How can I parse nested JSON with multiple wrapper classes? (spring boot project)

Question

Make a sample Java service which takes the following json from an endpoint as input, parses it and puts it into the database.

1. Input: ​ The input will have a fixed format which will be posted as a content body to the endpoint.

2. Output: ​ The output should be a number of rows that are filled in the database or error in case of failures.

Sample input :

   {
    "quiz": {
        "sport": {
              "q1": {
                  "question": "Which one is correct team name in NBA?",
                  "options": [
                        "New York Bulls",
                        "Los Angeles Kings",
                        "Golden State Warriros",
                        "Huston Rocket"
                        ],
                 "answer": "Huston Rocket"
                    }
                  },
         "maths": {
               "q1": {
                   "question": "5 + 7 = ?",
                   "options": [
                            "10",
                            "11",
                            "12",
                            "13"
                           ],
                    "answer": "12"
                     },
                "q2": {
                    "question": "12 - 8 = ?",
                    "options": [
                              "1",
                              "2",
                              "3",
                              "4"
                             ],
                     "answer": "4"
                      }
                   }
               }
          }

I've created a basic Rest service with springboot that takes in question, options and answer as input, and also displays it in the same way.

Ex. input :

   { 
     "question": "khis is the question part",
        "options": [
            "option 1",
            "option 2",
            "option 3",
            "option 4"
            ],
        "answer": "option 1"
       }

I have created a springboot project and created the following java classes: 1. QuestionSet.java

package com.example.demo.questionset;

import java.io.Serializable;

import com.fasterxml.jackson.annotation.JsonRootName;



public class QuestionSet {

    private String question;
    private String options[];
    private String answer;


    public QuestionSet() {

    }




public QuestionSet(String question, String[] options, String answer) {
        super();
        this.question = question;
        this.options = options;
        this.answer = answer;
    }


    public String getQuestion() {
        return question;
    }
    public String[] getOptions() {
        return options;
    }
    public String getAnswer() {
        return answer;
    }
    public void setQuestion(String question) {
        this.question = question;
    }
    public void setOptions(String[] options) {
        this.options = options;
    }
    public void setAnswer(String answer) {
        this.answer = answer;
    }
    }

`

2. QuestionSetService.java

   package com.example.demo.questionset;
   
   import java.util.ArrayList;
   import java.util.Arrays;
   import java.util.List;
   
   import org.springframework.http.HttpStatus;
   import org.springframework.http.ResponseEntity;
   import org.springframework.stereotype.Service;
   import org.springframework.web.bind.annotation.PostMapping;
   import org.springframework.web.bind.annotation.RequestBody;
   
   import com.fasterxml.jackson.annotation.JsonProperty;
   import com.fasterxml.jackson.databind.ObjectWriter;
   
   
   @Service
   public class QuestionSetService {
   
   
   
   
   String nameString[] = {"kabir", "ram", "shyam", "varun"};
   

3. QuestionSetController.java

package com.example.demo.questionset;

 import java.util.List;



import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.fasterxml.jackson.annotation.JsonGetter;

   @RestController
   public class QuestionSetController {

@Autowired
QuestionSetService questionSetService;


@RequestMapping("/questionsets")
public List<QuestionSet> getAllQuestionSets(){
    return questionSetService.getAllQuestionSets();
}

@RequestMapping("/questionsets/{question}")
public QuestionSet getQuestionSetByQuestion(@PathVariable String question)
 {
    return questionSetService.getQuestionSetByQuestion(question);
}

@PostMapping("/questionsets")
public void postController(
  @RequestBody QuestionSet questionSet) {

    questionSetService.addQuestionSet(questionSet);
}

  }





    private List<QuestionSet> questionSets = null;


    public List<QuestionSet> getAllQuestionSets() {
        return questionSets;
    }

    public QuestionSet getQuestionSetByQuestion(String question) {
        return questionSets.stream().filter(t ->             
    t.getQuestion().equals(question)).findFirst().get();
    }


    public ResponseEntity addQuestionSet( QuestionSet questionSet) {
        questionSets.add(questionSet);
        return ResponseEntity.ok(HttpStatus.OK);
    }

     }

I can take in simple json input in the form of questionset but the required json input is much more complex. I understand that I need to make wrapper classes and use objectmapper, but I don't know how.

Answer 1

            JSONObject obj = (JSONObject) parser.parse(reader);
            JSONObject response =(JSONObject) parser.parse(obj.get("quiz").toString());
            JSONObject sub =(JSONObject) parser.parse(response.get("sport").toString());
            JSONObject q1 = (JSONObject) parser.parse(sub.get("q1").toString());
            String question =(q1.get("question").toString());
            System.out.println(question);
            JSONArray options = (JSONArray)parser.parse(q1.get("options").toString());
            for(int i=0 ;i<options.size();i++) {
                System.out.println(options.get(i));
            }


Output :-
      Which one is correct team name in NBA?
      New York Bulls
      Los Angeles Kings
      Golden State Warriros
      Huston Rocket

This is a sample on how you can parse the input json using simple-json. Although there is a lot of manual work here, you can avoid it by using nested JSONArray and iterate over it.