Apps JSON response from server different than expected

[Bogdan Tudorascu]

I'm trying to create a login application on android and I get an error telling me that the JSON object is null.

I get the error from here :

 public JSONObject loginUser(String email, String password){
            // Building Parameters
            List<NameValuePair> params = new ArrayList<>();
            params.add(new BasicNameValuePair("tag", login_tag));
            params.add(new BasicNameValuePair("email", email));
            params.add(new BasicNameValuePair("password", password));
            JSONObject json = jsonParser.getJSONFromUrl(loginURL, params);
            if (json == null) {
                Log.e("JSON", "Object is null!!!");
            }
            return json;
        }

This is my JSONParser:

    public class JSONParser {
        static InputStream is = null;
        static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    private String convertStreamToString(InputStream is) throws Exception {
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line);
        }
        is.close();
        return sb.toString();
    }

    public JSONObject getJSONFromUrl(String url, List params) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            for (int i=0; i<params.size(); i++) {
                Log.v("askj",params.get(i).toString());
            }
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            try {
                Log.v("askj","HTTP Entity : " + convertStreamToString(httpPost.getEntity().getContent()));
            }catch (Exception e){
                e.printStackTrace();
            }

            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();
            Log.v("askj",json);
            Log.e("JSON", json);
        } 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;

    }
}

And this is my index.php :

<?php echo json_encode($_POST); exit;?>

This is what I'm sending and receiving:

   05-14 10:49:26.547  27963-28074/name.company.project V/askj﹕ tag=login
    05-14 10:49:26.547  27963-28074/name.company.project V/askj﹕ email=emailTest
    05-14 10:49:26.547  27963-28074/name.company.project V/askj﹕ password=passTest
    05-14 10:49:26.557  27963-28074/name.company.project V/askj﹕ HTTP Entity sent : tag=login&email=emailTest&password=passTest
    05-14 10:49:27.117  27963-28074/name.company.project V/askj﹕ json received: []

The website works because I tested it with Postman, so the problem is within the JSONParser.