Hibernate foreign key as part of primary key

Question

I have to work with hibernate and not very sure how solve this problem, I've 2 table with a 1..n relationship like this:

-------
TABLE_A
-------
first_id (pk)
second_id (pk)
[other fields]

-------
TABLE_B
-------
first_id (pk)(fk TABLE_A.first_id)
second_id (pk)(fk TABLE_A.second_id)
third_id (pk)
[other fields]

How can I manage this with Hibernate???

I don't have idea how to manage the primary key for the second table...

Answer 1

There is an example which is completely similar to your case in the Hibernate reference documentation. Just before this example, you'll find the explanations. Here's the example, which matches your problem (User is table A, and Customer is table B):

@Entity
class Customer {
   @EmbeddedId CustomerId id;
   boolean preferredCustomer;

   @MapsId("userId")
   @JoinColumns({
      @JoinColumn(name="userfirstname_fk", referencedColumnName="firstName"),
      @JoinColumn(name="userlastname_fk", referencedColumnName="lastName")
   })
   @OneToOne User user;
}

@Embeddable
class CustomerId implements Serializable {
   UserId userId;
   String customerNumber;

   //implements equals and hashCode
}

@Entity 
class User {
   @EmbeddedId UserId id;
   Integer age;
}

@Embeddable
class UserId implements Serializable {
   String firstName;
   String lastName;

   //implements equals and hashCode
}

Note: it would be much much simpler of you had a surrogate identifier for those two tables. Unless you're forced to deal with a legacy schema, do yourself a favor and use surrogate keys.