Searching proper way to convert my two-way linkage between objects to JSON format

Question

I stuck searching proper way to convert my Student object (with nested Marks object) to JSON format.

I tried to combine fetch type

Answer 1

You should use JsonBackReference annotation. I have simplified your code only to Jackson annotation to show how it works. Model:

@JsonPropertyOrder({"studentId", "studentName", "ctlgMarks"})
class Students {

    private int studentId;
    private String studentName;
    private Marks ctlgMarks;

    // getters, setters, constructors
}

class Marks {

    private int marksId;
    private String markValue;

    @JsonBackReference
    private Set<Students> students;

    // getters, setters, constructors
}

Example usage:

import com.fasterxml.jackson.annotation.JsonBackReference;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class JsonApp {

    public static void main(String[] args) throws Exception {
        Marks marks = new Marks();
        Students student0 = new Students(1, "Rick", marks);
        Students student1 = new Students(2, "Morty", marks);

        marks.setMarksId(1);
        marks.setMarkValue("Value");
        marks.setStudents(new HashSet<>(Arrays.asList(student0, student1)));

        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);

        System.out.println(mapper.writeValueAsString(student0));
        System.out.println(mapper.writeValueAsString(student1));
        System.out.println(mapper.writeValueAsString(marks));
    }
}

Above code prints. Student 1:

{
  "studentId" : 1,
  "studentName" : "Rick",
  "ctlgMarks" : {
    "marksId" : 1,
    "markValue" : "Value"
  }
}

Student 2:

{
  "studentId" : 2,
  "studentName" : "Morty",
  "ctlgMarks" : {
    "marksId" : 1,
    "markValue" : "Value"
  }
}

Marks:

{
  "marksId" : 1,
  "markValue" : "Value"
}