hibernate进阶之集合关系映射

javabean设计

package cn.itcast.a_collection;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

// javabean设计
public class User {

private int userId;
private String userName;
// 一个用户，对应的多个地址
private Set<String> address;
private List<String> addressList = new ArrayList<String>();
//private String[] addressArray; // 映射方式和list一样 <array name=""></array>
private Map<String,String> addressMap = new HashMap<String, String>();

public Map<String, String> getAddressMap() {
return addressMap;
}
public void setAddressMap(Map<String, String> addressMap) {
this.addressMap = addressMap;
}
public List<String> getAddressList() {
return addressList;
}
public void setAddressList(List<String> addressList) {
this.addressList = addressList;
}
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public Set<String> getAddress() {
return address;
}
public void setAddress(Set<String> address) {
this.address = address;
}

}


User.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="cn.itcast.a_collection">
<class name="User" table="t_user">
<id name="userId" column="id">
<generator class="native"></generator>
</id>
<property name="userName"></property>

<!--
set集合属性的映射
name 指定要映射的set集合的属性
table 集合属性要映射到的表
key 指定集合表(t_address)的外键字段
element 指定集合表的其他字段
type 元素类型，一定要指定
-->
<set name="address" table="t_address">
<key column="uid"></key>
<element column="address" type="string"></element>
</set>

<!--
list集合映射
list-index 指定的是排序列的名称 (因为要保证list集合的有序)
-->
<list name="addressList" table="t_addressList">
<key column="uid"></key>
<list-index column="idx"></list-index>
<element column="address" type="string"></element>
</list>

<!--
map集合的映射
key 指定外键字段
map-key 指定map的key
element 指定map的value
-->
<map name="addressMap" table="t_addressMap">
<key column="uid"></key>
<map-key column="shortName" type="string" ></map-key>
<element column="address" type="string" ></element>
</map>
</class>
</hibernate-mapping>

测试类：App.java
package cn.itcast.a_collection;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.classic.Session;
import org.junit.Test;

public class App {

private static SessionFactory sf;
static {
sf = new Configuration()
.configure()
.addClass(User.class) // 测试时候使用
.buildSessionFactory();
}

// 保存set
@Test
public void testSaveSet() throws Exception {
Session session = sf.openSession();
session.beginTransaction();

//-- 保存
Set<String> addressSet = new HashSet<String>();
addressSet.add("广州");
addressSet.add("深圳");
// 用户对象
User user = new User();
user.setUserName("Jack");
user.setAddress(addressSet);

// 保存
session.save(user);

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

// 保存list/map
@Test
public void testSaveList() throws Exception {
Session session = sf.openSession();
session.beginTransaction();
User user = new User();
user.setUserName("Jason");
// 用户对象 -- list
user.getAddressList().add("珠海");
user.getAddressList().add("汕头");
// 保存
session.save(user);

// 用户对象 -- Map
user.getAddressMap().put("A0001", "广州");
user.getAddressMap().put("A0002", "深圳");

// 保存
session.save(user);

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

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

// 获取
User user = (User) session.get(User.class, 3); // 及时加载
System.out.println(user.getUserId());
System.out.println(user.getUserName());

// 当查询用户，同时可以获取用户关联的list集合的数据 (因为有正确映射)
// 当使用到集合数据的使用，才向数据库发送执行的sql语句 (懒加载)
System.out.println(user.getAddressList());

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