无法创建复合主键：无法构建 Hibernate SessionFactory

Question

I try to create a composite primary key but can't.

My attempt (there is the tutorial I used):

• User entity:

@Entity
@Table(name = "user")
public class User {

    @Id
    @Column
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;
    @Column
    private String name;

    //getters, setters, equals, hashcode
}

• PersonalScore class:

@Entity
public class PersonalScore {

    @EmbeddedId
    private PersonalScoreId personalScoreId;
    //getters, setters, equals, hashcode, constructors
}

• PersonalScoreId class (Primary key):

@Embeddable
public class PersonalScoreId implements Serializable {
    
    private User user;
    private Date date;

    //getters, setters, equals, hashcode, constructors (noargs included)

That's all. In the result I got the error:

> Caused by: javax.persistence.PersistenceException: [PersistenceUnit:
> default] Unable to build Hibernate SessionFactory; nested exception is
> org.hibernate.MappingException: Could not determine type for:
> com...model.dto.User, at table: personal_score, for columns:
> [org.hibernate.mapping.Column(user)]

Answer 1

From EmbeddedId :

Relationship mappings defined within an embedded id class are not supported.

What you need to do is replace the User field with a field for the user's id ( private long userId ), then use MapsId in your PersonalScore class to add a relation with User using the userId field from the embedded id.