How to POST XML (org.w3c.dom.Document) and String (timestamp) on Android?

Question

I'm working on a software-project for University, where we have to implement the client to a specific REST-service on Android. The REST-Post accepts two params:

• document (a XML document, in my code existing as a org.w3c.dom.Document created from a "TriageTag"-Object)
• timestamp (a string, representing the client's POST-time)

What I have so far:

            [... timestamp / post url preparations etc. ...]

            //Generate String from XML
            InputSource is = new InputSource(c.getResources().openRawResource(R.raw.cda_template));
            Document doc = CDAParser.TriageTagObjectToXml(tag, is);

            //Data
            List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>

            //FILL IN: SET DOC AS PARAM. WHO DO I DO THIS!?!?

            nameValuePairs.add(new BasicNameValuePair("timestamp", timestamp));
            httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

            // Execute HTTP Post Request
            HttpResponse response = client.execute(httppost);
            StatusLine status = response.getStatusLine();

            [... check status etc. ... ]