Question

I’m having a problem creating a parent and child object and persisting them in one go to the database using JPA and hibernate. The parent class looking like this:

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

    @Id
    @Column(name = "ID", unique = true, nullable = false, updatable = false)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

}

The child object uses a compound key, one of fields being the ID of the parent:

@Entity
@Table(name = "PAttribute")
public final class Attribute {

   @EmbeddedId
    @AttributeOverrides({
                    @AttributeOverride(name = "domain", column = @Column(name = "domain", nullable = false, length = 128)),
                    @AttributeOverride(name = "name", column = @Column(name = "name", nullable = false, length = 128)),
                    @AttributeOverride(name = "userid", column = @Column(name = "userid", nullable = false)) })
    private AttributePk pk;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "userid", nullable = false, insertable = false, updatable = false)
    private User user;

}

The composite key class being:

    @Embeddable
    public class AttributePk implements java.io.Serializable {

            private static final long serialVersionUID = -7003721226789641149L;

            @Column(nullable = false, length = 128)
            private String domain;

            @Column(nullable = false, length = 128)
            private String name;

            @Column(nullable = false)
            private long userid;

    }

Now when I create a new User and add an Attachment, and then attempt to save the object graph

    User user = new User("[e-mail]", "xyz");
    user.setScreenName("joe1bloggs");
    user.addAttribute("domain", "name", 212);

    target.saveAndFlush(user);  

I get the exception

    Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`fta_portal_user/PAttribute`, CONSTRAINT `userId` FOREIGN KEY (`userid`) REFERENCES `PUser` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

Obviously the Attribute child object doesn’t have the ID of the user object set.

I know I can do the following, which works, but it seems odd that I can’t just create an object hierarchy and Hibernate work out how to set the IDs accordingly. I suspect that there’s no way round this as saveAndFlush() returns a new instance rather than just updating the input parameter version.

    User user = new User("[e-mail]", "xyz");
    user.setScreenName("joe1bloggs");

    // target is an JpaRepository intergafe
    user = target.saveAndFlush(user);

    user.addAttribute("domain", "name", 212);

    target.saveAndFlush(user);

Anyone have any ideas or is it just a case of living with it?

Thanks

Nick

EDIT: You can get this to work by adding the @MapsId annotation to the child class (thanks to axtavt’s reply). i.e.

    @MapsId("userId")
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "userId", nullable = false, insertable = false, updatable = false)
    private User user;

Answer 1

Have you tried to map it as follows:

@ManyToOne(fetch = FetchType.LAZY)     
@MapsId("userid")
private User user; 

As far as I understand in this case userid field of AttributePk should be populated with the id of user automatically.