This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Notice that you have asked two questions. This is the XML forum, so let me answer the XML question. You take the InputStream which your servlet gets from the POST data, and pass it to your Stax parser. If I read the documentation correctly, that would be something like