Question

我在一个类中有多个反向引用类。由于我使用@JsonBackReference，我收到错误。我为这些类分配了@JsonIdentityInfo注释，但我仍然得到同样的错误。

public class X implements Serializable {
  ....
  //bi-directional many-to-one association to Booking
  @ManyToOne(fetch = FetchType.EAGER)
  @JoinColumn(name = "xxA", nullable = false)
  @JsonBackReference
  private A a;

  //bi-directional many-to-one association to Client
  @ManyToOne(fetch = FetchType.EAGER)
  @JoinColumn(name = "xxB", nullable = false)
  @JsonBackReference
  private B b;
  ...getters setters
}

@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property = "@id")
public class B implements Serializable {
  ........ 
  //bi-directional many-to-one association to BookedClient
  @OneToMany(mappedBy = "b", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
  @JsonManagedReference
  private List < X > xxB;
  ........ getters setters
}


@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property = "@id")
public class A implements Serializable {
  ........
  //bi-directional many-to-one association to BookedClient
  @OneToMany(mappedBy = "a", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
  @JsonManagedReference
  private List < X > xxA;
  ........ getters setters
}

错误：

com.fasterxml.jackson.databind.JsonMappingException：具有名称＆＃39; defaultReference＆＃39;
的多个反向引用属性

如何解决此错误？我可以不在课堂上使用多个反向引用吗？

Answer 1

根据Jackson's javadoc，@JsonManagedReference和@JsonBackReference都接受将它们绑定在一起的名称值：

  @JsonBackReference("a")
  private A a;

  @JsonManagedReference("a")
  private List < X > xxA;

Answer 2

我也遇到过这个问题，但在最后我解决了这个问题。

//This is parent class
@Entity
@Table(name = "checklist")
@JsonIgnoreProperties("inspection")
public class Checklist implements java.io.Serializable {

    @ManyToOne
    @JoinColumn(name = "product_id", referencedColumnName = "id")
    @JsonBackReference
    private Product product;

    @OneToMany(mappedBy = "checklists", cascade = CascadeType.ALL)
    @JsonManagedReference
    private Set<Inspection> inspection = new HashSet<Inspection>();
//Constructor
//Getter and Setter
}

//This is child class
@Entity
@Table(name = "inspections")
public class Inspection {

    @ManyToOne
    @JoinColumn(name = "chk_id", referencedColumnName = "id")
    private Checklist checklists;
//Constructor
//Getter and Setter
}

在Parent class中提及@JsonIgnoreProperties("inspection")和@JsonManagedReference

解决了在同一个父类中使用两个@JSONBackRefrence引发的问题。

Answer 3

所以这确实花了我一段时间......

您可以使用 @JsonIdentityReference(alwaysAsId = true) 相应地注释您的引用，然后将其从主引用中删除

    @JsonIdentityReference(alwaysAsId = true)
    private Set<PackInstructionGroup> groups = new TreeSet<>();

具有名称＆＃39; defaultReference＆＃39;的多个反向引用属性

3 个答案: