Hibernate中的集合映射

1.定义实体

public class User {
private int userId;
private String userName;
private Set<String> address;
set...
get...
}

2.写映射文件

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.juaner.hibernate.address">
<class name="User" table="t_user">
<id name="userId" column="u_id">
<generator class="native"/>
</id>
<property name="userName" column="u_name"/>
<set name="address" table="t_address">
<!--外键字段-->
<key column="u_id"></key>
<!--其他字段，没有bean与其对应，必须制定type-->
<element column="address" type="string"></element>
</set>
<!--list有先后顺序，list-index制定排序列的名称-->
<!--<list name="addressList" table="t_addresslist">-->
<!--<key column="u_id"></key>-->
<!--<list-index column="idx"></list-index>-->
<!--<element column="address" type="string"></element>-->
<!--</list>-->
</class>

</hibernate-mapping>

3.保存数据

@Test
public void testSave()throws Exception{
Session session = sf.openSession();
session.beginTransaction();

Set<String> address = new HashSet<String>();
address.add("广州");
address.add("北京");

User user = new User();
user.setUserName("jack");
user.setAddress(address);
session.save(user);
session.getTransaction().commit();
session.close();
}

4.结果

5.获取数据

@Test
public void test3()throws Exception{
Session session = sf.openSession();
session.beginTransaction();

User user = (User) session.get(User.class, 1);
System.out.println(user);
//当查询用户，同时可以获取用户关联的list集合的数据
//当使用到集合数据时，才向数据库发送执行的sql语句（懒加载，可以提高执行效率）
System.out.println(user.getAddressList());

session.getTransaction().commit();
session.close();
}