mybatis 多对多处理

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2024-09-14 10:55:28 215人阅读

下面的例子让新手看不错。可以改进的一点是

1、不必建立关联对象实体，可以用map传递两个id进去

2、文章的resultMap 继承和查询配置比较清楚，可以借鉴

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：

Sql代码

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：

Sql代码

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：

Sql代码

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：

Java代码

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：

Java代码

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：

Java代码

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代码

<?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>
<select id="selectUser" parameterType="long" resultMap="userMap">
select * from user where id = #{id}
</select>
<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>
<insert id="saveUser" parameterType="User" keyProperty="id"
useGeneratedKeys="true">
insert into user(name,password) values(#{name},#{password})
</insert>
<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代码

<?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>
<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
uug.user_id=u.id
<where>
<if test="id != 0 ">gi.id=#{id}</if>
<if test="name != null and name != ‘‘">
or gi.name = #{name}
</if>
</where>
</select>
<select id="selectGroup" parameterType="Date"
resultMap="groupMap">
select * from group_info where id=#{group_id}
</select>
<select id="getGroupByName" parameterType="String"
resultMap="groupMap">
select * from group_info where name=#{name}
</select>
<insert id="saveGroup" parameterType="Group" keyProperty="id"
useGeneratedKeys="true">
insert into group_info(name) values(#{name})
</insert>
<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>
<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>
<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代码

<?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：

Java代码

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
}
}
}

源码来源：minglisoft.cn/technology

mybatis 多对多处理

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