“直接自我参照导致循环”杰克逊与继承

Question

I have a class something like this:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Audited
@DiscriminatorColumn(name = "tipo_hito")
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder = { "idHito" })
@XmlRootElement(name = "Hito")
public abstract class Hito implements Ordenable {
    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    @Column(name = "idhito", nullable = false)
    private Long idHito;

    public Long getIdHito() { return idHito; }

    public void setIdHito(Long idHito) { this.idHito = idHito; }
}

And a class that extends the class above

@MappedSuperclass
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder = {..., "successors", "predecessors", ...})
@XmlRootElement(name = "HitoOrdenable")
public abstract class HitoOrdenable extends Hito {

    @XmlElement(name = "predecessors")
    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(name = "succession", joinColumns = { @JoinColumn(name = "idpredecessor") }, inverseJoinColumns = { @JoinColumn(name = "idsuccessor") })
    private Set<Hito> predecessors;

    @XmlElement(name = "successors")
    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(name = "succession", joinColumns = { @JoinColumn(name = "idsuccessor") }, inverseJoinColumns = { @JoinColumn(name = "idpredecessor") })
    private Set<Hito> successors;

    // More code...
}

Now, the error it's when I try to get a HitoOrdenable . Because for example I can have:

Hito1
  Hito2-SuccessorOf1
  Hito3-SuccessorOf1
    Hito4-SuccessorOf3
Hito5
  Hito6-SuccessorOf5

So, when I get Hito1 this has Successors Hito2 and Hito3 . But when I get Hito2 it has predecessor Hito1 . So start a "infinite cycle".

The exact error is:

com.fasterxml.jackson.databind.JsonMappingException: Direct self-reference leading to cycle (through reference chain: ar.gob.buenosaires.esb.domain.message.ProyectoRespMsg["proyectos"]->java.util.ArrayList[5]->ar.gob.buenosaires.domain.Proyecto["obras"]->org.hibernate.collection.internal.PersistentBag[0]->ar.gob.buenosaires.domain.Obra["hitos"]->org.hibernate.collection.internal.PersistentBag[0]->ar.gob.buenosaires.domain.HitoObra["hitoOrdenable"])

I tried to set @JsonIgnore in predecessors but it doesn't works.

Answer 1

After a few days of trys. The only solution than we find was to add in @JsonIgnoreProperties({"predecessors"}) and @JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="idHitoAux")

HitoOrdenable.java

  @MappedSuperclass
  @XmlType(propOrder = {..., "successors", "predecessors", ...})
  @XmlAccessorType(XmlAccessType.FIELD)
  @JsonIgnoreProperties({ "predecessors" })
  @JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="idHitoAux")

Hito.java

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@Audited
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder = { "idHito", "tipoHito"})
@JsonIgnoreProperties({"idHitoAux", "hibernateLazyInitializer", "handler"})
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, visible = true, property = "tipoHito")
@JsonSubTypes({
        @JsonSubTypes.Type(name = "hito_obra", value = HitoObra.class),
        @JsonSubTypes.Type(name = "hito_proyecto", value = HitoProyecto.class)
})<

With JsonIgnoreProperties we prevent infinite cycle between sucessors and predecessors and with @JsonIdentityInfo it was because if we use "idHito" instead of "idHitoAux" (who its equals to idHito) Hibernate transformed idHito to null. So with "idHitoAux" Hibernate can identify every object in the List.

PD: After that solution we had a problem with deserialization of abstract class Hito , so our solution it wass to add @JsonSubTypes .

Greetings!