Android OAuth2 Resource Owner Password Credentials Grant

Question

The app needs to connect to a API that only support OAuth2 Resource Owner Password Credentials Grant. I tryed using the code bellow, but get the response code 400 "bad request". Using the same code I can connect to a normal site and retrive the content.

I know that the API code is working because using Postman works. In Postman I just make a post request, suppling the username, password, and grant_type, and using x-www-form-urlencoded

The return of the connection is a json.

Any ideas what it's wrong? Should I use a 3rd party library? Any recomendations? Thanks.

In the code I changed the credentials and the API link

public class GetData extends AsyncTask<String, String, String> {

@Override
public String doInBackground(String... args) {

    URL url;
    HttpURLConnection urlConnection = null;
    try {
        url = new URL("http://someaddress.azurewebsites.net/api/token");
        urlConnection = (HttpURLConnection) url.openConnection();
        urlConnection.setRequestMethod("POST");
        urlConnection.setRequestProperty("username", "some@email.com");
        urlConnection.setRequestProperty("password", "123");
        urlConnection.setRequestProperty("grant_type", "password");

        urlConnection.connect();

        int responseCode = urlConnection.getResponseCode();
        String responseMsg = urlConnection.getResponseMessage();
        if (responseCode >= 400 && responseCode <= 499) {
            throw new Exception(responseMsg + " :: " + responseCode);
        }

        InputStream in = urlConnection.getInputStream();
        InputStreamReader isw = new InputStreamReader(in);

        int data = isw.read();
        while (data != -1) {
            char current = (char) data;
            data = isw.read();
            System.out.print(current);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (urlConnection != null) {
            urlConnection.disconnect();
        }
    }
    return null;
}

@Override
protected void onPostExecute(String result) {

    //Do something with the JSON string

}
}

---

Adding some log, as sugested by Amod. This is the return of the printStackTrace in the code above.

12-12 01:16:33.210 8558-8643/com.marcussabino.tsftestedeconexo W/System.err: java.lang.Exception: Bad Request :: 400
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at com.marcussabino.tsftestedeconexo.GetData$override.doInBackground(GetData.java:40)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at com.marcussabino.tsftestedeconexo.GetData$override.access$dispatch(GetData.java)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at com.marcussabino.tsftestedeconexo.GetData.doInBackground(GetData.java:0)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at com.marcussabino.tsftestedeconexo.GetData.doInBackground(GetData.java:15)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:295)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
12-12 01:16:33.211 8558-8643/com.marcussabino.tsftestedeconexo W/System.err:     at java.lang.Thread.run(Thread.java:818)

Answer 1

I was understanding setRequestPorperty wrong!!

Thanks Nell and Stunner: https://stackoverflow.com/a/40576153/4276115

Here is the code that worked for me:

public class GetData extends AsyncTask<String, String, String> {

@Override
public String doInBackground(String... args) {
    String urlParameters  = "username=" + args[0] +
            "&password=" + args[1] +
            "&grant_type=" + args[2];

    byte[] postData = urlParameters.getBytes( StandardCharsets.UTF_8 );
    int postDataLength = postData.length;

    URL url;
    HttpURLConnection urlConnection = null;
    try {
        url = new URL("http://somesite.azurewebsites.net/api/token");
        urlConnection = (HttpURLConnection) url.openConnection();
        urlConnection.setDoOutput(true);
        urlConnection.setDoInput(true);
        urlConnection.setRequestMethod("POST");
        urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        urlConnection.setRequestProperty("charset", "utf-8");
        urlConnection.setRequestProperty("Content-Length", Integer.toString(postDataLength));
        urlConnection.setUseCaches(false);

        try(DataOutputStream wr = new DataOutputStream(urlConnection.getOutputStream())) {
            wr.write( postData );
        }

        int responseCode = urlConnection.getResponseCode();
        String responseMsg = urlConnection.getResponseMessage();
        if (responseCode >= 400 && responseCode <= 499) {
            throw new Exception(responseMsg + " :: " + responseCode);
        }

        InputStream in = urlConnection.getInputStream();

        BufferedReader  reader = new BufferedReader(new InputStreamReader(in));

        StringBuffer buffer = new StringBuffer();
        String line = "";

        while ((line = reader.readLine()) != null) {
            buffer.append(line+"\n");
            Log.v("JSON", "> " + line);   //here you get the response

        }

    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (urlConnection != null) {
            urlConnection.disconnect();
        }
    }
    return null;
}

@Override
protected void onPostExecute(String result) {

    //Do something with the JSON string

}
}