MyBatis 多对多 处理

mybatis3.0添加了association和collection标签专门用于对多个相关实体类数据进行级联查询，但仍不支持多个相关实体类数据的级联保存和级联删除操作。因此在进行实体类多对多映射表设计时，需要专门建立一个关联对象类对相关实体类的关联关系进行描述。下文将以“User”和“Group"两个实体类之间的多对多关联映射为例进行CRUD操作。

建立user表，对应实体类"User"，建表语句如下：
<!--StartFragment--> 

CREATE TABLE `user` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(40) collate utf8_unicode_ci default NULL,
  `password` varchar(20) collate utf8_unicode_ci default NULL,
  `createtime` timestamp NULL default CURRENT_TIMESTAMP,
  PRIMARY KEY  (`id`)
)

建立group_info表，对应实体类"Group"，建表语句如下：

CREATE TABLE `group_info` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(40) collate utf8_unicode_ci default NULL,
  `createdate` timestamp NULL default CURRENT_TIMESTAMP,
  `state` int(1) default '0' COMMENT '0:可见;1:不可见',
  PRIMARY KEY  (`id`)
)

建立user_group表，对应实体类"UserGroupLink"(该类为User和Group两个实体类之间的关系描述)，建表语句如下：

CREATE TABLE `user_group` (
  `user_id` int(11) default NULL,
  `group_id` int(11) default NULL,
  `createdate` timestamp NULL default CURRENT_TIMESTAMP,
  KEY `FK_user_group_user_id` (`user_id`),
  KEY `FK_user_group_group_id` (`group_id`),
  CONSTRAINT `FK_user_group_group_id` FOREIGN KEY (`group_id`) REFERENCES `group_info` (`id`),
  CONSTRAINT `FK_user_group_user_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`)
)

建立实体类User，代码如下：

package com.xxt.ibatis.dbcp.domain;

import java.util.Date;
import java.util.List;

/**
 * @describe: User实体类
 * @author:    Nirvana
 * @version:   V1.0  2011-3-11下午06:06:49 create
 */

public class User {

    private long id;

    private String name;

    private String password;

    private Date createTime;

    private List<Group> group;

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public List<Group> getGroup() {
        return group;
    }

    public void setGroup(List<Group> group) {
        this.group = group;
    }
}

建立实体类Group,代码如下：

package com.xxt.ibatis.dbcp.domain;

import java.util.Date;
import java.util.List;

/**
 * @describe: Group实体类
 * @author: Nirvana
 * @version: V1.0 2011-3-7下午08:10:29 create
 */
public class Group {

    private long id;

    private String name; // 组名

    private Date createTime;

    private int state; // 0可见状态 1不可见状态

    private List<User> user;

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public int getState() {
        return state;
    }

    public void setState(int state) {
        this.state = state;
    }

    public List<User> getUser() {
        return user;
    }

    public void setUser(List<User> user) {
        this.user = user;
    }

}

建立实体类UserGroupLink，用于描述User和Group之间的对应关系，代码如下：

package com.xxt.ibatis.dbcp.domain;

import java.util.Date;

/**
 * @describe: 描述User和Group之间的映射关系
 * @author: Nirvana
 * @version: V1.0 2011-3-11下午02:57:52 create
 */
public class UserGroupLink {

    private User user;

    private Group group;

    private Date createTime;

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public Group getGroup() {
        return group;
    }

    public void setGroup(Group group) {
        this.group = group;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

建立user实体类的映射文件user.map.xml，代码如下：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper 
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.xxt.ibatis.dbcp.domain.User">
    <resultMap type="User" id="userMap">
        <id property="id" column="id" />
        <result property="name" column="name" />
        <result property="password" column="password" />
        <result property="createTime" column="createtime" />
    </resultMap>

    <resultMap type="User" id="userGroupMap" extends="userMap">
        <collection property="groups" ofType="Group">
            <id property="id" column="goupId" />
            <result property="name" column="groupName" />
            <result property="state" column="state" />
            <result property="createTime" column="groupCreateTime" />
        </collection>
    </resultMap>


    <!-- 根据user表中的id查询用户信息 -->
    <select id="selectUser" parameterType="long" resultMap="userMap">
        select * from user where id = #{id}
    </select>

    <!-- 根据user表中的id查询用户和组信息 -->
    <select id="selectUserGroup" parameterType="long"
        resultMap="userGroupMap">
        select u.id,u.name,u.password,u.createtime, gi.id as
        goupId,gi.name as groupName, gi.createdate as groupCreateTime,
        gi.state from user u left join user_group ug on u.id=ug.user_id
        left join group_info gi on ug.group_id=gi.id where u.id = #{id}
    </select>

    <!-- 插入用户信息 -->
    <insert id="saveUser" parameterType="User" keyProperty="id"
        useGeneratedKeys="true">
        insert into user(name,password) values(#{name},#{password})
    </insert>

