JPA 生成失败并显示 JSON

Question

我找不到任何解决方案来解决这个问题，所以我决定创建一个新问题。我有一个简单的类

@Entity
public class Reservation {

// private Integer RESERVATION_ID;
// private Integer id;
private long code;
private Date date;
private Client reservationClient;
private WashType reservationWashType;
private Vehicle reservationVehicle;
private Wash reservationWash;
private Worker reservationWorkerPesel;
private Review reservationReview;
private ReservationReminder reservationReminder;
 }

我在哪里运行这样的查询：

  @Query("SELECT r FROM Reservation r JOIN FETCH r.reservationReminder where r.reservationWorkerPesel = :worker")
List<Reservation> findByReservationWorkerPesel(@Param("worker") Worker worker);

起初我看起来一切都很好，但后来我做了一些类似的操作：

    public List<ReservationReminder> findByReservationWorkerPesel(Worker worker) {
    List<ReservationReminder> reservationReminderList = new ArrayList<>();
    List<Reservation> byReservationWorkerPesel = reservationDao.findByReservationWorkerPesel(worker);
    for (Reservation r : byReservationWorkerPesel) {
        if (r.getReservationReminder() != null && r.getReservationReminder().getChecked() == false)
            reservationReminderList.add(r.getReservationReminder());
    }
    return reservationReminderList;
}

然后，当我看到 JSON 的样子时——这很奇怪，因为：

[{"reservationReminderId":2,"reservation":{"code":263022,"date":1487851200000,"reservationClient":{"clientPesel":"91122619197","name":"Client 1", "surname":"Client 1","email":"client@wp.pl","phone":"234567890","accountNumber":"34567897654345678987654356","clientUser":{"userId":3,"login ":"client","passwordHash":"$2a$10$0jJMMzeh2CTRagk3hwRSlurx.mxLgR1aAUQOYBD9QFqbISeoTSVN。","userRole":{"roleId":3,"name":"CLIENT","users":[{"userId": 8,"login":"clien5","passwordHash":"$2a$10$6WrmwpwOdhv6UXBo2mYq8ucKiQTwvIwTHw23myo6.oujflh8pqKR.","userRole":{"roleId":3,"name":"CLIENT","users":[{ "userId":8,"login":"clien5","passwordHash":"$2a$10$6WrmwpwOdhv6UXBo2mYq8ucKiQTwvIwTHw23myo6.oujflh8pqKR.","userRole":{"roleId":3,"name":"CLIENT","users ":[{"userId":8,"login":"clien5","passwordHash":"$2a$10$6WrmwpwOdhv6UXBo2mYq8ucKiQTwvIwTHw23myo6.oujflh8pqKR.","userRole":{"roleId":3,"name":"CLIENT ","users":[{"userId":8,"login":"clien5","passwordHash":"$2a$10$6WrmwpwOdhv6UXBo2mYq8ucKiQTwvIwTHw23myo6.oujflh8pqKR.","us erRole":{"roleId":3,"name":"CLIENT","users":

....

[{"userId":8,"login":"clien5","passwordHash":"$2a$10$6WrmwpwOdhv6UXBo2mYq8ucKiQTwvIwTHw23myo6.oujflh8pqKR.","userRole":{"roleId":3,"name":" CLIENT","users":[{"userId":8,"login":"clien5","passwordHash":"$2a$10$6WrmwpwOdhv6UXBo2mYq8ucKiQTwvIwTHw23myo6.oujflh8pqKR.","userRole":{"roleId":3," name":"CLIENT","users":[{"userId":8,"login":"clien5","passwordHash":"$2a$10$6WrmwpwOdhv6UXBo2mYq8ucKiQTwvIwTHw23myo6.oujflh8pqKR.","userRole":{"roleId" :3,"name":"CLIENT","users":[{"userId":8,"login":"clien5","passwordHash":{"timestamp":1489015140465,"status":200,"error ":"OK","exception":"org.springframework.http.converter.HttpMessageNotWritableException","message":"无法写入内容：无限递归(StackOverflowError)（通过引用链：com.carwash.domains.User[ \"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\ "]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentB ag[0]->com.carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0] ->com.carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0]->com. carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains。用户[\"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\" userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\"] ->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\"]->com. carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\"]->com.carwash.domains。角色[\"用户\"]-

...

\"]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\ "]->org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\"]-> org.hibernate.collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate。 collection.internal.PersistentBag[0]->com.carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal。 PersistentBag[0]->com.carwash.domains.User[\"userRole\"]->com.carwash.domains.Role[\"users\"]->org.hibernate.collection.internal.PersistentBag[0] ->com.carwash.domains.User[\"userRole\"])","path":"/api/reservationreminder"}

我做错了什么？

也许它可以告诉你一些事情 - 我不知道为什么在制作了一个 GET 方法（仅获取）之后我得到了一些错误？

Answer 1

在 User 和 UserRole 对象之间有一个 Infinite recursion。每当用户被序列化时，他的相关用户角色也会被序列化。由于用户角色也确实与用户有关系，因此您具有递归。

对此的解决方案可能是使用@JsonManagedReference（添加到User 中的关系）和@JsonBackReference（在UserRoles 中的realtion）。也可以在这里查看：Infinite Recursion with Jackson JSON and Hibernate JPA issue

@Entity
public class User
   ...
   @JsonManagedReference
   private Set<UserRole> userRoles;


@Entity
public class UserRole
   ...
   @JsonBackReference
   private User user;

@JsonManagedReference 意味着在序列化过程中会考虑到关系部分。所以相关的用户角色也会被序列化。由于那里的相关连接标有@JsonBackReference 序列化停止进一步。

Answer 2

@KLHauser

如果我有课，如何管理这个案例

@Entity
public class ReservationReminder {
private int reservationReminderId;
private Reservation reservation;
private boolean isChecked;
private Date checkedDate;

和预订类

@Entity
public class Reservation {

// private Integer RESERVATION_ID;
// private Integer id;
private long code;
private Date date;
private Client reservationClient;
private WashType reservationWashType;
private Vehicle reservationVehicle;
private Wash reservationWash;
private Worker reservationWorkerPesel;
private Review reservationReview;
private ReservationReminder reservationReminder;

@Entity
public class Worker {

private String workerPesel;
private String name;
private String surname;
private Date startDateWorking;
private String accountNumber;
private List<Review> workerReview;
private Adress workerAdress;
private List<LaborHistory> workerLaborHistory;
private Wash workerWash;
//private List<WorkerWorkerTime> workerWorkTime;
// private Role WORKER_ROLE;
private User workerUser;
private List<Reservation> workerReservation;

我想用 Reservation 类的 Worker 加载 ReservationReminder 类？如果我像这样使用@JsonIgonre

@OneToOne(mappedBy = "reservationReminder", fetch = FetchType.LAZY)
@JsonIgnore
public Reservation getReservation() {
    return reservation;
}

我只从 ReservationReminder 得到了一个带有 checkDate、isChecked 和 reservationReminderId 的 Json