Foreign key constraint error in JPA

Question

I have three entities which look like this:

@Entity
class EntityA{       
    @OneToMany(cascade = javax.persistence.CascadeType.ALL, orphanRemoval = true)
    private List<EntityB> _candidates = null;
}

@Entity
class EntityB{       
   @OneToOne
   private EntityC _comp;
}

@Entity
class EntityC{
...
}

EntityB has a property of type EntityC. When an instance instanceC of EntityC is deleted, all the instances instancesB of EntityB referencing it must be deleted as well, from the instances of EntityA containing the instancesB.

Can I achieve this behavior through annotations? In the current state of the code, when deleting an EntityC object I get the following exception:

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails

Answer 1

Your B table has foreign keys to both A and C with your current mappings which must be maintained. Because the fk to A is controlled by A's OneToMany to B, this one wont be too much of a problem as long as you remove A's reference to B when you delete B, just to keep your cached entities in sync the the changes. The relation to C on the other hand requires you to dereference C from B before it can be deleted, that or delete B as well- otherwise the fk in the B table will remain, violating the constraint. As the comments state, you will need some level of relationship management when removing entities.