How to get 401 response without handling it using try/catch in android

Question

I am using HttpUrlConnection to make network requests from my android application. Everything works fine except one thing, 401. Whenever the server returns response with status code 401, my app throws IOException with a message stating, "no authentication challenge found". After googling it, I haven't found a single solution, but only workaround (handling it using try/catch, assuming its a 401 response).

here is the code snippet:

public Bundle request(String action, Bundle params, String cookie) throws FileNotFoundException, MalformedURLException, SocketTimeoutException,
        IOException {

    OutputStream os;

    String url = baseUrl + action;
    Log.d(TAG, url);
    HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
    conn.setConnectTimeout(30 * 1000);
    conn.setReadTimeout(30 * 1000);
    conn.setRequestProperty("User-Agent", System.getProperties().getProperty("http.agent") + "AndroidNative");
    conn.setRequestMethod("POST");
    conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
    conn.setRequestProperty("Connection", "Keep-Alive");
    conn.setDoOutput(true);
    conn.setDoInput(true);
    if (cookie != null) {
        conn.setRequestProperty("Cookie", cookie);
    }

    if (params != null) {
        os = conn.getOutputStream();
        os.write(("--" + boundary + endLine).getBytes());
        os.write((encodePostBody(params, boundary)).getBytes());
        os.write((endLine + "--" + boundary + endLine).getBytes());
        uploadFile(params, os);
        os.flush();
        os.close();
    }

    conn.connect();

    Bundle response = new Bundle();
    try {
        response.putInt("response_code", conn.getResponseCode());
        Log.d(TAG, conn.getResponseCode() + "");
        response.putString("json_response", read(conn.getInputStream()));
        List<String> responseCookie = conn.getHeaderFields().get("set-cookie");
        // Log.d(TAG, responseCookie.get(responseCookie.size() - 1));
        response.putString("cookie", responseCookie.get(responseCookie.size() - 1));
    } catch (SocketTimeoutException e) {
        throw new SocketTimeoutException(e.getLocalizedMessage());
    } catch (FileNotFoundException e) {
        throw new FileNotFoundException(e.getLocalizedMessage());
    } catch (IOException e) {
        e.printStackTrace();
        response.putInt("response_code", HttpURLConnection.HTTP_UNAUTHORIZED);
        response.putString("json_response", read(conn.getErrorStream()));
    }

    // debug
    Map<String, List<String>> map = conn.getHeaderFields();
    for (String key : map.keySet()) {
        List<String> values = map.get(key);
        for (String value : values) {
            Log.d(key, value);
        }
    }

    conn.disconnect();

    return response;
}

I really want to know, why this exception is thrown? What does authentication challenge mean? How to provide authentication challenge? what change I have to make in my code to overcome this situation?

Please enlighten me.. :)

Answer 1

IOException is quite a general exception, and you cannot safely assume a 401 status code every time it's thrown.

If the first time you request the status code it happens to contain a 401, HttpURLConnection will throw an IOException. At this point, the internal status of the connection will have changed, and it will now be able to give you the status code, without any error.

int status = 0;
try {
    status = conn.getResponseCode();
} catch (IOException e) {
    // HttpUrlConnection will throw an IOException if any 4XX
    // response is sent. If we request the status again, this
    // time the internal status will be properly set, and we'll be
    // able to retrieve it.
    status = conn.getResponseCode();
}
if (status == 401) {
    // ...
}

For more details, http://www.tbray.org/ongoing/When/201x/2012/01/17/HttpURLConnection