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How to get the level of each object in json, where objects can have any number of children of the same type of object

I have an Employee level structure as shown below. enter image description here

This structure is populated and saved using json like this

 {
  "name": "Lao Lao",
  "title": "general manager",
  "children": [
    {
      "name": "Bo Miao",
      "title": "department manager",
      "children": [
        {
          "name": "Li Jing",
          "title": "senior engineer"
        },
        {
          "name": "Li Xin",
          "title": "senior engineer",
          "children": [
            {
              "name": "To To",
              "title": "engineer"
            },
            {
              "name": "Fei Fei",
              "title": "engineer"
            },
            {
              "name": "Xuan Xuan",
              "title": "engineer"
            }
          ]
        }
      ]
    },
    {
      "name": "Su Miao",
      "title": "department manager",
      "children": [
        {
          "name": "Pang Pang",
          "title": "senior engineer"
        },
        {
          "name": "Hei Hei",
          "title": "senior engineer",
          "children": [
            {
              "name": "Xiang Xiang",
              "title": "UE engineer"
            },
            {
              "name": "Dan Dan",
              "title": "engineer"
            },
            {
              "name": "Zai Zai",
              "title": "engineer"
            }
          ]
        }
      ]
    }
  ]
}

I want to parse this Json to get all objects with level and parent name like this

{name =  Lao lao , parent = null , level = 1 }
{name =  Bao Miao , parent = Lao lao , level = 2 }
..................................................
{name =  Li Jing  , parent = Bao Miao , level = 3 }

How can we parse this with java? If there is a library with this functionality, let me know.

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3 answers

Make a model definition as shown below. Also put the class and parentName in the Model class.

class Employee{
    String name;
    String title;
    Employee children[];
    int level;
    String parentName;

    @Override
    public String toString(){
        return "{name =  "+name+" , parent = "+parentName+ ", level = "+level+ " }";
    }
}

Parse json data using the GSON API.

Employee e= new Gson().fromJson(new JsonReader(new FileReader("file.json")), Employee.class);

. , , . :)

import java.io.FileReader;

import com.google.gson.Gson;
import com.google.gson.stream.JsonReader;

public class ParseJson {

    public static void main(String a[]) {
        Gson g = new Gson();
        try {
            Employee e = g.fromJson(new JsonReader(new FileReader("file.json")), Employee.class);

            parseEmployees(e);
            printEmployee(e);
        } catch (Exception e1) {
            e1.printStackTrace();
        }

    }

    private static void parseEmployees(Employee e) {
        setParentAndLevel(e, 1, null);
    }

    private static void setParentAndLevel(Employee e, int lvl, String parent) {
        e.level = lvl;
        e.parentName = parent;
        if (e.children != null && e.children.length > 0) {
            lvl++;
            for (Employee emp : e.children) {
                setParentAndLevel(emp, lvl, e.name);
            }
        }
    }

    public static void printEmployee(Employee e){
        System.out.println(e);
        if (e.children != null && e.children.length > 0) {
            for (Employee emp : e.children) {
                printEmployee(emp);
            }
        }else{
            return ;
            }
        }
    }

    class Employee {
        String name;
        String title;
        Employee children[];
        int level;
        String parentName;

        @Override
        public String toString() {
            return "{name =  " + name + " , parent = " + parentName + ", level = " + level + " }";
        }
    }

:

{name =  Lao Lao , parent = null, level = 1 }
{name =  Bo Miao , parent = Lao Lao, level = 2 }
{name =  Li Jing , parent = Bo Miao, level = 3 }
{name =  Li Xin , parent = Bo Miao, level = 3 }
{name =  To To , parent = Li Xin, level = 4 }
{name =  Fei Fei , parent = Li Xin, level = 4 }
{name =  Xuan Xuan , parent = Li Xin, level = 4 }
{name =  Su Miao , parent = Lao Lao, level = 2 }
{name =  Pang Pang , parent = Su Miao, level = 3 }
{name =  Hei Hei , parent = Su Miao, level = 3 }
{name =  Xiang Xiang , parent = Hei Hei, level = 4 }
{name =  Dan Dan , parent = Hei Hei, level = 4 }
{name =  Zai Zai , parent = Hei Hei, level = 4 }
+1

, , , , jsonObject, bfs-, , , , , .

: , , - .

