Sending and Parsing JSON Objects in Android [closed]

Question

I am surprised these have not been mentioned: but instead of using bare-bones rather manual process with json.org's little package, GSon and Jackson are much more convenient to use. So:

• GSON
• Jackson

So you can actually bind to your own POJOs, not some half-assed tree nodes or Lists and Maps. (and at least Jackson allows binding to such things too (perhaps GSON as well, not sure), JsonNode, Map, List, if you really want these instead of 'real' objects)

EDIT 19-MAR-2014:

Another new contender is Jackson jr library: it uses same fast Streaming parser/generator as Jackson (jackson-core), but data-binding part is tiny (50kB). Functionality is more limited (no annotations, just regular Java Beans), but performance-wise should be fast, and initialization (first-call) overhead very low as well. So it just might be good choice, especially for smaller apps.

You can use org.json.JSONObject and org.json.JSONTokener. you don't need any external libraries since these classes come with Android SDK

GSON is easiest to use and the way to go if the data have a definite structure.

Download gson.

Add it to the referenced libraries.

package com.tut.JSON;

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

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class SimpleJson extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        String jString = "{\"username\": \"tom\", \"message\": \"roger that\"}  ";


        GsonBuilder gsonb = new GsonBuilder();
        Gson gson = gsonb.create();
        Post pst;

        try {
            pst = gson.fromJson(jString,  Post.class);

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

Code for Post class

package com.tut.JSON;

public class Post {

    String message;
    String time;
    String username;
    Bitmap icon;
}

This is the JsonParser class

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }

Note: DefaultHttpClient is no longer supported by sdk 23, so it is advisable to use target sdk 21 with this code.

There's not really anything to JSON. Curly brackets are for "objects" (associative arrays) and square brackets are for arrays without keys (numerically indexed). As far as working with it in Android, there are ready made classes for that included in the sdk (no download required).

Check out these classes: http://developer.android.com/reference/org/json/package-summary.html

Other answers have noted Jackson and GSON - the popular add-on JSON libraries for Android, and json.org, the bare-bones JSON package that is included in Android.

But I think it is also worth noting that Android now has its own full featured JSON API.

This was added in Honeycomb: API level 11.

This comprises
- android.util.JsonReader: docs, and source
- android.util.JsonWriter: docs, and source

I will also add one additional consideration that pushes me back towards Jackson and GSON: I have found it useful to use 3rd party libraries rather then android.* packages because then the code I write can be shared between client and server. This is particularly relevant for something like JSON, where you might want to serialize data to JSON on one end for sending to the other end. For use cases like that, if you use Java on both ends it helps to avoid introducing android.* dependencies.

Or I guess one could grab the relevant android.* source code and add it to your server project, but I haven't tried that...

You can download a library from http://json.org (Json-lib or org.json) and use it to parse/generate the JSON