private Element getDescription(String task) {

    if (task != null) {

      if (task.equals("define")) return definer.getDescription();

      if (task.equals("compare")) return comparer.getDescription();

      if (task.equals("search")) return searcher.getDescription();

      if (task.equals("wikify")) return wikifier.getDescription();
    }

    Element description = doc.createElement("Description");

    description.appendChild(
        createElement(
            "Details",
            "<p>This servlet provides a range of services for mining information from Wikipedia. Further details depend on what you want to do.</p>"
                + "<p>You can <a href=\""
                + context.getInitParameter("service_name")
                + "?task=search&help\">search for pages</a>, <a href=\""
                + context.getInitParameter("service_name")
                + "?task=compare&help\">measure how terms or articles related to each other</a>, <a href=\""
                + context.getInitParameter("service_name")
                + "?task=define&help\">obtain short definitions from articles</a>, and <a href=\""
                + context.getInitParameter("service_name")
                + "?task=wikify&help\">detect topics in web pages</a>.</p>"));

    Element paramTask =
        createElement(
            "Parameter",
            "Specifies what you want to do: can be <em>search</em>, <em>compare</em>, <em>define</em>, or <em>wikify</em>");
    paramTask.setAttribute("name", "task");
    description.appendChild(paramTask);

    Element paramId = doc.createElement("Parameter");
    paramId.setAttribute("name", "help");
    paramId.appendChild(doc.createTextNode("Specifies that you want help about the service."));
    description.appendChild(paramId);

    return description;
  }
  public void init(ServletConfig config) throws ServletException {
    super.init(config);
    context = config.getServletContext();

    TextProcessor tp = new CaseFolder();

    try {
      wikipedia =
          new Wikipedia(
              context.getInitParameter("mysql_server"),
              context.getInitParameter("mysql_database"),
              context.getInitParameter("mysql_user"),
              context.getInitParameter("mysql_password"));
    } catch (Exception e) {
      throw new ServletException("Could not connect to wikipedia database.");
    }

    // Escaper escaper = new Escaper() ;

    definer = new Definer(this);
    comparer = new Comparer(this);
    searcher = new Searcher(this);

    try {
      wikifier = new Wikifier(this, tp);

    } catch (Exception e) {
      System.err.println("Could not initialize wikifier");
    }

    try {
      File dataDirectory = new File(context.getInitParameter("data_directory"));

      if (!dataDirectory.exists() || !dataDirectory.isDirectory()) {
        throw new Exception();
      }

      cachingThread = new CacherThread(dataDirectory, tp);
      cachingThread.start();
    } catch (Exception e) {
      throw new ServletException("Could not locate wikipedia data directory.");
    }

    try {
      TransformerFactory tf = TransformerFactory.newInstance();

      transformersByName = new HashMap<String, Transformer>();
      transformersByName.put(
          "help", buildTransformer("help", new File("/research/wikipediaminer/web/xsl"), tf));
      transformersByName.put(
          "loading", buildTransformer("loading", new File("/research/wikipediaminer/web/xsl"), tf));
      transformersByName.put(
          "search", buildTransformer("search", new File("/research/wikipediaminer/web/xsl"), tf));
      transformersByName.put(
          "compare", buildTransformer("compare", new File("/research/wikipediaminer/web/xsl"), tf));
      transformersByName.put(
          "wikify", buildTransformer("wikify", new File("/research/wikipediaminer/web/xsl"), tf));

      Transformer serializer = TransformerFactory.newInstance().newTransformer();
      serializer.setOutputProperty(OutputKeys.INDENT, "yes");
      serializer.setOutputProperty(OutputKeys.METHOD, "xml");
      serializer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "3");
      transformersByName.put("serializer", serializer);

    } catch (Exception e) {
      throw new ServletException("Could not load xslt library.");
    }
  }
  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws IOException, ServletException {

    try {

      response.setHeader("Cache-Control", "no-cache");
      response.setCharacterEncoding("UTF-8");

      String task = request.getParameter("task");

      Element data = null;

      // process help request
      if (request.getParameter("help") != null) data = getDescription(task);

      // redirect to home page if there is no task
      if (data == null && task == null) {
        response.setContentType("text/html");
        response
            .getWriter()
            .append(
                "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 Transitional//EN\"><html><head><meta http-equiv=\"REFRESH\" content=\"0;url="
                    + context.getInitParameter("server_path")
                    + "></head><body></body></html>");
        return;
      }

      // process definition request
      if (data == null && task.equals("define")) {
        int id = resolveIntegerArg(request.getParameter("id"), -1);
        int length = resolveIntegerArg(request.getParameter("length"), definer.getDefaultLength());
        int format = resolveIntegerArg(request.getParameter("format"), definer.getDefaultFormat());
        int maxImageWidth =
            resolveIntegerArg(
                request.getParameter("maxImageWidth"), definer.getDefaultMaxImageWidth());
        int maxImageHeight =
            resolveIntegerArg(
                request.getParameter("maxImageHeight"), definer.getDefaultMaxImageHeight());
        int linkDestination =
            resolveIntegerArg(
                request.getParameter("linkDestination"), definer.getDefaultLinkDestination());
        boolean getImages = resolveBooleanArg(request.getParameter("getImages"), false);

        data =
            definer.getDefinition(
                id, length, format, linkDestination, getImages, maxImageWidth, maxImageHeight);
      }

