@Nullable
  private String addSchemeIfNoneSpecified(@Nullable String url) {
    if (StringUtil.isNotEmpty(url)) {
      try {
        final String scheme = new URI(url).getScheme();
        // For URL like "foo.bar:8080" host name will be parsed as scheme
        if (scheme == null) {
          url = getDefaultScheme() + "://" + url;
        }
      }
      catch (URISyntaxException ignored) {
      }
    }
    return url;
  }
@Nullable
  private String addSchemeIfNoneSpecified(@Nullable String url)