private Extractor getExtractor(ServletContext context, String id) {
    CompareRegistry registry =
        (CompareRegistry) context.getAttribute(CompareRegistry.class.getName());

    Collection<Extractor> Extractors = registry.getAvailableExtractors();
    Extractor extractor = null;
    for (Extractor e : Extractors) {
      if (e.getClass().getName().equals(id)) {
        extractor = e;
      }
    }
    return extractor;
  }
  @GET
  @Path("/{id}")
  @Produces("application/json")
  public Map<String, Object> getExtractorJSON(
      @PathParam("id") String id, @Context ServletContext context) {

    log.trace("/extractors/" + id + " requested");
    Extractor extractor = getExtractor(context, id);
    Map<String, Object> json = new HashMap<String, Object>();
    if (extractor != null) {
      json.put("name", extractor.getName());
      json.put("id", extractor.getClass().getName());
      json.put("supportedFeature", extractor.getFeatureType().getName());
    } else {
      json.put("Error", "Extractor not found");
    }
    return json;
  }
  @GET
  @Path("/")
  @Produces("application/json")
  public List<Map<String, Object>> listJSON(@Context ServletContext context) {

    log.trace("/extractors requested");
    Collection<Extractor> extractors = getExtractors(context);
    List<Map<String, Object>> jsonReturn = new ArrayList<Map<String, Object>>();
    if (extractors.size() == 0) {
      return jsonReturn;
    } else {
      for (Extractor extractor : extractors) {
        Map<String, Object> json = new HashMap<String, Object>();
        json.put("name", extractor.getName());
        json.put("id", extractor.getClass().toString());
        json.put("supportedFeature", extractor.getFeatureType().getName());
        jsonReturn.add(json);
      }
      return jsonReturn;
    }
  }
  @GET
  @Path("/")
  @Produces("text/html")
  public String listHTML(@Context ServletContext context) {

    log.trace("/extractors requested");
    Collection<Extractor> extractors = getExtractors(context);
    if (extractors.size() == 0) {
      return "No Extractors";
    } else {
      String content = new String("<h3>Versus > Extractors</h3><ul>");
      for (Extractor extractor : extractors) {
        content +=
            "<li><a href='extractors/"
                + extractor.getClass().getName()
                + "'>"
                + extractor.getClass().getName()
                + "</a></li>";
      }
      content += "</ul>";
      return content;
    }
  }