CODEWITHSUNDEEP
javadatabase-designjpaormannotations
socksocket
socksocket

Reputation: 4371

JPA: foreign key annotation

I've got two database entities: Forum and Topic.

Topic has protected long forumId data member, which indicates of course the Topic's forum.

My question is what annotation to use for this data member?

Upvotes: 42

Views: 145673

Answers (3)

munyengm
munyengm

Reputation: 15489

@ManyToOne As the annotation implies - you have many topics per forum

Upvotes: 1

Yair Zaslavsky
Yair Zaslavsky

Reputation: 4137

As others have answered -
You should use the ManyToOne , and JoinColumn annotations.
Bare in mind , that since JPA is about ORM - Object relational mapping,
You should reference another object as you would have done "naturally" in Java - i.e via an object and not via its identifier (which is forumId) in your case),
This was one of the design consideration between the relations at JPA and Hibernate (previously to JPA).

Upvotes: 6

Elias Dorneles
Elias Dorneles

Reputation: 23916

As Forum has many topics, and a topic belongs to one and only Forum, you probably want to go with a Forum type attribute annotated with @ManyToOne:

@ManyToOne
@JoinColumn(name = "forumId")
private Forum forum;

See more:

ManyToOne and JPA mapping

Upvotes: 55

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