code: @Override
      public String toExternalForm(URL url) {
          try {
              return (String) _toExternalForm.invoke(getInstance(), new Object[] { url });
          } catch (Exception e) {
              FFDCFilter.processException(e, getClass().getName(), "toExternalForm", url);
              return null;
          }
      }
docs: /*
  @see org.osgi.service.url.URLStreamHandlerService#toExternalForm(java.net.URL)