jackson deserialization with 2 fields self referencing the same class (self-reference cycle)

Question

I have below class referencing to itself:

@Entity
@Inheritance(strategy = TABLE_PER_CLASS)
//@JsonIdentityInfo(property="rowId", generator = ObjectIdGenerators.PropertyGenerator.class)
public abstract class AbstractEntity implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 568799551343430329L;

    @OneToOne(optional=false, fetch=FetchType.EAGER)
    @JoinColumn(name="createdBy")
    protected User createdBy;
    @OneToOne(optional=false, fetch=FetchType.EAGER)
    @JoinColumn(name="lastUpdatedBy")
    protected User lastUpdatedBy;

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    @Column(unique = true, nullable = false, updatable = false, length = 7)
    private Integer rowId;

    public User getCreatedBy() {
        return this.createdBy;
    }

    public void setCreatedBy(User createdBy) {
        this.createdBy = createdBy;
    }

    public User getLastUpdatedBy() {
        return this.lastUpdatedBy;
    }

    public void setLastUpdatedBy(User lastUpdatedBy) {
        this.lastUpdatedBy = lastUpdatedBy;
    }

    public Integer getRowId() {
        return this.rowId;
    }

    public void setRowId(Integer RowId) {
        this.rowId = RowId;
    }

    public String toString() {
        return "[Id]:" + this.rowId + " - [CreatedBy]:" + this.createdBy;
    }
}

Then I have a class User extending this class and a RepositoryUser interface:

public interface RepositoryUser extends CrudRepository<User, Integer> {

}

And a Controller:

@Controller
@RequestMapping(path = "/user")
public class ServiceUser {
    @Autowired
    private RepositoryUser repositoryUser;

    @GetMapping(path="/all", produces = "application/json; charset=UTF-8", headers = "Accept=application/json")
    public @ResponseBody Iterable<User> getAllUsers() {
        return repositoryUser.findAll();
    }

    @PostMapping(path="/add", consumes="application/json")
    public @ResponseBody User createOneUser(@RequestBody User user) {
        System.out.println(user);
        return repositoryUser.save(user);
    }
}

My issue is that I'm making reference to User twice (createdby and lastupdatedby) in the same class and either I tried JSonIdentityInfo, Jsonmanaged,jsonback nothing works. correctly.

I need to be able to have { User 1 data including created by and last updated by User 2 data including created by and last updated by }

and when I add I need to set the user who creates the record.

Can you please help me ?

Thanks a lot!

Answer 1

You could write/try a Custom Serializer Using StdSerializer.

Example of CustomJsonSerializer. NB: Did not run the code.

public class CustomJsonSerializer extends StdSerializer<AbstractEntity> {

  public CustomJsonSerializer() {
    this(null);
  }

  public CustomJsonSerializer(Class<AbstractEntity> t) {
    super(t);
  }

  @Override
  public void serialize(AbstractEntity value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException {
    Field[] fields = value.getClass().getDeclaredFields();
    jgen.writeStartObject();

    for (Field field : fields) {
        field.setAccessible(true);

       try {
           // Do the proper field mapping for field types . Object type example
           jgen.writeObjectField(field.getName(), field.get(value));

        } catch (Exception e) {
          // catch error
        }
    }

    jgen.writeEndObject();
  }
}

Then on your Rest Method use @JsonSerialize

@JsonSerialize(using = CustomJsonSerializer.class)
@GetMapping(path="/all", produces = "application/json; charset=UTF-8", headers = "Accept=application/json")
public @ResponseBody Iterable<User> getAllUsers() {
    return repositoryUser.findAll();
}

Please see Custom Serializer And StdSerializer

Possible different solution jackson-bidirectional infinite-recursion