JPA repository: Fetching CreationTimestamp after repository.save() returns null

I've the following structure:

• BaseEntity class
• Order entity which extends BaseEntity
• Address (embedded into Order)

When I'm saving an order to database, it gets saved with createdDate and lastModifiedDate automatically populated. After save, when I fetch the same order from database, createdDate and lastModifiedDate are returned as NULL. Why ?

BaseEntity.java

@MappedSuperclass
@Getter
@Setter
public abstract class BaseEntity {
  @Id
  @GeneratedValue(generator = "UUID")
  @GenericGenerator(name = "UUID", strategy = "org.hibernate.id.UUIDGenerator")
  @Column(length = 36, nullable = false)
  private UUID id;

  @CreationTimestamp
  @Column(name = "created_date", updatable = false)
  private Timestamp createdDate;

  @UpdateTimestamp
  @Column(name = "last_modified_date")
  private Timestamp lastModifiedDate;

OrderEntity.java

@Entity
@Builder
@NoArgsConstructor
@AllArgsConstructor
@Setter
@Getter
@Table(name = "order")
public class Order extends BaseEntity {

  private String customer;

  @Embedded
  private Address shippingAddress;

Below is the test that fails:

@SpringBootTest
class OrderRepositoryTest {

  @Autowired
  private OrderRepository orderRepository;

  @Test
  @Transactional
  @Rollback(value = false)
  public void test_saveOrderHeader() {
    final Order order = Order.builder()
            .customer("first buyer")
            .build();

    final OrderHeader savedOrder = orderRepository.save(order);

    final Optional<Order> fetchedOrder = orderRepository.findById(savedOrder.getId());

    assertNotNull(fetchedOrder);
    assertNotNull(fetchedOrder.get().getId());
    assertNotNull(fetchedOrder.get().getCreatedDate());   //test fails here, getting NULL
    assertNotNull(fetchedOrder.get().getLastModifiedDate());  //getting NULL
  }
}

Here is what I found during debugging:

savedOrder (debugging test): Note that fetchedOrder looks exactly same. In saved order, timestamp can be null because order hasn't been saved completely to DB yet. But in fetchedOrder (after savedOrder), it shouldn't be NULL.

But the order gets saved with timestamp in database (see below):

So what is going wrong here?

Hours later, I found the resolution. Here's what worked for me:
since the code that fails is repository test code, I have to use EntityManager as well. Doing entityManager.flush() after saving the Order to database resolved the issue.

Working code:

@SpringBootTest
class OrderRepositoryTest {

  @Autowired
  private OrderRepository orderRepository;

  @Autowired
  private EntityManager em; //added

  @Test
  @Transactional
  @Rollback(value = false)
  public void test_saveOrderHeader() {
    final Order order = Order.builder()
            .customer("first buyer")
            .build();

    final OrderHeader savedOrder = orderRepository.save(order);
    em.flush(); //added 
    final Optional<Order> fetchedOrder = orderRepository.findById(savedOrder.getId());

    assertNotNull(fetchedOrder);
    assertNotNull(fetchedOrder.get().getId());
    assertNotNull(fetchedOrder.get().getCreatedDate());   
    assertNotNull(fetchedOrder.get().getLastModifiedDate());
  }
}

</details>



# 答案2
**得分**: 0

以下内容也有效（我猜添加 "Transactional" 是问题所在）：

```java
@SpringBootTest
class OrderRepositoryTest {

  @Autowired
  private OrderRepository orderRepository;

  @Test
  public void test_saveOrderHeader() {
    final Order order = Order.builder()
            .customer("第一个买家")
            .build();

    final OrderHeader savedOrder = orderRepository.save(order);
    final Optional<Order> fetchedOrder = orderRepository.findById(savedOrder.getId());

    assertNotNull(fetchedOrder);
    assertNotNull(fetchedOrder.get().getId());
    assertNotNull(fetchedOrder.get().getCreatedDate());   
    assertNotNull(fetchedOrder.get().getLastModifiedDate());
  }
}

@SpringBootTest
class OrderRepositoryTest {

  @Autowired
  private OrderRepository orderRepository;

  @Test
  public void test_saveOrderHeader() {
    final Order order = Order.builder()
            .customer("first buyer")
            .build();

    final OrderHeader savedOrder = orderRepository.save(order);
    final Optional<Order> fetchedOrder = orderRepository.findById(savedOrder.getId());

    assertNotNull(fetchedOrder);
    assertNotNull(fetchedOrder.get().getId());
    assertNotNull(fetchedOrder.get().getCreatedDate());   
    assertNotNull(fetchedOrder.get().getLastModifiedDate());
  }
}