org.hibernate.MappingException - 复合 id

Question

In my Spring boot - JPA application, I am trying to implement composite key :

@Entity
public class User 
{
    @Id
    private String timeStamp;
    @Id
    private String firstName;
    @Id
    private String lastName;
}

This gives me error, saying :

Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: Composite-id class must implement Serializable: com.mua.testkeys.model.User

Even if I implement Serializable it gives me error.

How can I resolve this ?

Used : Spring + JPA + H2

Answer 1

Composite Key can be created with @IdClass as below.
User.class

@IdClass(UserPK.class)
@Table(name = "user")
@Entity
public class User {
    @Id
    private String timeStamp;
    @Id
    private String firstName;
    @Id
    private String lastName;
//remaining fields
// getters and setters
}

UserPK.class

public class UserPK {
    private String timeStamp;
    private String firstName;
    private String lastName;
// constructors
// getters and setters
//implement euquels() and hashcode()
}

1. Define a Class for primary key with all keys as fields.
2. Implement equals() and hashcode() methods.
3. Annotate User class with @IdClass(UserPK.class)
4. Declare Id fields with @Id annotation