Service - Gửi dữ liệu Post lên api

public class POSTActivity extends AppCompatActivity implements View.OnClickListener {

TextView tvIsConnected;
Button btnPost;
String TAG = "json";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login_activity_second);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    btnPost.setOnClickListener(this);
}

@Override
public void onClick(View view) {

    switch(view.getId()) {
        case R.id.btnPost:
            if (!validate())
                 new HttpAsyncTask().execute("http://zhaksy-adam.kz/api/Requisitions/PostRequisition");
                 break;
    }

}

    private class HttpAsyncTask extends AsyncTask<String, String, String> {
    @Override
    protected String doInBackground(String... urls) {
        return POST(urls[0]);
    }

public static String POST(String url){
    InputStream inputStream = null;
    String result = "";
    try {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);

        String json = "";
        JSONObject jsonObject = new JSONObject();


         jsonObject.add("CityID", "1");
         jsonObject.add("TypeID","1");
         jsonObject.add("Title", "SomeTitle");
         jsonObject.add("RegionID", "1");
         jsonObject.add("Phone1", "+7(705)105-78-70");
         jsonObject.add("Decription","<p>Some Description</p>");
         jsonObject.add("Date", "29-02-2016");


         json = jsonObject.toString();
        StringEntity se = new StringEntity(json);
        httpPost.setEntity(se);

        httpPost.setHeader("accept", "json");
        httpPost.setHeader("Content-type", "json");

        HttpResponse httpResponse = httpclient.execute(httpPost);

        inputStream = httpResponse.getEntity().getContent();

        // convert inputstream to string
        if(inputStream != null)
        { result = convertInputStreamToString(inputStream);
             Log.d("json","inputStream result"+result);}
        else
            result = "Did not work!";
            Log.d("json","result"+result);

    } catch (Exception e) {
        Log.d("json","e.getLocalizedMessage()"+ e.getLocalizedMessage());
    }

    //  return result
    return result;
}

    // onPostExecute displays the results of the AsyncTask.
    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(getBaseContext(), "Data Sent!", Toast.LENGTH_LONG).show();
    }
}

private static String convertInputStreamToString(InputStream inputStream) throws IOException {
    BufferedReader bufferedReader = new BufferedReader( new InputStreamReader(inputStream));
    String line = "";
    String result = "";
    while((line = bufferedReader.readLine()) != null)
        result += line;

    inputStream.close();
    return result;

}