code: private URL getRequiredUrlParameter(String keyword,
                                          Map<String, String> parms) {
          String urlString = getRequiredParameter(keyword, parms);
          try {
              return new URL(urlString);
          } catch (MalformedURLException e) {
              throw new ValidatorProcessUsageException("Value '" + urlString
                      + "' for parameter '" + keyword + "' is not a valid URL: "
                      + e.getMessage());
          }
      }
docs: Get the requested parameter from the map. Complain if not found, or not a
  valid URL.