名为“defaultReference”的java多个反向引用属性

Question

我在一个课堂上有多个反向参考课。因为我对它们使用了@JsonBackReference，所以我得到了一个错误。我为这些类分配了@JsonIdentityInfo注释，但仍然得到相同的错误

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: Multiple back-reference properties with name 'defaultReference'

如何解决此错误？我不能在一个类中使用多个反向引用吗

Answer 1

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，然后将其保留在主引用之外

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

Answer 2

我也面临着这个问题，但最后我解决了

//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
}

通过在父类中提到@JsonIgnoreProperties("inspection")和@JsonManagedReference

解决了在同一父类中使用两个@JSONBackRefrence所引发的问题