java - 如何在@HandleBeforeSave 事件中获取旧实体值以确定属性是否已更改？

Question

我正在尝试在 @HandleBeforeSave 事件中获取旧实体。

@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());
    }
}

如果我尝试使用 findOne 方法获取旧实体，但这会返回新事件。可能是因为当前 session 中的 Hibernate/Repository 缓存。

有没有办法获取旧实体？

我需要这个来确定给定的属性是否被更改。如果属性发生变化，我需要执行一些操作。

Answer 1

如果使用 Hibernate，您可以简单地从 session 中分离新版本并加载旧版本:

@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
      }
   }
}