CODEWITHSUNDEEP
javahibernatejpapersistence
Vojtěch
Vojtěch

Reputation: 12416

Persisting @OneToMany relations with @JoinColumn and @MapKeyColumn

I have two entities:

@Entity
Article {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @OneToMany(fetch = FetchType.EAGER, cascade=CascadeType.ALL)
    @JoinColumn(name="embed_id", referencedColumnName="id")
    @MapKeyColumn(name = "language")
    @MapKeyEnumerated(EnumType.ORDINAL)
    private Map<Language, Locale> locales;

    Article() {
        locales.put(Language.CS, new Locale());
        locales.put(Language.EN, new Locale());
    }
}

@Entity
Locale {
    @Id
    private Long embed_id;

    @Id
    private Language language;

    @Column(length = 256)
    private String name;
}

Thanks to the constructor, I can make sure, that once an Article is instantiated, two Locales (with CascadeType.ALL) are associated with it.

The problem comes when I try to persist such entity - I am getting:

javax.persistence.EntityExistsException: 
a different object with the same identifier value was already associated 
      with the session: org...Locale#org...Locale@2bfdsc64

The problem is that neither embed_id, nor language have assigned values from the Article when persisting and Hibernate does not associate them after persisting Article. How can this be done?

Edit 1:

I checked that when the embed_id and language are set manually, everything works correctly. I just need to tell Hibernate, to set the value of @JoinColumn and @MapKeyColumn according to the @OneToMany relation.

Edit 2:

The problem with MapKeyColumn has an easy solution:

 public void addLocale(Language l, Locale locale) {
      locale.setLanguage(l);
      this.locales.put(l);
 }

But I am still unable to tell hibernate to associate the Locale.embed_id from Article.id.

Edit 3:

I can see that the ID of article is properly generated, but then it is not put in the locale:

DEBUG org.hibernate.event.internal.AbstractSaveEventListener - 
    Generated identifier: 87, using strategy: org.hibernate.id.SequenceGenerator
DEBUG org.hibernate.event.internal.AbstractSaveEventListener - 
    Generated identifier: component[language,embedId]{language=0, embedId=null}, using strategy: org.hibernate.id.CompositeNestedGeneratedValueGenerator
DEBUG org.hibernate.event.internal.AbstractSaveEventListener - 
    Generated identifier: component[language,embedId]{language=1, embedId=null}, using strategy: org.hibernate.id.CompositeNestedGeneratedValueGenerator

Upvotes: 4

Views: 2838

Answers (2)

Vojtěch
Vojtěch

Reputation: 12416

I finally found the anwswer! The trick was to create Setter on Article and add Access to id as follows:

@Id
@Getter
@Access(AccessType.PROPERTY)
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

public void setId(Long id) {
    this.id = id;
    this.getLocale(Language.CS).setEmbedId(id);
    this.getLocale(Language.EN).setEmbedId(id);
}

Upvotes: 0

Johannes Egger
Johannes Egger

Reputation: 4031

I guess the problem is, that you want to persist two empty locales. And because you don't use a generator for the id-fields, the locales have the same (empty) primary key and therefore can't be persisted.

Upvotes: 3

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