Unable to parse the key and value of nested json file using java

Question

Below is the json file i am trying to parse.I want to print all key and corresponding values.

{
 "A":{
   "name":"Ram",
   "gender":"male",
   "designation":"engineer"
 },
 "B":{
  "name":"Shyam",
  "gender":"male",
  "designation":"student"
 },
 "C":{
  "name":"Mohan",
  "gender":"male",
  "designation":"manager"
 }
}

I have tried the following code:

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Iterator;
import org.json.JSONArray;
import org.json.JSONObject;
import org.json.simple.parser.JSONParser;

public class FetchJsonNested {
    public static void main(String args[]) throws FileNotFoundException {
        try {
            JSONParser jp=new JSONParser();
            Object obj=jp.parse(new FileReader("C:\\Users\\DELL\\Documents\\NetBeansProjects\\WaterNetwork\\web\\kusharray.json"));
            JSONObject job=(JSONObject)obj;
            Iterator < ? > keys = job.keys();

            while (keys.hasNext()) {
                String key = (String) keys.next();
                System.out.println(key);
                if (job.get(key) instanceof JSONObject) {
                    System.out.println(job.get(key));
                }
            }
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
}

I have read stuffs from many site but no one is working like the way i want.I want to print all keys and corresponding values.

java.lang.ClassCastException: org.json.simple.JSONArray cannot be cast to org.json.JSONObject — Kushagra Sinha
– Kushagra Sinha, Commented Jun 22, 2017 at 7:36
I just want to print the key(For example "A") and after that using the nested key to get corresponding value.something like this name="Ram" — Kushagra Sinha
– Kushagra Sinha, Commented Jun 22, 2017 at 7:42
You're supposed to ask questions, "suggest me a working code" is asking someone to code it for you. — James Z
– James Z, Commented Jun 22, 2017 at 7:51

Asew · Accepted Answer · 2018-02-28 21:37:15Z

1

Using org.json as you did in your example :

String jsonStr = "{\"A\":{\"name\":\"Ram\",\"gender\":\"male\",\"designation\":\"engineer\"},\"B\":{\"name\":\"Shyam\",\"gender\":\"male\",\"designation\":\"student\"},\"C\":{\"name\":\"Mohan\",\"gender\":\"male\",\"designation\":\"manager\"}}";
JSONObject json = new JSONObject(jsonStr);

for (Object key : json.keySet().toArray()){
    JSONObject data = json.getJSONObject(key.toString());
    System.out.println("json :" + data.toString());
    System.out.println("name :" +data.getString("name"));
    System.out.println("gender :" +data.getString("gender"));
    System.out.println("designation :" +data.getString("designation"));
}

Now you can replace my first line "String jsonStr = ..." with your file reader.

edited Feb 28, 2018 at 21:37

user8280225

answered Jun 22, 2017 at 9:23

Asew

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Comments

Marcelo Idemax · Accepted Answer · 2017-06-22 09:07:11Z

0

below follow not the awesome and most elegant solution but this can lead you to what you need.

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

public class Main {

    public static void main(String[] args) throws Exception {
        String jsonString = loadJSONFile();

        JsonElement jsonElement = new JsonParser().parse(jsonString);
        JsonObject jsonObject = jsonElement.getAsJsonObject();

        print(jsonObject);
    }

    private static String loadJSONFile() throws FileNotFoundException {
        Scanner scanner = new Scanner(new FileReader("path/to/the/json/file.ext"));
        StringBuilder stringBuilder = new StringBuilder();

        while (scanner.hasNext()) {
            stringBuilder.append(scanner.next());
        }

        scanner.close();

        return stringBuilder.toString();
    }

    private static void print(JsonObject jsonObject) {
        Set<Map.Entry<String, JsonElement>> entries = jsonObject.entrySet();

        for (Map.Entry<String, JsonElement> entry : entries) {
            System.out.println(entry.getKey() + ": " + entry.getValue());

            try {
                JsonElement jsonElement = new JsonParser().parse(String.valueOf(entry.getValue()));
                JsonObject innerJsonObject = jsonElement.getAsJsonObject();

                print(innerJsonObject);
            } catch (Exception e) {
                // is not a JSON
            }
        }
    }
}

Output example:

A: {"name":"Ram","gender":"male","designation":"engineer"}
name: "Ram"
gender: "male"
designation: "engineer"
B: {"name":"Shyam","gender":"male","designation":"student"}
name: "Shyam"
gender: "male"
designation: "student"
C: {"name":"Mohan","gender":"male","designation":"manager"}
name: "Mohan"
gender: "male"
designation: "manager"

edited Jun 22, 2017 at 9:07

answered Jun 22, 2017 at 8:10

Marcelo Idemax

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2 Comments

Kushagra Sinha Over a year ago

thanks a lot.But sir the json file is dynamic.so how can I convert json file to string all the time it get updated.

Kushagra Sinha Over a year ago

thnxx a lot sir.

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