Foreign key mapping inside Embeddable class

Question

I am using `eclipselink` for `JPA`. I have an entity, which has a composite key fabricated out of two fields. Following is my Embeddable primary key class' fields(members). ``` @Embeddable public class LeavePK { @ManyToOne(optional = false) @JoinColumn(name = "staffId", nullable = false) private Staff staff; @Temporal(TemporalType.TIMESTAMP) private Calendar date; //setters and getters } ``` My entity is going to hold leave data related to a staff, so I am trying to combine staff object and leave date to produce composite key. Apart from my logic, it is not allowing me to have a foreign key mapping inside embeddable class. When I try to use JPA tools--> Generate Tables From Entity, it gives error as below, which explains, but I am not getting it. ``` org.eclipse.persistence.exceptions.ValidationException Exception Description: The mapping [staff] from the embedded ID class [class rs.stapp.entity.LeavePK] is an invalid mapping for this class. An embeddable class that is used with an em…

Accepted Answer

Don't put relationships into ID classes, neither for `@IdClass` or `@EmbeddedId` ones. An `@Embeddable` class may only include the annotations `@Basic`, `@Column`, `@Temporal`, `@Enumerated`, `@Lob`, or `@Embedded`. Everything else is provider-specific syntax (e.g. Hibernate allows this, but since you're using EclipseLink, which is the JPA RI, I doubt this is what you want).

Here's an example JPA PK/FK mapping:

```
@Entity
@Table(name = "Zips")
public class Zip implements Serializable
{
    @EmbeddedId
    private ZipId embeddedId;

@ManyToOne
    @JoinColumn(name = "country_code", referencedColumnName = "iso_code")
    private Country country = null;

...
}

@Embeddable
public class ZipId implements Serializable
{
    @Column(name = "country_code")
    private String countryCode;

@Column(name = "code")
    private String code;

...
}
```

HTH

Foreign key mapping inside Embeddable class

Solution

Problem