mybatis多对多查询

mybatis多对多查询

多对多关系其实我们看成是双向的一对多关系

需求：实现用户和角色的多对多查询

1、用户实体类

package com.yl.bean;

import java.io.Serializable;
import java.sql.Date;
import java.util.List;

/**
 * 用户实体类
 */
public class User implements Serializable {
    private Integer id;//id
    private String username;//用户名
    private Date birthday;//生日
    private String sex;//性别
    private String address;//地址
    private List<Role> roleList;//用户所包含的角色

    public User() {
    }

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public List<Role> getRoleList() {
        return roleList;
    }

    public void setRoleList(List<Role> roleList) {
        this.roleList = roleList;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

2、角色实体类

package com.yl.bean;

import java.io.Serializable;
import java.util.List;

/**
 * 角色实体类
 */
public class Role implements Serializable {
    private Integer id;//id
    private String name;//姓名
    private String desc;//描述
    private List<User> userList;//角色所包含的用户

    public Role() {
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    public List<User> getUserList() {
        return userList;
    }

    public void setUserList(List<User> userList) {
        this.userList = userList;
    }

    @Override
    public String toString() {
        return "Role{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", desc='" + desc + '\'' +
                '}';
    }
}

3、用户持久层接口

package com.yl.dao;

import com.yl.bean.User;

import java.util.List;

/**
 * 用户持久层接口
 */
public interface IUserDao {

    /**
     * 查询所有用户
     */
    List<User> queryAll();
}

4、角色持久层接口

package com.yl.dao;

import com.yl.bean.Role;

import java.util.List;

/**
 * 角色持久层接口
 */
public interface IRoleDao {

    /**
     * 查询所有
     */
    List<Role> queryAll();

}

5、全局配置文件

<?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>
    <!--配置别名-->
    <typeAliases>
        <package name="com.yl.bean"/>
    </typeAliases>

    <!--配置mybatis环境-->
    <environments default="mysql">
        <!--配置mysql环境-->
        <environment id="mysql">
            <!--事务类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!--数据源-->
            <dataSource type="POOLED">
               <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf8&amp;serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!--指定映射配置文件位置-->
    <mappers>
        <mapper resource="IUserDao.xml"></mapper>
        <mapper resource="IRoleDao.xml"></mapper>
    </mappers>
</configuration>

6、用户映射配置文件

<?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.yl.dao.IUserDao">
    <!--配置用户实体类和数据库的对应信息-->
    <resultMap id="userMap" type="com.yl.bean.User">
        <id property="id" column="id"></id>
        <result property="username" column="username"></result>
        <result property="birthday" column="birthday"></result>
        <result property="sex" column="sex"></result>
        <result property="address" column="address"></result>
        <!--多对多映射关系-->
        <collection property="roleList" ofType="com.yl.bean.Role">
            <id property="id" column="rid"></id>
            <result property="name" column="role_name"></result>
            <result property="desc" column="role_desc"></result>
        </collection>
    </resultMap>

    <!--查询所有用户-->
    <select id="queryAll" resultMap="userMap">
        SELECT u.*,r.`ID` rid,r.`ROLE_DESC`,r.`ROLE_NAME` FROM USER u LEFT OUTER JOIN user_role ur
        ON u.`ID`=ur.uid
        LEFT OUTER JOIN role r
        ON r.`id`=ur.rid
    </select>

</mapper>

7、角色映射配置文件

<?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.yl.dao.IRoleDao">
    <!--配置角色实体类和数据库的对应信息-->
    <resultMap id="roleMap" type="com.yl.bean.Role">
        <id property="id" column="rid"></id>
        <result property="name" column="role_name"></result>
        <result property="desc" column="role_desc"></result>
        <!--多对多映射关系-->
        <collection property="userList" ofType="com.yl.bean.User">
            <id property="id" column="id"></id>
            <result property="username" column="username"></result>
            <result property="birthday" column="birthday"></result>
            <result property="sex" column="sex"></result>
            <result property="address" column="address"></result>
        </collection>
    </resultMap>

    <!--查询所有角色-->
    <select id="queryAll" resultMap="roleMap">
        SELECT u.*,r.`ID` rid,r.`ROLE_DESC`,r.`ROLE_NAME` FROM role r LEFT OUTER JOIN user_role ur
        ON r.`ID`=ur.rid
        LEFT OUTER JOIN USER u
        ON u.`id`=ur.`UID`
    </select>
</mapper>

8、用户测试类

package com.yl;

import com.yl.bean.Role;
import com.yl.bean.User;
import com.yl.dao.IRoleDao;
import com.yl.dao.IUserDao;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;


public class UserTest {
    private InputStream inputStream;
    private IUserDao userDao;
    private SqlSession sqlSession;

    @Before
    public void init() throws IOException {
        //读取配置文件
        inputStream= Resources.getResourceAsStream("SqlMapperConfig.xml");
        //创建工厂
        SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sessionFactory= factoryBuilder.build(inputStream);
        //创建SqlSession对象
        sqlSession=sessionFactory.openSession();
        //创建IUserDao接口代理对象
        userDao=sqlSession.getMapper(IUserDao.class);
    }

    @After
    public void after() throws IOException {
        //提交事务
        sqlSession.commit();;
        //关闭资源
        sqlSession.close();
        inputStream.close();
    }

    /**
     * 查询所有
     */
    @Test
    public void test01() throws IOException {
        //查询所有角色
        List<User> userList=userDao.queryAll();
        //遍历输出
        for (User user:userList){
            System.out.println(user);
            System.out.println(user.getRoleList());
        }
    }

}

9、角色测试类

package com.yl;

import com.yl.bean.Role;
import com.yl.dao.IRoleDao;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;


public class RoleTest {
    private InputStream inputStream;
    private IRoleDao roleDao;
    private SqlSession sqlSession;

    @Before
    public void init() throws IOException {
        //读取配置文件
        inputStream= Resources.getResourceAsStream("SqlMapperConfig.xml");
        //创建工厂
        SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sessionFactory= factoryBuilder.build(inputStream);
        //创建SqlSession对象
        sqlSession=sessionFactory.openSession();
        //创建IUserDao接口代理对象
        roleDao=sqlSession.getMapper(IRoleDao.class);
    }

    @After
    public void after() throws IOException {
        //提交事务
        sqlSession.commit();;
        //关闭资源
        sqlSession.close();
        inputStream.close();
    }

    /**
     * 查询所有
     */
    @Test
    public void test01() throws IOException {
        //查询所有角色
        List<Role> roleList=roleDao.queryAll();
        //遍历输出
        for (Role role:roleList){
            System.out.println(role);
            System.out.println(role.getUserList());
        }
    }

}