java - How to get old entity value in @HandleBeforeSave event to determine if a property is changed or not?

Question

I'm trying to get the old entity in a @HandleBeforeSave event.

@Component
@RepositoryEventHandler(Customer.class)
public class CustomerEventHandler {

    private CustomerRepository customerRepository;

    @Autowired
    public CustomerEventHandler(CustomerRepository customerRepository) {
        this.customerRepository = customerRepository;
    }

    @HandleBeforeSave
    public void handleBeforeSave(Customer customer) {
        System.out.println("handleBeforeSave :: customer.id = " + customer.getId());
        System.out.println("handleBeforeSave :: new customer.name = " + customer.getName());

        Customer old = customerRepository.findOne(customer.getId());
        System.out.println("handleBeforeSave :: new customer.name = " + customer.getName());
        System.out.println("handleBeforeSave :: old customer.name = " + old.getName());
    }
}

In the event I try to get the old entity using the findOne method but this return the new event. Probably because of Hibernate/Repository caching in the current session.

Is there a way to get the old entity?

I need this to determine if a given property is changed or not. In case the property is changes I need to perform some action.

Answer 1

If using Hibernate, you could simply detach the new version from the session and load the old version:

@RepositoryEventHandler 
@Component
public class PersonEventHandler {

  @PersistenceContext
  private EntityManager entityManager;

  @HandleBeforeSave
  public void handlePersonSave(Person newPerson) {
      entityManager.detach(newPerson);
      Person currentPerson = personRepository.findOne(newPerson.getId());
      if (!newPerson.getName().equals(currentPerson.getName)) {
          //react on name change
      }
   }
}