Retrieving values from nested JSON Object

Question

I've got JSON file, which I want to parse. The JSON file ("myfile") has format as follows:

{
    "LanguageLevels": {
        "1": "Początkujący",
        "2": "ŚrednioZaawansowany",
        "3": "Zaawansowany",
        "4": "Ekspert"
    }
}

I want to retrieve value (ŚrednioZaawansowany) of Key 2 from Language Levels.

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

public class JsonSimpleExample {
public static void main(String[] args) {

JSONParser parser = new JSONParser();

try {

    Object obj = parser.parse(new FileReader("myfile"); 
    JSONObject jsonObject = (JSONObject) obj;
    JSONObject jsonChildObject = (JSONObject)jsonObject.get("LanguageLevels");

What to do next? How I can iterate over it?

I suggest to read the official documentation and take a look at their examples if there are some. — Njol
– Njol, Commented Jan 3, 2014 at 8:58

Xiao Liang · Accepted Answer · 2018-09-12 21:48:09Z

36

Maybe you're not using the latest version of a JSON for Java Library.

json-simple has not been updated for a long time, while JSON-Java was updated 2 month ago.

JSON-Java can be found on GitHub, here is the link to its repo: https://github.com/douglascrockford/JSON-java

After switching the library, you can refer to my sample code down below:

public static void main(String[] args) {
    String JSON = "{\"LanguageLevels\":{\"1\":\"Pocz\\u0105tkuj\\u0105cy\",\"2\":\"\\u015arednioZaawansowany\",\"3\":\"Zaawansowany\",\"4\":\"Ekspert\"}}\n";

    JSONObject jsonObject = new JSONObject(JSON);
    JSONObject getSth = jsonObject.getJSONObject("LanguageLevels");
    Object level = getSth.get("2");

    System.out.println(level);
}

And as JSON-Java open-sourced, you can read the code and its document, they will guide you through.

Hope that it helps.

edited Sep 12, 2018 at 21:48

answered Jan 3, 2014 at 9:08

Xiao Liang

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5 Comments

m.aibin Over a year ago

In constructor of jsonObject Eclipse prints this error: The constructor JSONObject(String) is undefined

Xiao Liang Over a year ago

@m.aibin Please note that all the files you downloaded from GitHub are not placed in the right package. You must create a new package called org.json then, drap'n'drop all the java files to that package. And you rock!

Xiao Liang Over a year ago

@m.aibin Also, plz note that, it's not a nested JSON Array, but a nested JSON object. You better change this question's title, it could be misleading.

m.aibin Over a year ago

yes, I used wrong package :) One more question - is it available to get this package from GitHub as a Maven Dependency?? Now I've got it as a package to compile with other my classes

Xiao Liang Over a year ago

Check this out: mvnrepository.com/artifact/org.json/json. My network speed of linking maven sites is extremely low, so cannot give it a try. But this should be right for your need! ;-)

preetesh gurjar · Accepted Answer · 2017-04-18 11:23:05Z

You will have to iterate step by step into nested JSON.

for e.g a JSON received from Google geocoding api

{
   "results" : [
      {
         "address_components" : [
            {
               "long_name" : "Bhopal",
               "short_name" : "Bhopal",
               "types" : [ "locality", "political" ]
            },
            {
               "long_name" : "Bhopal",
               "short_name" : "Bhopal",
               "types" : [ "administrative_area_level_2", "political" ]
            },
            {
               "long_name" : "Madhya Pradesh",
               "short_name" : "MP",
               "types" : [ "administrative_area_level_1", "political" ]
            },
            {
               "long_name" : "India",
               "short_name" : "IN",
               "types" : [ "country", "political" ]
            }
         ],
         "formatted_address" : "Bhopal, Madhya Pradesh, India",
         "geometry" : {
            "bounds" : {
               "northeast" : {
                  "lat" : 23.3326697,
                  "lng" : 77.5748062
               },
               "southwest" : {
                  "lat" : 23.0661497,
                  "lng" : 77.2369767
               }
            },
            "location" : {
               "lat" : 23.2599333,
               "lng" : 77.412615
            },
            "location_type" : "APPROXIMATE",
            "viewport" : {
               "northeast" : {
                  "lat" : 23.3326697,
                  "lng" : 77.5748062
               },
               "southwest" : {
                  "lat" : 23.0661497,
                  "lng" : 77.2369767
               }
            }
         },
         "place_id" : "ChIJvY_Wj49CfDkR-NRy1RZXFQI",
         "types" : [ "locality", "political" ]
      }
   ],
   "status" : "OK"
}

I shall iterate in below given fashion to "location" : { "lat" : 23.2599333, "lng" : 77.412615

