CODEWITHSUNDEEP
javahibernatejackson
user2316219
user2316219

Reputation: 334

@jsonbackreference doesn't bind relationship

I have two classes:

Person.java:

@Entity
@PrimaryKeyJoinColumn(name="owner_id")
public class Person extends Owner {

    @ManyToOne
    @JoinColumn(name = "car_sharing_id")
    @JsonBackReference
    private CarSharing carSharing;
}

CarSharing.java:

@Entity
public class CarSharing extends MetadataEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @OneToOne
    @JoinColumn(name = "owner_id", nullable = false)
    @NotNull
    private Person owner;

    @OneToMany(mappedBy = "carSharing", cascade = CascadeType.ALL)
    @Valid
    private Set<Person> members;
}

I am using @JsonBackReference to avoid infinite cycles. The CarSharing class is working fine the problem only happens to the Person class.

Getting the person seems to ignore the carSharing property. As it is null when coming back to the server the update is unlinking the reference to the carsharing_id in the person table.

Stopping the loop is fine but i would also need the carSharing available in the Person class.

Any idea how to solve this?

Upvotes: 2

Views: 1972

Answers (1)

Meiko Rachimow
Meiko Rachimow

Reputation: 4724

If you are using Jackson 2.x, you can use the Annotation @JsonIdentityInfo:

Whether Object Identity information is to be used for determining how to serialize/deserialize property value to/from JSON (and other data formats) will be based on existence (or lack thereof) of @JsonIdentityInfo annotation.
see: http://wiki.fasterxml.com/JacksonFeatureObjectIdentity

For example, if you annotate the class CarSharing:

import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
//...
@JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class, property="@id")
public class CarSharing {

the JSON result of a person (I added a field name to this class) is:

  {
    "carSharing": {
      "@id": 1,
      "id": 12345,
      "owner": {
        "carSharing": 1,
        "name": "owner"
      },
      "members": [
        {
          "carSharing": 1,
          "name": "owner"
        },
        {
          "carSharing": 1,
          "name": "driver2"
        },
        {
          "carSharing": 1,
          "name": "driver"
        }
      ]
    },
    "name": "driver2"
  }

And a CarSharing instance with id=12345:

  {
    "@id": 1,
    "id": 12345,
    "owner": {
      "carSharing": 1,
      "name": "owner"
    },
    "members": [
      {
        "carSharing": 1,
        "name": "owner"
      },
      {
        "carSharing": 1,
        "name": "driver2"
      },
      {
        "carSharing": 1,
        "name": "driver"
      }
    ]
  }

The field @id is generated from jackson. If the referenced object is not serialized, the value is set to the @id of the referenced object.

Upvotes: 1

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