CODEWITHSUNDEEP
javahibernatejpaormpersistence
ServerSideCat
ServerSideCat

Reputation: 2062

Inheritance between entities within one table

I know the question can be simple, but, anyhow, I want to implement simple parent-child relations in one table using hibernate:

Parent
|       \
Child1  Child2
|           |
Junior1    Junior2

so it should looks like the following in the database:

id |  name | parent_id
1    Parent   null
2    Child1    1
3    Child2    1
4    Junior1   2
5    Junior2   3

In case of @Entity class:

@Entity
@Table(name = "PARENT_CHILD")
public class ParentChild {

    @Id
    @Column(name = "ID", nullable = false, unique = true)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    @Column(name = "NAME", nullable = false)
    private String name;

    private String parentId; // <------ how this should be mapped?
}

What is the best practice on how i should map the parentId or make the following another way? Thank you

Upvotes: 0

Views: 38

Answers (1)

L&#234; Thọ
L&#234; Thọ

Reputation: 414

Normally, you can create a relational mapping to map within StateEntity

@ManyToOne
@JoinColumn(name="parent_id", referencedColumnName="id")
private ParentChild parent;

in case it is a parent, then its parent can be null.

If in your project, due to performance there is case you want to load parent_id only instead of the whole ParchentChild parent instance. You can add column mapping as well

@Column(name="parent_id", insertable=false, updatable=false)
private int parentId;

insertable=false, updatable=false is too make sure your system can update parent_id through @ManyToOne field only

Upvotes: 1

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