SSM15.3【Mybatis：Mybatis的多表操作之多对多】

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

package com.haifei.domain;

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

/**
 * user表
 *  sys_user_role表
 */
public class User {

    private int id;
    private String username;
    private String password;
    private Date birthday;

   
    //描述的是当前用户具备哪些角色
    private List<Role> roleList;
    public List<Role> getRoleList() {
        return roleList;
    }
    public void setRoleList(List<Role> roleList) {
        this.roleList = roleList;
    }

    public Date getBirthday() {
        return birthday;
    }

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

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

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

    public String getPassword() {
        return password;
    }

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

    //m:n
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", birthday=" + birthday +
                ", roleList=" + roleList +
                '}';
    }
}

package com.haifei.domain;

/**
 * sys_role表
 *  sys_user_role表
 */
public class Role {

    private int id;
    private String roleName;
    private String roleDesc;

    public int getId() {
        return id;
    }

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

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

    public String getRoleDesc() {
        return roleDesc;
    }

    public void setRoleDesc(String roleDesc) {
        this.roleDesc = roleDesc;
    }

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

package com.haifei.mapper;

import com.haifei.domain.User;

import java.util.List;

public interface UserMapper {

    public List<User> findUserAndRoleAll();

}

<?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.haifei.mapper.UserMapper">

    <resultMap id="userRoleMap" type="user">
        <!--user的信息-->
        <id column="userId" property="id"></id>
        <result column="username" property="username"></result>
        <result column="password" property="password"></result>
        <result column="birthday" property="birthday"></result>
        <!--user内部的roleList信息-->
        <collection property="roleList" ofType="role">
            <id column="roleId" property="id"></id>
            <result column="roleName" property="roleName"></result>
            <result column="roleDesc" property="roleDesc"></result>
        </collection>
    </resultMap>

    <select id="findUserAndRoleAll" resultMap="userRoleMap">
       SELECT * FROM user u,sys_user_role ur,sys_role r WHERE u.id=ur.userId AND ur.roleId=r.id
    </select>
</mapper>

 

/**
     * 多对多查询
     *  场景：每个用户都可以拥有多种角色
     * @throws IOException
     */
    @Test
    public void test3() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.findUserAndRoleAll();
        for (User user : userList) {
            System.out.println(user);
        }
        /*
        User{id=1, username='zhangsan', password='123', birthday=Sat Jul 24 20:00:29 CST 2021, roleList=[Role{id=1, roleName='院长', roleDesc='负责全面工作'}, Role{id=2, roleName='研究员', roleDesc='课程研发工作'}]}
        User{id=2, username='lisi', password='345', birthday=Sat Jul 24 20:00:29 CST 2021, roleList=[Role{id=2, roleName='研究员', roleDesc='课程研发工作'}, Role{id=3, roleName='讲师', roleDesc='授课工作'}]}
         */

        sqlSession.close();
    }