Question

I have 2 JPA entities that resemble the following:

@Entity
class Customer {
   @Id
   @GeneratedValue
   Long id

   @OneToOne(cascade = CascadeType.ALL)
   @PrimaryKeyJoinColumn
   CustomerInformation customerInformation
}


@Entity
class CustomerInformation {
   @Id
   @OneToOne
   @JoinColumn(name = "id")
   Customer customer

   String firstName
   String lastName
}

I’m using spring-data-jpa to generate my DAO layer. Here it is, though it’s not very interesting:

public interface CustomerRepository extends CrudRepository<Customer, Long> {
}

I’m calling this in a spring context and using @Transactional annotations to tell the JPA provider when to commit the transaction to the database. For testing, I grab the entity manager using @PersistenceContext and manually flush it to end the transaction. Due to the nature of our application, there may be a Customer that exists in the database without a customerInformation object associated with it. If I create a new customer and a customerInformation object in the same transaction, things work as I expect them. For example, this works:

@Transactional
public void createNewCustomer() {
   Customer cust = new Customer();
   CustomerInformation custInf = new CustomerInformation;
   custInf.setCustomer(cust);
   custInf.setFirstName("asdf");
   custInf.setLastName("hjkl");

   cust.setCustomerInformation(custInf);

   customerRepository.save(cust);
}

But if I want to update an existing customer, I run into an issue where it tries to insert the CustomerInformation object with a null id. For example, this fails miserably:

@Transactional
public void updateExistingCustomer(Long userId) {

   Customer foundCustomer = customerRepository.findOne(userId);

   if (foundCustomer.getCustomerInformation() == null) {
      CustomerInformation custInf = new CustomerInformation();
      custInf.setCustomer(foundCustomer);
      custInf.setFirstName("asdf");
      custInf.setLastName("hjkl");

      cust.setCustomerInformation(custInf);

      customerRepository.save(foundCustomer);
   }
}

This fails with the error message:

Hibernate: insert into CustomerInformation (firstName, lastName, id) values (?, ?, ?)
Feb 1, 2013 7:40:12 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
WARN: SQL Error: 20000, SQLState: 23502
Feb 1, 2013 7:40:12 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: Column 'ID'  cannot accept a NULL value.

Am I misunderstanding something? Any help is appreciated.

Thanks in advance!

Answer 1

I modified the entity to look like this:

@Entity
class CustomerInformation {

    @Id
    Long id

    @MapsId
    @OneToOne
    @JoinColumn(name = "id")
    Customer customer

    String firstName
    String lastName
}

And everything worked. As far as I could tell, both versions of CustomerInformation would have resulted in the same SQL, except the second version models the actual id, which I don’t necessarily need. I’ll expand this in another question, but the above code solved my problem.