    <!-- 保存用户和组之间的关系信息 -->
    <insert id="saveRelativity" parameterType="UserGroupLink">
        insert into user_group(user_id,group_id)
        values(#{user.id},#{group.id})
    </insert>

    <select id="selectAllUser" resultMap="userMap">
        select * from user
    </select>

</mapper>

建立group实体类的映射文件group.map.xml，代码如下:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper 
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.xxt.ibatis.dbcp.domain.Group">
    <resultMap type="Group" id="groupMap">
        <id property="id" column="id" />
        <result property="name" column="name" />
        <result property="createTime" column="createdate" />
    </resultMap>

    <resultMap type="Group" id="groupUserMap" extends="groupMap">
        <collection property="users" ofType="User">
            <id property="id" column="userId" />
            <result property="name" column="userName" />
            <result property="password" column="password" />
            <result property="createTime" column="userCreateTime" />
        </collection>
    </resultMap>


    <!-- 根据Group表中的id或name查询组信息和组内用户信息 -->
    <select id="selectGroupUser" parameterType="Group"
        resultMap="groupUserMap">
        select u.id as userId,u.name as userName,
        u.password,u.createtime as userCreateTime,
        gi.id,gi.name,gi.createdate,gi.state from group_info gi left
        join user_group ug on gi.id=ug.group_id left join user u on
        ug.user_id=u.id
        <where>
            <!--当id为初始值0，不再使用id作为查询条件 -->
            <if test="id != 0  ">gi.id=#{id}</if>
            <!-- 当name为空或为空串时，不再使用name作为查询条件 -->
            <if test="name != null and name != ''">
                or gi.name = #{name}
            </if>
        </where>
    </select>

    <!-- 根据id查询group组信息 -->
    <select id="selectGroup" parameterType="Date"
        resultMap="groupMap">
        select * from group_info where id=#{group_id}
    </select>

    <!--根据name查询group组信息  -->
    <select id="getGroupByName" parameterType="String"
        resultMap="groupMap">
        select * from group_info where name=#{name}
    </select>

    <!-- 插入组信息 -->
    <insert id="saveGroup" parameterType="Group" keyProperty="id"
        useGeneratedKeys="true">
        insert into group_info(name) values(#{name})
    </insert>

    <!-- 删除组与组内成员之间的对应关系 -->
    <delete id="deleteGroupUser" parameterType="UserGroupLink">
        delete from user_group
        <where>
            <if test="user.id != 0">user_id = #{user.id}</if>
            <if test="group.id != 0">and group_id = #{group.id}</if>
        </where>
    </delete>

    <!--根据组id或者组name删除组信息 -->
    <delete id="deleteGroup" parameterType="Group">
        delete from group_info
        <where>
            <if test="id!=0">id=#{id}</if>
            <if test="name!=null || name!=''">and name=#{name}</if>
        </where>
    </delete>

    <!-- 更新根据组id或者组name更新组状态 -->
    <update id="updateGroupState" parameterType="Group">
        update group_info set state=#{state}
        <where>
            <if test="id!=0">id=#{id}</if>
            <if test="name!=null || name!=''">and name=#{name}</if>
        </where>
    </update>
</mapper>

建立ibatis总配置文件salMapConfig.xml,代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration 
    PUBLIC "-//mybatis.org//DTD Config 3.0//EN" 
    "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="jdbc.properties" />

    <typeAliases>
        <typeAlias type="com.xxt.ibatis.dbcp.domain.User" alias="User" />
        <typeAlias type="com.xxt.ibatis.dbcp.domain.Group"
            alias="Group" />
        <typeAlias type="com.xxt.ibatis.dbcp.domain.UserGroupLink"
            alias="UserGroupLink" />
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="UNPOOLED">
                <property name="driver" value="${driver}" />
                <property name="url" value="${url}" />
                <property name="username" value="${username}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/xxt/ibatis/dbcp/domain/user.map.xml" />
        <mapper resource="com/xxt/ibatis/dbcp/domain/group.map.xml" />
    </mappers>
</configuration>

测试用例，代码如下：

package com.xxt.ibatis.dbcp.test;

import java.io.Reader;
import java.text.SimpleDateFormat;
import java.util.List;

import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;

import org.apache.ibatis.io.Resources;     
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.xxt.ibatis.dbcp.domain.Group;
import com.xxt.ibatis.dbcp.domain.User;
import com.xxt.ibatis.dbcp.domain.UserGroupLink;

/**
 * @describe: 测试用例
 * @author:    Nirvana
 * @version:   V1.0  2011-3-4下午03:21:17 create
 */
public class IbatisUserTest {

    private final static String IBATIS_CONFIG_XML  = "sqlMapConfig.xml"; 
    private static SqlSession session;
    private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd k:mm:ss");
          
    @BeforeClass
    public static void setUpBeforeClass() throws Exception {
         Reader reader = Resources.getResourceAsReader(IBATIS_CONFIG_XML);  //读取ibatis配置文件
         SqlSessionFactory sqlMapper = new SqlSessionFactoryBuilder().build(reader);
          session = sqlMapper.openSession(true);
          session.commit(false); //将默认提交事务属性设置为否
    }
    
