无法评估表达式方法引发了“java.lang.StackOverflowError”异常。具有实体之间的嵌套关系

Question

我总有一天会遇到一个问题。 所以让我们开始吧。我有 3 个类，例如标签、优惠和动物

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "animals")
public class Animal {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "animal_id")
private Long id;

@Column(name = "name")
@NotNull
private String name;

@Column(name = "description")
@NotNull
private String text;

@Column(name = "quantity")
@NotNull
private int count;


@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "user_id", nullable = false)
private User user;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "tag_id", nullable = false)
private Tag tags;


@OneToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "offer_id", nullable = true)
private Offer offer;

优惠

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "offer")
public class    Offer {


@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "offer_id")
private Long id;

@Column(name = "title")
@NotNull
private String title;

@Column(name = "description")
@NotNull
private String text;


@Column(name = "price")
@NotNull
private int price;

@Column(name = "contact")
@NotNull
private int contact;

@Temporal(TemporalType.TIMESTAMP)
@Column(name = "create_date", nullable = false, updatable = false)
@CreationTimestamp
private java.util.Date createDate;



@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "user_id", nullable = false)
private User user;


@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "tag_id", nullable = false)
private Tag tags;


@OneToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "animal_id", nullable = false)
private Animal animal;

还有标签。

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "tags")
public class Tag {


@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "tag_id")
private long id;

@Column(name = "name")
@Email(message = "*Please provide a valid tag")
@NotEmpty(message = "*Please provide an tag")
private String name;


@OneToMany(mappedBy = "tags")
private Set<Offer> offers;

@OneToMany(mappedBy = "tags")
private Set<Animal> animals;

OneToOne 关系是因为我想为一只动物提供一个报价。

我也有控制器喜欢显示添加新的报价。

@RequestMapping(value = "/postForm", method = RequestMethod.GET)
public String newOffer(Principal principal,Model model) {

  String e_mail = principal.getName();
  System.out.println(e_mail);
  User user = userService.findUserByEmail(e_mail);

  Offer offer = new Offer();
  offer.setUser(user);
    Long id = user.getId();

    List<Tag> tags =  tagService.findAlltags();


   List<Animal> animal = animalRepository.findAnimalByUser(user);

    model.addAttribute("tags", tags);
    model.addAttribute("animals",animal);
    model.addAttribute("offer", offer);

        return "/postForm";
}

我正在传递诸如动物之类的列表，以及要选择标签的标签，以及分配给用户的动物。 我的动物仓库。

public interface AnimalRepository extends JpaRepository<Animal, Long> {


    List<Animal> findAnimalByUser(User user);


}

实际上，我在正确展示动物方面存在问题。标签显示正确，但动物列表无法评估动物类别内的标签。更具体地说，让我向您展示 Inteliji 的回溯屏幕

imgur 的链接enter link description here 关系可能有问题，但究竟是什么？感谢所有的答案。 :)

Answer 1

Animal 类中的toString() 方法会导致此问题。方法从Animal 和Tag 类交替构建返回字符串，这两个类都相互引用，产生无限过程。

去掉@Data注解（包括@ToString注解），自己实现toString()方法。

Answer 2

如果您使用的是 lombok，只需添加；

@EqualsAndHashCode(onlyExplicitlyIncluded = true, callSuper = false)