XML, jdom og servlets?

Hej

jeg har skrevet et stykke kode som skulle tage alle vores jokes i en given kategori og skrive ud i xml form... hvorfor skriver den et tomt xml dokument ud som i kan se på linket...?

Kode:
  response.setContentType("text/html");
      //PrintWriter out = response.getWriter();
      String x = request.getParameter("category");
      Document document = new SAXBuilder().build(new File("/home/cleo1/u031407/dWebTek/jokeml.xml"));
      Namespace ns = Namespace.getNamespace("jml","http://www.brics.dk/dWebTek/JokeML");
      SortedSet jokes = Collections.synchronizedSortedSet(new TreeSet());
      List children = document.getRootElement().getChildren("joke");
      Iterator iter = children.iterator();   
      Element root = new Element("collection",ns);
            while (iter.hasNext()) {
              Element e = new Element("category", root.getNamespace());
              Element joke = (Element) iter.next();
              String s = joke.getAttributeValue("category");
                  if (s.equals(x)) {
                e.addContent(s);
                root.addContent(e);
              }
            }
            Document d = new Document(root);
              new XMLOutputter().output(d, response.getOutputStream());

Link:
http://dwebtek.daimi.au.dk:8080/u031407/JokeServer/Retrieve?category=animals

XML dokument som den henter fra:
<?xml version="1.0" encoding="iso-8859-1"?>
<jml:collection xmlns:jml="http://www.brics.dk/dWebTek/JokeML">
  <jml:joke id="u655632gs6" category="animals">
    <jml:title>Two Cows in a Field</jml:title>
    <jml:date>11022004</jml:date>
    <jml:setup>
      Two cows are standing in a field eating grass. The first cow says: "Moooo"!
    </jml:setup>
    <jml:punchline>
      The second cow replies: "Hey, I was just gonna say that"!
    </jml:punchline>
  </jml:joke>

<jml:joke id="u655632gs7" category="århus joke">
    <jml:title>Two Cows in a Field</jml:title>
    <jml:date>11022004</jml:date>
    <jml:setup>
      Two cows are standing in a field eating grass. The first cow says: "Moooo"!
    </jml:setup>
    <jml:punchline>
      The second cow replies: "Hey, I was just gonna say that"!
    </jml:punchline>
  </jml:joke>

  </jml:collection>