CODEWITHSUNDEEP
javahibernatejpa
robert_difalco
robert_difalco

Reputation: 4914

Person and Child Relationship in JPA where Child is also a Person

In JPA is there any way to model the following kind of relationship?

PERSON
   INT id PKEY
   VARCHAR name

CHILD
   INT parentId FKEY(PERSON->id)
   INT nameId FKEY(PERSON->id)

Where parentId is a many-to-one relationship and nameId is a one-to-one relationship. So, essentially, parentId and nameId would create a compound primary key in CHILD?

Thanks!

Upvotes: 0

Views: 162

Answers (2)

MGPJ
MGPJ

Reputation: 1072

You can create an entity for your scenario. But the table design should be the nameId should be the primary key of the child table and if you have trouble for creating entity class then in NetBeans IDE or Eclipse IDE there is an option for 'Entity class from table' for the entity class creation.

Upvotes: 0

Perception
Perception

Reputation: 80633

I would rename nameId to childId. Logically you have a relationship between a person and its children. Where each child is a person itself. With the model you currently have there is no reason to have a separate child table, but let's assume you will add distinct attributes later on. I would model the relationship using inheritance and aggregation:

@Entity
@Table(name="PERSON")
@Inheritance(strategy=InheritanceType.JOINED)
public class Person implements Serializable {
    @Id
    private Integer id;

    private String name;

    @OneToMany(mappedBy = "parent")
    private List<Child> children;
}

@Entity
@Table(name="CHILD")
@PrimaryKeyJoinColumn(name="nameId", referencedColumnName = "id")
private class Child extends Person implements Serializable {
    @ManyToOne
    @JoinColumn(name = "parentId", referencedColumnName = "id")
    private Person parent;
}

This is sample code, typed verbatim, you will have to error check it yourself. But it's a starting point.

Upvotes: 1

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