hibernate4 映射集合属性List

package com.xxx.domain;

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

public class Person {

private Integer id;
private String name;
private Integer age;
private List<String> subject = new ArrayList<String>();

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public Integer getAge() {
return age;
}

public void setAge(Integer age) {
this.age = age;
}

public List<String> getSubject() {
return subject;
}

public void setSubject(List<String> subject) {
this.subject = subject;
}

}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" >

<hibernate-mapping package="com.xxx.domain">

<class name="Person" table="tb_person">
<id name="id" column="person_id">
<generator class="native"/>
</id>
<property name="name" column="name" type="string"/>
<property name="age" column="age" type="integer"/>
<list name="subject" table="tb_subject">
<key column="person_id"/>
<list-index column="index_id"/>
<element column="value" type="string" />
</list>
</class>

</hibernate-mapping>

public class PersonTest {

private SessionFactory sessionFactory=null;

@Before
public void setUp() throws Exception {
Configuration config=new  Configuration().configure();
ServiceRegistry serviceRegistry=new StandardServiceRegistryBuilder().applySettings(config.getProperties()).build();
sessionFactory=config.buildSessionFactory(serviceRegistry);
}

@After
public void tearDown() throws Exception {
sessionFactory.close();
}

@Test
public void test() {
//this.add();
this.find();

}

public void add(){
Session session=sessionFactory.openSession();
Transaction ts= session.beginTransaction();
Person person=new Person();
person.setName("小辉");
person.setAge(22);
List<String> subject=person.getSubject();
subject.add("数学");
subject.add("语文");
subject.add("英语");
subject.add("物理");
subject.add("化学");
person.setSubject(subject);
session.save(person);
ts.commit();
}

public void find(){
Session session=sessionFactory.openSession();
Transaction ts= session.beginTransaction();
Person person=(Person)session.load(Person.class, 2);
System.out.println("用户名："+person.getName());
System.out.println("年龄："+person.getAge());
List<String> subject=person.getSubject();
Iterator item=subject.iterator();
while(item.hasNext()){
String name=(String)item.next();
System.out.println("科目："+name);
}
ts.commit();
}

}