Cannot use an @IdClass attribute for a @ManyToOne relationship

Question

I have a `Gfh_i18n` entity, with a composite key (`@IdClass`): ``` @Entity @IdClass(es.caib.gesma.petcom.data.entity.id.Gfh_i18n_id.class) public class Gfh_i18n implements Serializable { @Id @Column(length=10, nullable = false) private String localeId = null; @Id <-- This is the attribute causing issues private Gfh gfh = null; .... } ``` And the id class ``` public class Gfh_i18n_id implements Serializable { private String localeId = null; private Gfh gfh = null; ... } ``` As this is written, this works. The issue is that I also have a `Gfh` class which will have a `@OneToMany` relationship to `Gfh_i18n`: ``` @OneToMany(mappedBy="gfh") @MapKey(name="localeId") private Map<String, Gfh_i18n> descriptions = null; ``` Using Eclipse Dali, this gives me the following error: ``` In attribute 'descriptions', the "mapped by" attribute 'gfh' has an invalid mapping type for this relationship. ``` If I just try to do, in `Gfh_1i8n` ``` @Id @ManyToOne private Gfh gfh = null; ``` it solves the prev…

Accepted Answer

You are dealing with a "derived identity" (described in the JPA 2.0 spec, section 2.4.1).

You need to change your ID class so the field corresponding to the "parent" entity field in the "child" entity (in your case `gfh`) has a type that corresponds to either the "parent" entity's single `@Id` field (e.g. `String`) or, if the "parent" entity uses an `IdClass`, the `IdClass` (e.g. `Gfh_id`).

In `Gfh_1i8n`, you should declare `gfh` like this:

```
@Id @ManyToOne
private Gfh gfh = null;
```

Assuming `GFH` has a single `@Id` field of type `String`, your ID class should look like this:

```
public class Gfh_i18n_id implements Serializable {
  private String localeId = null;
  private String gfh = null;
  ...
}
```

Cannot use an @IdClass attribute for a @ManyToOne relationship

Solution

Problem