Signing HttpUrlConnection using OkHttpClient and Retrofit

gistfile1.txt

   @Override
    public Response execute(Request request) throws IOException {
        HttpsURLConnection connection = (HttpsURLConnection) super.openConnection(request);
        try {
            prepareRequest(connection, request);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return readResponse(connection);
    }

    void prepareRequest(HttpURLConnection connection, Request request)
            throws IOException, OAuthExpectationFailedException, NoSuchAlgorithmException,
            OAuthCommunicationException, OAuthMessageSignerException {
        if (Build.VERSION.SDK_INT > 13) {
            connection.setRequestProperty("Connection", "close");
        }
        connection.setRequestMethod(request.getMethod());
        connection.setDoInput(true);
        for (Header header : request.getHeaders()) {
            connection.addRequestProperty(header.getName(), header.getValue());
        }
        TypedOutput body = request.getBody();
        long length = -1;
        if (body != null) {
            connection.setDoOutput(true);
            length = body.length();
        }
        RequestSigner.create(CONSUMER_KEY, CONSUMER_SECRET)
                .setOAuthTokenAndSecret(getToken(request), getoAuthSecret(request))
                .sign(request, connection);
        if (length != -1) {
            connection.setFixedLengthStreamingMode((int) length);
        } else {
            connection.setChunkedStreamingMode(CHUNK_SIZE);
        }
        if (body!=null) {
            body.writeTo( connection.getOutputStream() );
        }
    }