XMLWriter removes standalone attribute from XML header

[PAX523]

org.dom4j.io.XMLWriter.writeDeclaration() ignores the standalone attribute of the XML header from the input XML. The beautified XML result misses this attribute (even if it was in input XML).

  static String prettyXmlString(final String rawData) throws Exception {
      final Document document = DocumentHelper.parseText(rawData);
      try (StringWriter result = new StringWriter()) {
        final OutputFormat format = OutputFormat.createPrettyPrint();

        final XMLWriter writer = new XMLWriter(result, format);
        writer.write(document);
        writer.close();

        return result.toString();
     }
  }

  public static void main(final String[] args) throws Exception {
    String input = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\" ?><elem></elem>";
    System.out.println(prettyXmlString(input));

    input = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><elem></elem>";
    System.out.println(prettyXmlString(input));
  }

[PAX523]

I'd be glad when the formatter preserves all possible attributes in XML header that are present in the input XML.