@Override
  public void writeExternal(final Element element) throws WriteExternalException {
    final TreeSet<ConfigFileInfo> sortedConfigFiles = new TreeSet<>((o1, o2) -> {
      final int id = Comparing.compare(o1.getMetaData().getId(), o2.getMetaData().getId());
      return id != 0 ? id : Comparing.compare(o1.getUrl(), o2.getUrl());
    });
    sortedConfigFiles.addAll(configFiles.values());
    for (ConfigFileInfo configuration : sortedConfigFiles) {
      final Element child = new Element(ELEMENT_NAME);
      final ConfigFileMetaData metaData = configuration.getMetaData();
      child.setAttribute(ID_ATTRIBUTE, metaData.getId());
      child.setAttribute(URL_ATTRIBUTE, configuration.getUrl());
      element.addContent(child);
    }
  }
@Override
  public void writeExternal(final Element element)