注意事項

 * 下記のサンプルの「@XmlRootElement(name = "people" )」が重要で、ここで、XMLのルート要素を定義してあげる

 * プロパティに、Listのクラスを使用してもファイル出力するには、「@XmlElement」が必要
　　-----
    @XmlElement
    private List<Person> friends;
　　-----
　　 => これがないと、該当するプロパティがファイル出力されない。

サンプル

People.java

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

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name = "people")
public class People {
	public List<Person> people;
	
	public People() {
		this.people = new ArrayList<Person>();
	}
}

Person.java

public class Person {

    private String name;
	
    private int age;

    @XmlElement
    private List<Person> friends;

   public Person() {
      this.friends = new ArrayList<Person>();
   }

    public String getName() {
    	return this.name;
    }
    public void setName(String name) {
    	this.name = name;
    }
    
    public int getAge() {
    	return this.age;
    }
    public void setAge(int age) {
    	this.age = age;
    }

    public List<Person> getFriends() {
    	return this.friends;
    }
    public void addFriend(Person person) {
    	this.friends.add(person);
    }
}

HelloJaxb.java

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;

import javax.xml.bind.JAXB;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;

public class HelloJaxb {
	public static void main(String[] args) {
		People p = new People();

		Person person1 = new Person();
		person1.setName("Ken");
		person1.setAge(62);
		p.people.add(person1);

		Person person2 = new Person();
		person2.setName("Coco");
		person2.setAge(10);
		p.people.add(person2);

		// 書き込み
		try {
			JAXB.marshal(p, new FileOutputStream("people.xml"));
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

		// 読み込み
		try {		
			InputStream xmlInputStream = new FileInputStream("people.xml");
			JAXBContext jaxbContext = JAXBContext.newInstance(People.class);
			Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
			People newPeople = (People)unmarshaller.unmarshal(xmlInputStream);

			for (Person person : newPeople.people) {
				System.out.println(person.getName() + "(" + person.getAge()+ ")");
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}