在Hibernate中配置多对多连接表

 

接前文在Hibernate中配置一对多连接表

其中表roomusers更改如下：

create table ROOMUSERS(
       USERID NUMBER(4),
       ROOMID NUMBER(4) not null
);

映射文件配置如下：
Room.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping package="com.cosmow.hibernatedemo2.entity">
    <class name="Room" table="ROOM" schema="STORE">
        <id name="id" type="java.lang.Long">
            <column name="ID" precision="4" scale="0" />
            <!-- Oracle数据库增长方式序列 -->
            <generator class="sequence">
                <param name="sequence">ROOM_SEQ</param>
            </generator>
        </id>
        <!-- 映射roomnumber属性 -->
        <property name="roomnumber" type="java.lang.String">
            <column name="ROOMNUMBER" length="11" not-null="true" />
        </property>
        <!-- 映射name属性 -->
        <property name="name" type="java.lang.String">
            <column name="NAME" length="32" not-null="true" />
        </property>
        <!-- 通过连接表的多端，因此需要table属性为roomusers -->
        <set name="users" cascade="all" table="roomusers">
            <!-- 该key的字段为连接表中的字段，作为外键 -->
            <key column="roomid" />
            <!-- 配置多对多 -->
            <many-to-many class="Userinfo" column="userid" />
        </set>
    </class>
</hibernate-mapping>

Userinfo.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping package="com.cosmow.hibernatedemo2.entity">
    <class name="Userinfo" table="USERINFO" schema="STORE">
        <id name="id" type="java.lang.Long">
            <column name="ID" precision="4" scale="0" />
            <!-- Oracle数据库增长方式序列 -->
            <generator class="sequence">
                <param name="sequence">USERINFO_SEQ</param>
            </generator>
        </id>
        <property name="name" type="java.lang.String">
            <column name="NAME" length="32" not-null="true" />
        </property>
        <property name="sex" type="java.lang.String">
            <column name="SEX" length="2" />
        </property>
        <set name="rooms" cascade="all" table="roomusers">
            <key column="userid" />
            <many-to-many class="Room" column="roomid" />
        </set>
    </class>
</hibernate-mapping>

测试代码如下：

/** *//**
 * Demo.java
 *
 * Copyright 2008. All Rights Reserved.
 */
package com.cosmow.hibernatedemo2.demo;

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

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.cosmow.HibernateSessionFactory;
import com.cosmow.hibernatedemo2.entity.Room;
import com.cosmow.hibernatedemo2.entity.Userinfo;

/** *//**
 * TODO
 * 
 * Revision History
 *
 * 2008-7-11,Cosmo,created it
 */
public class Demo {
    
    public void test() { 
        //第一个room实体
        Room room = new Room();
        room.setName("cosmoHome");
        room.setRoomnumber("001");
        
        //第二个room实体
        Room room2 = new Room();
        room2.setName("Home2");
        room2.setRoomnumber("002");

        //第一个user实体
        Userinfo user = new Userinfo();
        user.setName("cosmo");
        user.setSex("M");
        
        //第二个user实体
        Userinfo user2 = new Userinfo();
        user2.setName("winnie");
        user2.setSex("F");

        //创建第二个user实体与第二个room实体的关系，通过连接表维护关系
        Set<Room> roomSet = new HashSet<Room>();
        roomSet.add(room2);
        user2.setRooms(roomSet);
        
        //创建第一个room实体与第一、第二个user实体的关系，通过连接表维护关系
        //添加user实体到集合userSet
        Set<Userinfo> userSet = new HashSet<Userinfo>();
        userSet.add(user);
        userSet.add(user2);
        room.setUsers(userSet);

        // 启动Session
        Session session = HibernateSessionFactory.getSession();
        // 启动事务
        Transaction tx = session.beginTransaction();
        // 持久化room实体
        //此时将更新表room和userinfo以及维护关系的roomusers表
        session.save(room);
        tx.commit();
        HibernateSessionFactory.closeSession();
        
        // 启动Session
        session = HibernateSessionFactory.getSession();
        // 启动事务
        tx = session.beginTransaction();
        
        //获取Room实体以成为持久化状态，此时将获取room表的所有字段信息
        Room roomF1 = (Room)session.get(Room.class, room.getId());
        
        //通过外连接roomusers获取userinfo表对应字段信息
        Iterator<Userinfo> iF1 = roomF1.getUsers().iterator();
        while(iF1.hasNext()) { 
            Userinfo userF = iF1.next();
            System.out.println(userF.getId());
            System.out.println(userF.getName());
            System.out.println(userF.getSex());
        }
        
        Room roomF2 = (Room)session.get(Room.class, room2.getId());
        
        Iterator<Userinfo> iF2 = roomF2.getUsers().iterator();
        while(iF1.hasNext()) { 
            Userinfo userF = iF2.next();
            System.out.println(userF.getId());
            System.out.println(userF.getName());
            System.out.println(userF.getSex());
        }
        
        tx.commit();
        HibernateSessionFactory.closeSession();
    }

    public static void main(String[] args) {
        Demo demo = new Demo();
        demo.test();