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.*;

public class Main {

    public static void main(String[] args) throws Exception{
        String JSON_STRING = "{\n" +
                "  \"name\": \"Lao Lao\",\n" +
                "  \"title\": \"general manager\",\n" +
                "  \"children\": [\n" +
                "    {\n" +
                "      \"name\": \"Bao Miao\",\n" +
                "      \"title\": \"department manager\",\n" +
                "      \"children\": [\n" +
                "        {\n" +
                "          \"name\": \"Li Jing\",\n" +
                "          \"title\": \"senior engineer\"\n" +
                "        },\n" +
                "        {\n" +
                "          \"name\": \"Li Xin\",\n" +
                "          \"title\": \"senior engineer\",\n" +
                "          \"children\": [\n" +
                "            {\n" +
                "              \"name\": \"To To\",\n" +
                "              \"title\": \"engineer\"\n" +
                "            },\n" +
                "            {\n" +
                "              \"name\": \"Fei Fei\",\n" +
                "              \"title\": \"engineer\"\n" +
                "            },\n" +
                "            {\n" +
                "              \"name\": \"Xuan Xuan\",\n" +
                "              \"title\": \"engineer\"\n" +
                "            }\n" +
                "          ]\n" +
                "        }\n" +
                "      ]\n" +
                "    },\n" +
                "    {\n" +
                "      \"name\": \"Su Miao\",\n" +
                "      \"title\": \"department manager\",\n" +
                "      \"children\": [\n" +
                "        {\n" +
                "          \"name\": \"Pang Pang\",\n" +
                "          \"title\": \"senior engineer\"\n" +
                "        },\n" +
                "        {\n" +
                "          \"name\": \"Hei Hei\",\n" +
                "          \"title\": \"senior engineer\",\n" +
                "          \"children\": [\n" +
                "            {\n" +
                "              \"name\": \"Xiang Xiang\",\n" +
                "              \"title\": \"UE engineer\"\n" +
                "            },\n" +
                "            {\n" +
                "              \"name\": \"Dan Dan\",\n" +
                "              \"title\": \"engineer\"\n" +
                "            },\n" +
                "            {\n" +
                "              \"name\": \"Zai Zai\",\n" +
                "              \"title\": \"engineer\"\n" +
                "            }\n" +
                "          ]\n" +
                "        }\n" +
                "      ]\n" +
                "    }\n" +
                "  ]\n" +
                "}] \n";

        JSONObject obj = new JSONObject(JSON_STRING);

        Deque<JSONObject> deque = new ArrayDeque<>();
        Map<String, String> res = new HashMap<>();
        int level = 1;
        res.put("NULL", obj.getString("name")+ "-" + level);
        deque.add(obj);
        Map<String, Integer> levelmap = new HashMap<>();
        levelmap.put(obj.getString("name"), 1);
        while (!deque.isEmpty()){
            JSONObject u = deque.poll();
            try {
                JSONArray children =  u.getJSONArray("children");
                for (int i = 0; i < children.length(); i++) {
                    deque.add(children.getJSONObject(i));
                    levelmap.put(children.getJSONObject(i).getString("name"), levelmap.get(u.getString("name")) + 1);
                    res.put(children.getJSONObject(i).getString("name"), u.getString("name") + "-" + levelmap.get(children.getJSONObject(i).getString("name")));
                }
            }catch (JSONException jex){
                System.out.println("end of the tree");
            }
        }

        //turn it back into a json array format
        String str = new String("[]");

        JSONArray jsonArray = new JSONArray(str);

        System.out.println(res);

        for(String key: res.keySet()){
            String st = new String("{}");
            JSONObject jsonObject = new JSONObject(st);
            //key is parent
            String[] tok = res.get(key).split("-");
            String child = tok[0];
            String mylevel = tok[1];
            jsonObject.put("name", key);
            jsonObject.put("level", mylevel);
            jsonObject.put("parent", child);
            jsonArray.put(jsonObject);
        }

        System.out.println(jsonArray.toString(2));

    }
}

:

[
  {
    "parent": "Hei Hei",
    "level": "4",
    "name": "Xiang Xiang"
  },
  {
    "parent": "Lao Lao",
    "level": "2",
    "name": "Bao Miao"
  },
  {
    "parent": "Lao Lao",
    "level": "1",
    "name": "NULL"
  },
  {
    "parent": "Su Miao",
    "level": "3",
    "name": "Hei Hei"
  },
  {
    "parent": "Hei Hei",
    "level": "4",
    "name": "Dan Dan"
  },
  {
    "parent": "Hei Hei",
    "level": "4",
    "name": "Zai Zai"
  },
  {
    "parent": "Li Xin",
    "level": "4",
    "name": "Xuan Xuan"
  },
  {
    "parent": "Su Miao",
    "level": "3",
    "name": "Pang Pang"
  },
  {
    "parent": "Li Xin",
    "level": "4",
    "name": "Fei Fei"
  },
  {
    "parent": "Li Xin",
    "level": "4",
    "name": "To To"
  },
  {
    "parent": "Bao Miao",
    "level": "3",
    "name": "Li Jing"
  },
  {
    "parent": "Lao Lao",
    "level": "2",
    "name": "Su Miao"
  },
  {
    "parent": "Bao Miao",
    "level": "3",
    "name": "Li Xin"
  }
]
+1

, . -, json POJO. , ,

class Employee{

String name;
String title;
List<Employee> Children;

}

If you can match this json with POJO. Then you just need to run the loop to get what you want.

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Source: https://habr.com/ru/post/1684011/

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