CODEWITHSUNDEEP
javahibernatejpa
N2O
N2O

Reputation: 33

Hibernate and JPA: how to make a foreign key constraint on a String

I am using Hibernate and JPA. If I have two simple entities:

@Entity
@Table(name = "container")
public class Container {
  @Id
  @Column(name="guid")
  private String guid;
}

@Entity
@Table(name="item")
public class Item {
  @Id
  @Column(name="guid")
  private String guid;

  @Column(name="container_guid")
  private String containerGuid;
}

and I want to insure that inserting an Item fails if the referenced Container does not exist. I would prefer not to have a Container object populated inside the item object (ManyToOne), how would I do this if it is possible to do?

Upvotes: 3

Views: 3541

Answers (2)

axtavt
axtavt

Reputation: 242786

You can declare arbitrary constraint using columnDefinition attribute:

@Column(name="container_guid", 
     columnDefinition = "VARCHAR(255) REFERENCES container(guid)")
private String containerGuid;

Note, however, that Hibernate doesn't know anything about this constraint, so that, for example, it may not perform inserts in proper order with respect of it and so on.

Therefore it would be better to create a @ManyToOne relationship. If you are afraid of extra SQL query for Container needed to set this property, you can use Session.load()/EntityManager.getReference() to get a proxy without issuing actulal query.

Upvotes: 6

VolatilitySmile
VolatilitySmile

Reputation: 11

Try using below relationship mapping

RelationShip Mapping @OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@ManyToOne() @ManyToMany()

<> @JoinColumn(name="<>")

Upvotes: -3

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