public class OffsetDateTimeAdapter extends XmlAdapter<String, OffsetDateTime> {

  @Override
  public OffsetDateTime unmarshal(final String iso8601) throws Exception {
    if (iso8601 == null || iso8601.isEmpty()) {
      return null;
    }
    return OffsetDateTime.parse(iso8601);
  }

  @Override
  public String marshal(final OffsetDateTime odt) throws Exception {
    if (odt == null) {
      return null;
    }
    return odt.toString(); // ISO-8601-Format
  }
}