What does a Hibernate join table class using composite keys and @NaturalId look like?

Question

I found this before:

http://stackoverflow.com/questions/1212058/how-to-make-a-composite-primary-key-java-persistence-annotation

There's a code snippet on the first answer:

@Entity
public class UserRole {
  @Id
  @GeneratedValue
  private long id;

  @NaturalId
  private User user;
  @NaturalId
  private Role role;
}

So, not using artificial dummy IDs, how would the class look like?

@Entity
public class UserRole {

  @?
  @NaturalId
  private User user;

  @?
  @NaturalId
  private Role role;
}

Do I need an inner "ID class" nontheless? Can I use @IdClass on the two references instead (where marked "@?")?

I'd really find it more natural to override equals and hashCode in this class instead of the "ID class", so such a design would be a lot better. Can you produce something like the above and if so, which annotations do you need?

Karsten