Java HTML/XML - 如何元数枚举值

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.annotation.XmlEnum;
import javax.xml.bind.annotation.XmlRootElement;

public class Main {

  public static void main(String[] args) throws JAXBException {
    JAXBContext context = JAXBContext.newInstance(Card.class);
    context.createMarshaller().marshal(Card.CLUBS, System.out);
  }

}

@XmlRootElement
@XmlEnum(String.class)
enum Card {
  CLUBS, DIAMONDS, HEARTS, SPADES
}