How to inherit @ForeignKey settings when using TABLE_PER_CLASS inheritance strategy

Question

I try to control the foreign key name generation using the @ForeignKey annotation. This usually works well. But in a special case it does not what I want and I don't know how to configure it.

The special case is when I use @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS). When the base class has a @ManyToOne relationship and I want to specify the foreign key name using @ForeignKey it only applies for the base class.

         +------------+           +--------------+
         | BaseEntity |   ----->  | OtherEntity  |
         +------------+           +--------------+
                ^
                |
       +--------+---------+
  +----------+      +----------+
  |SubEntity1|      |SubEntity2|
  +----------+      +----------+

My BaseEntity

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@Table(name = "base_entity")
public class BaseEntity {

    @Id
    @GeneratedValue
    private Long id;

    @ManyToOne
    @JoinColumn(foreignKey = @ForeignKey(name = "FK_other_entity"))
    private OtherEntity otherEntity;
}

My SubEntity1 (same for the the SubEntity2)

@Entity
@Table(name = "sub_entity_1")
public class SubEntity1 extends BaseEntity {
}

and just to be complete .... the OtherEntity:

@Entity
@Table(name = "other_entity")
public class OtherEntity {
    @Id
    @GeneratedValue
    private Long id;
}

Hibernate will generate a ddl script containing the following foreign key definitions:

alter table base_entity 
   add constraint FK_other_entity 
   foreign key (otherEntity_id) 
   references other_entity (id);

alter table sub_entity_1 
   add constraint FK_jtmdc6tiytduxbpesmng9g3bk 
   foreign key (otherEntity_id) 
   references other_entity (id);

alter table sub_entity_2 
   add constraint FK_9xpb6q7qeq5r3pq071cbbiygx 
   foreign key (otherEntity_id) 
   references other_entity (id);

As you can see the sub entities foreign key name is random.

The sub entities don't have a field holding a reference to the OtherEntity, so I can't place a @ForeignKey annotation there.

How can I control the foreign key name for sub entities when using a table per class inheritence type?

I'm using

spring-boot 1.4.3.RELEASE
hibernate 5.6.2.Final

EDIT

I also tried to use @AssociationOverride, but it does not work.

If you need a quick setup for schema generation you might want to take a look at my previous question Generate DDL with spring boot using a custom delimiter

René Link · Answer 1 · 2017-01-28T12:02:09.210

Seems to be a hibernate bug

HHH-10387: In a @AssociationOverride the foreignKey = @ForeignKey is not considered
HHH-11180 JPA @ForeignKey still not consistently applied from annotation binding

I have voted for both bugs. Maybe you want to vote for it too and hopefully it will get fixed soon.

I will observe changes to the issues and update this answer when the bug is fixed.

My "solution for now" is to use InheritanceType.JOINED

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Table(name = "base_entity")
public class BaseEntity {

    @Id
    @GeneratedValue
    private Long id;

    @ManyToOne
    @JoinColumn(foreignKey = @ForeignKey(name = "FK_other_entity"))
    private OtherEntity otherEntity;
}

and set the foreign key of the joined table

@Entity
@Table(name = "sub_entity_1")
@PrimaryKeyJoinColumn(foreignKey = @ForeignKey(name = "FK_base_entity"))
public class SubEntity1 extends BaseEntity {

}

How to inherit @ForeignKey settings when using TABLE_PER_CLASS inheritance strategy

1 Answers1