", the one between user and address, how do I get the address to be deleted?

Let's say I create a user, give it an address and call save. Hibernate inserts the user into the user table and the address into the address table. Now, let's say the user becomes homeless. How do I get the address to be deleted? If I do user.setAddress(null), Hibernate does nothing. How do I get Hibernate to recognize that the other-end of the association, the address, is gone and must be deleted?

session.delete() or enable cascading.

I have enabled cascading. I have cascade="all" in the mapping (the DTD does not like cascade="all-delete-orphan" for a one-to-one mapping).

Here's what I am doing:

...get session
User u = new User();
u.setUid(123);
Address a = new Address();
a.setUid(123); // not really needed
a.setUser(u);
u.setAddress(a);

session.save(u);
tx.commit(); // Hibernate inserts user and address

u.setAddress(null);

session.save(u);
tx.commit(); // Hibernate does nothing! I expect it to delete address.

Do I explicitly need to call session.delete(a) to delete the address? I should be able to use one-to-one associations as shown above and expect Hibernate to delete the other end of the association, shouldn't I?