//recieve JSON in json object

        JSONObject json = new JSONObject(output.toString());
        JSONArray result = json.getJSONArray("results");
        JSONObject result1 = result.getJSONObject(0);
        JSONObject geometry = result1.getJSONObject("geometry");
        JSONObject locat = geometry.getJSONObject("location");

        //"iterate onto level of location";

        double lat = locat.getDouble("lat");
        double lng = locat.getDouble("lng");

Jakub Kotowski · Accepted Answer · 2014-01-03 08:59:29Z

7

You can see that JSONObject extends a HashMap, so you can simply use it as a HashMap:

JSONObject jsonChildObject = (JSONObject)jsonObject.get("LanguageLevels");
for (Map.Entry in jsonChildOBject.entrySet()) {
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}

answered Jan 3, 2014 at 8:59

Jakub Kotowski

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Comments

dehlen · Accepted Answer · 2014-01-03 08:59:07Z

2

JSONArray jsonChildArray = (JSONArray) jsonChildArray.get("LanguageLevels");
    JSONObject secObject = (JSONObject) jsonChildArray.get(1);

I think this should work, but i do not have the possibility to test it at the moment..

answered Jan 3, 2014 at 8:59

dehlen

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1 Comment

Xiao Liang Over a year ago

Note that LanguageLevels is not a JSON Array! Because it starts with a brace, not an open bracket. So your code here may not be appropriate.

eabyshev · Accepted Answer · 2014-09-30 18:26:59Z

1

To see all keys of Jsonobject use this

    String JSON = "{\"LanguageLevels\":{\"1\":\"Pocz\\u0105tkuj\\u0105cy\",\"2\":\"\\u015arednioZaawansowany\",\"3\":\"Zaawansowany\",\"4\":\"Ekspert\"}}\n";
    JSONObject obj = new JSONObject(JSON);
    Iterator iterator = obj.keys();
    String key = null;
    while (iterator.hasNext()) {
        key = (String) iterator.next();
        System.out.pritnln(key);
    }

answered Sep 30, 2014 at 18:26

eabyshev

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Comments

Braj Thakur · Accepted Answer · 2020-07-11 15:27:15Z

Try this, you can parse nested JSON

public static String getJsonValue(String jsonReq, String key) {
        JSONObject json = new JSONObject(jsonReq);
        boolean exists = json.has(key);
        Iterator<?> keys;
        String nextKeys;
        String val = "";
        if (!exists) {
            keys = json.keys();
            while (keys.hasNext()) {
                nextKeys = (String) keys.next();
                try {
                    if (json.get(nextKeys) instanceof JSONObject) {
                        return getJsonValue(json.getJSONObject(nextKeys).toString(), key);
                    } else if (json.get(nextKeys) instanceof JSONArray) {
                        JSONArray jsonArray = json.getJSONArray(nextKeys);
                        int i = 0;
                        if (i < jsonArray.length()) do {
                            String jsonArrayString = jsonArray.get(i).toString();
                            JSONObject innerJson = new JSONObject(jsonArrayString);
                            return getJsonValue(innerJson.toString(),key);
                        } while (i < jsonArray.length());
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        } else {
            val = json.get(key).toString();
        }
        return val;
    }

Soropromo · Accepted Answer · 2022-10-24 11:46:29Z

Here is an example of retrieving nested JSON object. Department and Product are model classes. Department class holds department as a String and products as ArrayList of Product Product class holds name as a String

depts and products are ArrayList of corresponding model classes

        String jsonDataString = readJSONDataFromFile();
        JSONArray jsonArray = new JSONArray(jsonDataString);

        for (int i=0; i<jsonArray.length(); ++i) {

            JSONObject departmentJSONObject = jsonArray.getJSONObject(i);

            String deptName = departmentJSONObject.getString("department");
            JSONArray productsJSONArray =  departmentJSONObject.getJSONArray("products");

            for (int j =0; j <productsJSONArray.length();j++){
                JSONObject productJSONObject = productsJSONArray.getJSONObject(j);
               String prodName = productJSONObject.getString("name");

                Product product = new Product(prodName);
                products.add(product);
            }
            Department department = new Department(deptName, products);
            depts.add(department);

Here is my raw json file

 [
  {
    "department": "Cold Drink",
    "products": [
      {
        "name": "lemonade",
        "img": "some_url"
      },
      {
        "name": "Oj",
        "img": "some_url"
      }
    ]
  },
  {
    "department": "CD2",
    "products": [
      {
        "name": "lemonade2",
        "img": "some_url2"
      },
      {
        "name": "oj2",
        "img": "some_url2"
      }
    ]
  },
  {
    "department": "CD3",
    "products": [
      {
        "name": "lemonade3",
        "img": "some_url3"
      },
      {
        "name": "oj3",
        "img": "some_url3"
      }
    ]
  }
]

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