Hibernate JPA @PrimaryKeyJoinColumn Example

@PrimaryKeyJoinColumn

The @PrimaryKeyJoinColumn annotation is used to specify that the primary key column of the currently annotated entity is also a foreign key to some other entity (e.g. a base class table in a JOINED inheritance strategy, the primary table in a secondary table mapping, or the parent table in a @OneToOne relationship).


PrimaryKeyJoinColumn Specifies a primary key column that is used as a foreign key to join to another table.
It is used to join the primary table of an entity subclass in the JOINED mapping strategy to the primary table of its superclass; it is used within a SecondaryTable annotation to join a secondary table to a primary table; and it may be used in a OneToOne mapping in which the primary key of the referencing entity is used as a foreign key to the referenced entity.

If no PrimaryKeyJoinColumn annotation is specified for a subclass in the JOINED mapping strategy, the foreign key columns are assumed to have the same names as the primary key columns of the primary table of the superclass.


    Example: Customer and ValuedCustomer subclass

    @Entity
    @Table(name="CUST")
    @Inheritance(strategy=JOINED)
    @DiscriminatorValue("CUST")
    public class Customer { ... }
   
    @Entity
    @Table(name="VCUST")
    @DiscriminatorValue("VCUST")
    @PrimaryKeyJoinColumn(name="CUST_ID")
    public class ValuedCustomer extends Customer { ... }

 Derived identifier @PrimaryKeyJoinColumn

@Entity(name = "Person")
public static class Person  {

@Id
private Long id;

@NaturalId
private String registrationNumber;

public Person() {}

public Person(String registrationNumber) {
this.registrationNumber = registrationNumber;
}

//Getters and setters are omitted for brevity
}

@Entity(name = "PersonDetails")
public static class PersonDetails  {

@Id
private Long id;

private String nickName;

@OneToOne
@PrimaryKeyJoinColumn
private Person person;

public void setPerson(Person person) {
this.person = person;
this.id = person.getId();
}

//Other getters and setters are omitted for brevity
}