      // all of the remaining tasks require data to be cached, so lets make sure that is finished
      // before continuing.
      if (!cachingThread.isOk()) throw new ServletException("Could not cache wikipedia data");

      double progress = cachingThread.getProgress();
      if (data == null && (progress < 1 || task.equals("progress"))) {
        // still caching up data, not ready to return a response yet.

        data = doc.createElement("loading");
        data.setAttribute("progress", df.format(progress));
        task = "loading";
      }

      // process search request
      if (data == null && task.equals("search")) {
        String term = request.getParameter("term");
        String id = request.getParameter("id");
        int linkLimit =
            resolveIntegerArg(request.getParameter("linkLimit"), searcher.getDefaultMaxLinkCount());
        int senseLimit =
            resolveIntegerArg(
                request.getParameter("senseLimit"), searcher.getDefaultMaxSenseCount());

        if (id == null) data = searcher.doSearch(term, linkLimit, senseLimit);
        else data = searcher.doSearch(Integer.parseInt(id), linkLimit);
      }

      // process compare request
      if (data == null && task.equals("compare")) {
        String term1 = request.getParameter("term1");
        String term2 = request.getParameter("term2");
        int linkLimit =
            resolveIntegerArg(request.getParameter("linkLimit"), comparer.getDefaultMaxLinkCount());
        boolean details =
            resolveBooleanArg(request.getParameter("details"), comparer.getDefaultShowDetails());

        data = comparer.getRelatedness(term1, term2, details, linkLimit);
      }

      // process wikify request
      if (data == null && task.equals("wikify")) {

        if (this.wikifier == null)
          throw new ServletException(
              "Wikifier is not available. You must configure the servlet so that it has access to link detection and disambiguation models.");

        String source = request.getParameter("source");
        int sourceMode =
            resolveIntegerArg(request.getParameter("sourceMode"), Wikifier.SOURCE_AUTODETECT);
        String linkColor = request.getParameter("linkColor");
        String baseColor = request.getParameter("baseColor");
        double minProb =
            resolveDoubleArg(
                request.getParameter("minProbability"), wikifier.getDefaultMinProbability());
        int repeatMode =
            resolveIntegerArg(request.getParameter("repeatMode"), wikifier.getDefaultRepeatMode());
        boolean showTooltips =
            resolveBooleanArg(
                request.getParameter("showTooltips"), wikifier.getDefaultShowTooltips());
        String bannedTopics = request.getParameter("bannedTopics");

        boolean wrapInXml = resolveBooleanArg(request.getParameter("wrapInXml"), true);

        if (wrapInXml) {
          data =
              wikifier.wikifyAndWrapInXML(
                  source,
                  sourceMode,
                  minProb,
                  repeatMode,
                  bannedTopics,
                  baseColor,
                  linkColor,
                  showTooltips);
        } else {
          response.setContentType("text/html");
          response
              .getWriter()
              .append(
                  wikifier.wikify(
                      source,
                      sourceMode,
                      minProb,
                      repeatMode,
                      bannedTopics,
                      baseColor,
                      linkColor,
                      showTooltips));
          return;
        }
      }

      if (data == null) throw new Exception("Unknown Task");

      // wrap data
      Element wrapper = doc.createElement("WikipediaMinerResponse");
      wrapper.setAttribute("server_path", context.getInitParameter("server_path"));
      wrapper.setAttribute("service_name", context.getInitParameter("service_name"));
      wrapper.appendChild(data);

      data = wrapper;

      // Transform or serialize xml data as appropriate

      Transformer tf = null;

      if (request.getParameter("xml") == null) {
        // we need to transform the data into html
        tf = transformersByName.get(task);

        if (request.getParameter("help") != null) tf = transformersByName.get("help");
      }

      if (tf == null) {
        // we need to serialize the data as xml
        tf = transformersByName.get("serializer");
        response.setContentType("application/xml");
      } else {
        // output will be transformed to html
        response.setContentType("text/html");
        response
            .getWriter()
            .append(
                "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN\" \"http://www.w3.org/TR/html4/strict.dtd\">\n");
      }

      tf.transform(new DOMSource(data), new StreamResult(response.getWriter()));

    } catch (Exception error) {
      response.reset();
      response.setContentType("application/xml");
      response.setHeader("Cache-Control", "no-cache");
      response.setCharacterEncoding("UTF8");

      Element xmlError = doc.createElement("Error");
      if (error.getMessage() != null) xmlError.setAttribute("message", error.getMessage());

      Element xmlStackTrace = doc.createElement("StackTrace");
      xmlError.appendChild(xmlStackTrace);

      for (StackTraceElement ste : error.getStackTrace()) {

        Element xmlSte = doc.createElement("StackTraceElement");
        xmlSte.setAttribute("message", ste.toString());
        xmlStackTrace.appendChild(xmlSte);
      }
      try {
        transformersByName
            .get("serializer")
            .transform(new DOMSource(xmlError), new StreamResult(response.getWriter()));
      } catch (Exception e) {
        // TODO: something for when an error is thrown processing an error????

      }
      ;
    }
  }