    
    //保存用户信息
    @Test
    public void saveUserTest(){
        User user = new User();
        user.setName("张三");
        user.setPassword("123456");
        session.insert("com.xxt.ibatis.dbcp.domain.User.saveUser", user);
    }
   
    //获取用户信息
    @Test
    public void getUserTest(){
        User user = (User) session.selectOne("com.xxt.ibatis.dbcp.domain.User.selectUser", 1L);
        System.out.println("用户名： "+user.getName());
        System.out.println("用户密码:  "+user.getPassword());
        System.out.println("用户创建日期："+sdf.format(user.getCreateTime()));
    }
   
    //获取用户和用户所在组信息
    @Test
    public void getUserAndGroupTest(){
         User  user =  (User)session.selectOne("com.xxt.ibatis.dbcp.domain.User.selectUserGroup", 4L);
         
         System.out.println(user.getName() +"所属组信息:");
        for(Group group : user.getGroups() ){
            System.out.println("    组名:"+group.getName()+"，组创建时间:"+sdf.format(group.getCreateTime()));
        }
        
        
    }
    
    //保存用户和用户所在组信息
    //当用户所在组不存在时，创建该组，并生成映射关系
    @Test
    public void saveUserAndGroupTest(){
        User user = new User();
        user.setName("无常鬼");
        user.setPassword("wuchang");
        session.insert("com.xxt.ibatis.dbcp.domain.User.saveUser", user);
        
        Group groupImpl = (Group)session.selectOne("com.xxt.ibatis.dbcp.domain.Group.getGroupByName","用户组4");//获取组实例
        UserGroupLink ugl = new UserGroupLink();//声明User和Group实体间映射关系实例
        
        //查询到的组实例为空时的逻辑处理
        if(groupImpl == null){
             Group group = new Group();
             group.setName("用户组4");
            session.insert("com.xxt.ibatis.dbcp.domain.Group.saveGroup", group);//持久化创建好的组实例
            
            //设置映射关系实例相关的属性
            ugl.setUser(user);
            ugl.setGroup(group);
            session.insert("com.xxt.ibatis.dbcp.domain.User.saveRelativity",ugl);//持久化映射关系实力
                    
        }else{
            ugl.setGroup(groupImpl);
            ugl.setUser(user);
            session.insert("com.xxt.ibatis.dbcp.domain.User.saveRelativity",ugl);
        }
    }
    
    
    //删除组信息的同时，取消组内所有的成员与该组的关联关系
    @Test
    public void deleteGroupTest(){
        Group group = new Group();
        //group.setId(1L);  //以组id作为查询条件
        group.setName("用户组1"); //以组name作为查询条件
        Group groupImpl = (Group)session.selectOne("com.xxt.ibatis.dbcp.domain.Group.selectGroupUser",group);//获取组实例
        
        //组实例存在时
        if(groupImpl != null){
            
            List<User> users = groupImpl.getUsers();
            
          //查看用户组1中是否存在用户
            if(users != null && users.size() > 0){
                
                //存在用户时，先删除组与用户的对应关系
                UserGroupLink ugl = new UserGroupLink();
                for(User user : users){
                   ugl.setUser(user);
                   ugl.setGroup(groupImpl);
                   session.delete("com.xxt.ibatis.dbcp.domain.Group.deleteGroupUser",ugl );
                } 
            }
            //删除组信息
            session.delete("com.xxt.ibatis.dbcp.domain.Group.deleteGroup", groupImpl);
            
        }else{
            throw new RuntimeException("查询的组不存在!!");
        }
        
        
    }
    
    
    //更新组状态，当组状态由可见状态变成不可见时，取消该组下的用户与该组的映射关系
    @Test
    public void updateGroupStateTest(){
        Group group = new Group();
        group.setName("用户组2");
        Group groupImpl = (Group) session.selectOne("com.xxt.ibatis.dbcp.domain.Group.selectGroupUser",group);
        
        if(groupImpl != null){
            int state = groupImpl.getState() == 1 ? 0 : 1;
            
            
            //组状态由0变成1时，即由可见变为不可见
            if(state == 1){
                List<User> users = groupImpl.getUsers();
           //查看用户组2中是否存在用户
                if(users != null && users.size() > 0){
                    
                    //存在用户时，删除组与用户的对应关系
                    UserGroupLink ugl = new UserGroupLink();
                    for(User user : users){
                       ugl.setUser(user);
                       ugl.setGroup(groupImpl);
                       session.delete("com.xxt.ibatis.dbcp.domain.Group.deleteGroupUser",ugl );
                    } 
                }
            } 
            
            //更新组状态
            groupImpl.setState(state);
        }
        else{
            throw new RuntimeException("查询的组不存在!!");
        }
         
    }
    
    @AfterClass
    public static void tearDownAfterClass() throws Exception {
      if(session != null){
         session.commit(); //提交事务
         session.close(); //关闭连接
      }
    } 
}

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