Question

I’ve got three tables in my database:

create table A (
  a_id int primary key
);

create table B (
  b_id int primary key references A(a_id)
);

create table C (
  c_id int primary key,
  b_id int references B(b_id)
);

and I modelled them using following JPA-annotated classes:

@Entity(name = "A")
@Table(name = "A")
public class A {
    @SuppressWarnings("unused")
    @Id
    @Column(name = "A_ID")
    private int id;
}

@Entity(name = "B")
@Table(name = "B")
@PrimaryKeyJoinColumns({@PrimaryKeyJoinColumn(name = "B_ID", referencedColumnName = "A_ID")})
public class B extends A {
}

@Entity(name = "C")
@Table(name = "C")
public class C {
    @SuppressWarnings("unused")
    @Id
    @Column(name = "C_ID")
    private int id;

    @SuppressWarnings("unused")
    @OneToOne(cascade = {CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH, CascadeType.DETACH})
    @JoinColumns(value = {
        @JoinColumn(name = "B_ID", referencedColumnName = "B_ID", insertable = false, updatable = false)})
    private B b;
}

When I try to use these classes with Hibernate entity manager, it complains with the following error:

Unable to find column with logical name: B_ID in org.hibernate.mapping.Table(A) and its related supertables and secondary tables

Changing referencedColumnName ont the C to B join to A_ID seems to make it happy. Why is that? Can’t I model the relationships as they are in the database?

Answer 1

What was missing was a specification of inheritance strategy:

@Entity(name = "A")
@Table(name = "A")
@Inheritance(strategy = InheritanceType.JOINED)
public class A {
    @SuppressWarnings("unused")
    @Id
    @Column(name = "A_ID")
    private int id;
}

The JPA default is SINGLE_TABLE, which collapses entire class hierarchy into a single table.