JAXB @XmlElement with more names

Question

I have an xml with an envelope, in the envelope a header, in the header there is an element called Period with a Startdate and an Enddate. But in some cases they're called StartDate and EndDate. Is there some way of saying to JAXB to look for both when unmarshalling?

I already have a class Envelope with in there bunch of classes for all the element parents I need with each having child elements if needed. One of them is the class Period with in there the two @XmlElement public String ***date.

I parse this with unmarshall and then access the data in my InsertProcessor to put them in queries and save it to a DB.

I tried using @XmlElements({}) but that didn't work:

@XmlElements({
    @XmlElement(name = "Startdate", type = Startdate.class),
    @XmlElement(name = "StartDate", type = StartDate.class)
})
private DateStart startdate;
@XmlElements({
    @XmlElement(name = "Enddate", type = Enddate.class),
    @XmlElement(name = "EndDate", type = EndDate.class)
})
private DateEnd enddate;

public Startdatum getStartdate() {
   return startdate;
}

public Stopdatum getEnddate() {
   return enddate;
}

abstract class DateStart{}

private class Startdate extends DateStart{}

private class StartDate extends DateStart{}

abstract class DateEnd{}

private class Enddate extends DateEnd{}

private class EndDate extends DateEnd{}

trying to access it in InsertProcessor.java with env.Header.Period.getStartdate();

IDE responding with Incompatible types. Required String, Found Parser.Startdatum

Sample.xml

<envelope>
 <data>
  <msgcode>441</msgcode>
  <msgdate>201903151120000</msgdate>
 </data>
 <Message>
  <Header>
   <Period>
     <Startdate>2018-05-01</Startdate> <!-- can also be StartDate -->
     <Enddate>2018-05-31</Enddate> <!-- can also be EndDate -->
   </Period>
  </Header>
 </Message>
</envelope>

Parser.java

public class Parser {
 public static Envelope parse (String xml) throws JAXBException, SAXException {
  JAXBContext jc;
  jc = JAXBContent.newInstance(Envelope.class)
  Unmarshaller u = jc.createUnmarshaller();
  ...
  InputSource is = new InputSource(new StringReader(xml));
  return (Envelope) u.unmarshal(new SAXSource(inFiler, inputSource));
 }
 @XmlRootElement(name="Envelope")
 public static class Envelope {
  @XmlElement(name = "Data")
  public Data Data;
  @XmlElement(name = "Message")
 public Message Message;
 }
 ...
 public static class Message {
 @XmlElement(name = "Header")
 public Header Header;
 ...
 }
 public static class Header {
 @XmlElement(name = "Period")
 public Period Period;
 ...
 }
 public static class Period {
 @XmlElement(name = "Startdate")
 public String Startdate;
 @XmlElement(name = "Enddate")
 public String Enddate;
 }
...
}

InsertProcessor.java:

public class InsertProcessor {
 public void process(String xml) throws Exception {
  Parser.Envelope env = Parser.parse(xml);
  String id = env.Header.Identification;
  ...
  String Startdate = env.Header.Period.Startdate;
  String Enddate = env.Header.Period.Enddate;

  try (Connection c = Db.getConnection()) {
   PreparedStatement ps = c.prepareStatement("insert into...");
    ps.setString(1, id)
    ...
    ps.setString(9, Startdate);
    ps.setString(10, Enddate);
    ps.execute();
  }
}

So I need to get either Start/Enddate or Start/EndDate. Right now I'm just getting Start/Enddate