Java HTML/XML - 如何使用jaxb在XML中执行自动增量ID

import java.util.ArrayList;
import java.util.List;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

public class Main {

  public static void main(String[] args) throws Exception {
    JAXBContext jc = JAXBContext.newInstance(Messages.class);

    Messages messages = new Messages();
    messages.getMessages().add(new Message());
    messages.getMessages().add(new Message());
    messages.getMessages().add(new Message());

    Marshaller marshaller = jc.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
    marshaller.setAdapter(new IDAdapter());
    marshaller.marshal(messages, System.out);
  }

  @XmlAccessorType(XmlAccessType.FIELD)
  public static class Message {

    @XmlAttribute
    @XmlJavaTypeAdapter(IDAdapter.class)
    private Integer id = 0;

  }

  public static class IDAdapter extends XmlAdapter<Integer, Integer> {

    private int counter = 1;

    @Override
    public Integer unmarshal(Integer v) throws Exception {
      return v;
    }

    @Override
    public Integer marshal(Integer v) throws Exception {
      return counter++;
    }

  }

  @XmlRootElement(name = "Messages")
  @XmlAccessorType(XmlAccessType.FIELD)
  public static class Messages {

    @XmlElement(name = "Message")
    private List<Message> messages = new ArrayList<Message>();

    public List<Message> getMessages() {
      return messages;
    }

  }
}