Android HttpsURLConnection - simple POST request with parameters

Question

I've been trying to get a simple android client server app working, and I've had nothing but trouble. I'm hoping someone can look at this code and see what I'm doing wrong, maybe I'm doing things in the wrong order, or forgetting something? Just adding the relevant parts

            HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
            conn.addRequestProperty("Content-Type", "application/json");

            // set some made up parameters
            String str =  "{'login':'superman@super.com','password':'password'}";
            byte[] outputInBytes = str.getBytes("UTF-8");
            OutputStream os = conn.getOutputStream();
            os.write( outputInBytes );
            os.close();

            // connection.setDoOutput(true); //should trigger POST - move above -> crash
            conn.setRequestMethod("POST");  // explicitly set POST -move above so we can set params -> crash
            conn.setDoInput(true);

The error I get is

'exception: java.net.ProtocolException: method does not support a request body: GET'

If I just do a POST request without parameters it's fine, so I guess I should move the connection.setDoOutput(true); or conn.setRequestMethod("POST"); higher up, that should work right? When I do that I get the error:

exception: java.net.ProtocolException: Connection already established.

So, if I try to set to POST before adding parameters it doesn't work, if I try to do it after it doesn't work... what am I missing? Is there another way I should be doing this? Am I adding parameters incorrectly? I've been searching for a simple android networking example, and I can't find any, is there any example the official Android site? All I want to do is a very basic network operation, this is so frustrating!

EDIT: I need to use HttpsURLConnection for reasons not included in the above code- I need to authenticate, trust hosts, etc- so I'm really looking for a potential fix for the above code if possible.

Answer 1

I followed this tutorial on making http calls:

http://www.androidhive.info/2012/01/android-json-parsing-tutorial/

Works fine with no problems.

Below is a class that I have modified from the sample (timeout code based on this answer by kuester2000):

public class ServiceHandler {

    static String response = null;
    public final static int GET = 1;
    public final static int POST = 2;
    String TAG = ((Object) this).getClass().getSimpleName();

    public ServiceHandler() {

    }

    /**
     * Making service call
     *
     * @url - url to make request
     * @method - http request method
     */
    public String makeServiceCall(String url, int method) {
        return this.makeServiceCall(url, method, null);
    }

    /**
     * Making service call
     *
     * @url - url to make request
     * @method - http request method
     * @params - http request params
     */
    public String makeServiceCall(String url, int method,
                                  List<NameValuePair> params) {
        try {
            // http client
            HttpParams httpParameters = new BasicHttpParams();
            // Set the timeout in milliseconds until a connection is established.
            // The default value is zero, that means the timeout is not used.
            int timeoutConnection = 2000;
            HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
            // Set the default socket timeout (SO_TIMEOUT)
            // in milliseconds which is the timeout for waiting for data.
            int timeoutSocket = 2000;
            HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);

            DefaultHttpClient httpClient = new DefaultHttpClient(httpParameters);
            HttpEntity httpEntity = null;
            HttpResponse httpResponse = null;

            // Checking http request method type
            if (method == POST) {
                HttpPost httpPost = new HttpPost(url);
                // adding post params
                if (params != null) {
                    httpPost.setEntity(new UrlEncodedFormEntity(params));
                }

                httpResponse = httpClient.execute(httpPost);

            } else if (method == GET) {
                // appending params to url
                if (params != null) {
                    String paramString = URLEncodedUtils
                            .format(params, "utf-8");
                    url += "?" + paramString;
                }
                Log.e("Request: ", "> " + url);
                HttpGet httpGet = new HttpGet(url);

                httpResponse = httpClient.execute(httpGet);

            }
            if (httpResponse != null) {
                httpEntity = httpResponse.getEntity();
            } else {
                Log.e(TAG, "httpResponse is null");
            }
            response = EntityUtils.toString(httpEntity);

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

        return response;

    }
}

And this is how I use the class:

nameValuePairs = new ArrayList<NameValuePair>();
String param_value = "value";
String param_name = "name";
nameValuePairs.add(new BasicNameValuePair(param_name, param_value));

// Creating service handler class instance
sh = new ServiceHandler();

String json = sh.makeServiceCall(Utils.getUrl, ServiceHandler.GET, nameValuePairs);

Answer 2

Here is an example of how to post with a JSON Object:

JSONObject payload=new JSONObject();
        try {
            payload.put("password", params[1]);
            payload.put("userName", params[0]);
        } catch (JSONException e) {
            e.printStackTrace();
        }
        String responseString="";
        try 
        {
            HttpPost httpPost = new HttpPost("www.theUrlYouQWant.com");

            httpPost.setEntity(new StringEntity(payload.toString()));
            httpPost.setHeader("Accept", "application/json");
            httpPost.setHeader("Content-type", "application/json");
            HttpResponse response = new DefaultHttpClient().execute(httpPost);
            responseString = EntityUtils.toString(response.getEntity());
        } 
        catch (ClientProtocolException e) 
        {
            e.printStackTrace();
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }

And example of how to get

String responseString = "";
        //check if the username exists
        StringBuilder builder = new StringBuilder();
        HttpClient client = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet("www.theUrlYouQWant.com");
        ArrayList<String> existingUserName = new ArrayList<String>();
        try 
        {
              HttpResponse response = client.execute(httpGet);
              StatusLine statusLine = response.getStatusLine();
              int statusCode = statusLine.getStatusCode();
              if (statusCode == 200) {
                HttpEntity entity = response.getEntity();
                InputStream content = entity.getContent();
                BufferedReader reader = new BufferedReader(new InputStreamReader(content));
                String line;
                while ((line = reader.readLine()) != null) {
                  builder.append(line);
                }
              } 
              else 
              {
                Log.e(ParseException.class.toString(), "Failed to download file");
              }
        } 
        catch (ClientProtocolException e) 
        {
            e.printStackTrace();
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }