Java Spring how to use Collection as Foreign Key

Asked Feb 04 '20 at 01:27

Active Feb 04 '20 at 02:05

Viewed 207 times

I hava to entities with One to Many relationship, how to use Set as a foreign key. Country.java

package hello.world.entity;
import javax.persistence.*;

@Entity
@Table(name="country")
public class Country {
    @Id
    @Column(name="code", length=3, nullable=false)
    private String code;

    @Column(name="name", length=256, nullable=false)
    private String name;
}

CountryLanguage.java

@Entity
@Table(name="country_language")
public class CountryLanguage {
    @Id
    private int id; // column Id desnt exist on table

    @ManyToOne(cascade=CascadeType.ALL, targetEntity=Country.class)
    @JoinColumn(name="code")
    private Set<Country> countryCode = new HashSet<>();

    @Column(name="language", length=256, nullable=false)
    private String language;

How can use CountryLanguageRepository to getData by Country code

I have like this right now

@Repository
public interface CountryLanguageRepository extends JpaRepository<CountryLanguage, String> {

    Set<CountryLanguage> findOneByCountryCode(String code);

}

Table CountryLanguage doesnt have an ID, but hibernate ask to add it. I have an Exception

column "id" contains null values

I have a key on table CountryLanguage (code,language)

edited Feb 04 '20 at 02:05

asked Feb 04 '20 at 01:27

DoctorDo

@ScaryWombat why? – DoctorDo Feb 04 '20 at 01:55
Shouldn't one country have many Languages? Oh maybe both is good – Scary Wombat Feb 04 '20 at 01:56
@ScaryWombat aaww sorry, yes one country many languages – DoctorDo Feb 04 '20 at 01:59
well in that case, it is not reversed? – Scary Wombat Feb 04 '20 at 02:00
@ScaryWombat yes, but I have another exception now – DoctorDo Feb 04 '20 at 02:06
I think that Hibernate requires that all entities have a unique ID - see https://stackoverflow.com/questions/4546131/using-unique-constraint-on-hibernate-jpa2/5677533 – Scary Wombat Feb 04 '20 at 02:09
@ScaryWombat can I have primary key on 2 columns as unique keys? – DoctorDo Feb 04 '20 at 02:16
@ScaryWombat I can use EmbeddedId with OneToOne, it will be a key. Right? Will it work like that? – DoctorDo Feb 04 '20 at 02:25

Java Spring how to use Collection as Foreign Key

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