Question

I’m trying to set up the following tables using JPA/Hibernate:

User:

userid - PK
name 

Validation:

userid - PK, FK(user)
code

There may be many users and every user may have max one validation code or none.

Here’s my classes:

public class User 
{
    @Id
    @Column(name = "userid") 
    @GeneratedValue(strategy = GenerationType.IDENTITY)    
    protected Long userId;

    @Column(name = "name", length = 50, unique = true, nullable = false)
    protected String name;

    ...
}

public class Validation 
{
    @Id
    @Column(name = "userid")
    protected Long userId;

    @OneToOne(cascade = CascadeType.ALL)
    @PrimaryKeyJoinColumn(name = "userid", referencedColumnName = "userid")
    protected User user;

    @Column(name = "code", length = 10, unique = true, nullable = false)
    protected String code;

    ...

    public void setUser(User user)
    {
        this.user = user;
        this.userId = user.getUserId();
    }

    ...
}

I create a user and then try to add a validation code using the following code:

public void addValidationCode(Long userId)
{   
    EntityManager em = createEntityManager();
    EntityTransaction tx = em.getTransaction();

    try 
    {
        tx.begin();

        // Fetch the user
        User user = retrieveUserByID(userId);

        Validation validation = new Validation();
        validation.setUser(user);
        em.persist(validation);
        tx.commit();
    }
    ...
}

When I try to run it I get a org.hibernate.PersistentObjectException: detached entity passed to persist: User

I have also tried to use the following code in my Validation class:

public void setUserId(Long userId)
{
    this.userId = userId;
}

and when I create a validation code I simply do:

Validation validation = new Validation();
validation.setUserId(userId);
em.persist(validation);
tx.commit();

But then since User is null I get org.hibernate.PropertyValueException: not-null property references a null or transient value: User.code

Would appreciate any help regarding how to best solve this issue!

Answer 1

If you use Hibernate you can also use

public class Validation {

    private Long validationId;
    private User user;

    @Id
    @GeneratedValue(generator="SharedPrimaryKeyGenerator")
    @GenericGenerator(name="SharedPrimaryKeyGenerator",strategy="foreign",parameters =  @Parameter(name="property", value="user"))
    @Column(name = "VALIDATION_ID", unique = true, nullable = false)
    public Long getValidationId(){
        return validationId;
    }

    @OneToOne
    @PrimaryKeyJoinColumn
    public User getUser() {
        return user;
    }

}

Hibernate will make sure that the ID of Validation will be the same as the ID of the User entity set.