多对一关系返回子对象的NULL列表

Question

我有2节课。 USER类和ORDER类。 订单类具有与@ManyToOne关系的User对象。 当RestController使用@PostMapping检索Order对象插入后的Order对象时，它将为嵌套的User对象返回空值

Rest Controller

$methodname

}

订单类

@RestController
public class OrderController {

@PersistenceContext
EntityManager entityManager;

@Transactional
@PostMapping(value = "api/v1/create/order")
public Order createOrder(@RequestBody Order order){

    entityManager.persist(order);
    return order;

}

用户类别

@Entity
@Table(name = "booking_order")
public class Order {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
Integer orderID;
@Column
String transactionAmount;
@Column
@CreationTimestamp
@Temporal(TemporalType.TIMESTAMP)
Date bookingTimestamp;
@ManyToOne
User user;


public Order(){}

public Integer getOrderID() {
    return orderID;
}

public void setOrderID(Integer orderID) {
    this.orderID = orderID;
}

public String getTransactionAmount() {
    return transactionAmount;
}

public void setTransactionAmount(String transactionAmount) {
    this.transactionAmount = transactionAmount;
}

public Date getBookingTimestamp() {
    return bookingTimestamp;
}

public void setBookingTimestamp(Date bookingTimestamp) {
    this.bookingTimestamp = bookingTimestamp;
}

public User getUser() {
    return user;
}

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

输入JSON

{     “ transactionAmount”：“ 100.50”，     “用户”：{         “ id”：1     } }

订单响应

{     “ orderID”：1     “ transactionAmount”：“ 100.50”，     “ bookingTimestamp”：“ 2019-05-15T20：44：43.234 + 0000”，     “用户”：{         “ id”：1         “用户名”：null，         “密码”：null     } }