I am trying to map a normalized Java model to a legacy database schema using Hibernate 3.5. One particular table encodes a foreign keys in a one-to-many relationship as a bit array column.

Consider tables 'person' and 'clubs' that describes people's affiliations to clubs:

person  .----.------.    club: .----.---------.---------------------------.
        | id | name |          | id |   name  | members | binary(members) |
        |----+------|          |----+---------|---------+-----------------|
        |  1 | Bob  |          | 10 | Cricket |       0 |             000 |
        |  2 | Joe  |          | 11 | Tennis  |       5 |             101 | 
        |  3 | Sue  |          | 12 | Cooking |       7 |             111 |   
        '----'------'          | 13 | Golf    |       3 |             100 |
                               '----'---------'---------'-----------------'

So hopefully it is clear that person.id is used as the bit index in the bit array club.members. In this example the members column tells us that:

• no one is a member of Cricket,
• Bob/Sue -> Tennis,
• Bob/Sue/Joe -> Cooking and
• Sue -> Golf.

In my Java domain I'd like to declare this with entities like so:

class Person {
    private int id;
    private String name;
    ...
}

class Club {
    private Set<Person> members;
    private int id;
    private String name;
    ...
}

I am assuming that I must use a UserType implementation but have been unable to find any examples where the items described by the user type are references to entities - not literal field values - or composites thereof. Additionally I am aware that I'll have to consider how the person entities are fetched when a club instance is loaded.

Can anyone tell me how I can tame this legacy schema with Hibernate?