Mapper字段笔记

• namespace

namespace的包名要和UserMapper/UserDao接口报名一致

• id

id就是namespace中对应的方法名

• resultType

resultType是SQL语句返回值

• parameterType

参数类型

编写步骤

• 1. 编写接口
     UserMapper/UserDao:

package com.zzqsmile.dao;

import com.zzqsmile.pojo.User;

import java.util.List;

public interface UserMapper {
    //查询全部用户
    List<User> getUserList();

    //根据ID查询用户
    User getUserByID(int id);

    //增加用户
    int userAdd(User user);

    //修改用户
    int userUpd(User user);

    //删除用户
    int userDel(int id);
}

• 2. 编写对应的Mapper中的sql语句
     UserMapper.xml:

<?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">
<!--namespace绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.zzqsmile.dao.UserMapper">
    <!--select查询-->
    <select id="getUserList" resultType="com.zzqsmile.pojo.User">
        select * from mybatis.user
    </select>
    
    <select id="getUserByID" resultType="com.zzqsmile.pojo.User" parameterType="int">
        select * from mybatis.user where id = #{id}
    </select>

    <insert id="userAdd" parameterType="com.zzqsmile.pojo.User">
        insert into mybatis.user (id,name,pwd) values (#{id},#{name},#{pwd})
    </insert>

    <update id="userUpd" parameterType="com.zzqsmile.pojo.User">
        update mybatis.user set name = #{name},pwd = #{pwd} where id = #{id}
    </update>

    <delete id="userDel" parameterType="int">
        delete from mybatis.user where id = #{id}
    </delete>

</mapper>

• 3. 测试

package com.zzqsmile.dao;

import com.zzqsmile.pojo.User;
import com.zzqsmile.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {

    @Test
    public void Test(){
        //第一步：获取SqlSesson对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        try {
            //第二步：执行SQL
            //方式1：getMapper推荐使用
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            List<User> userList = mapper.getUserList();

            //方式2：
            //List<User> userList = sqlSession.selectList("com.zzqsmile.dao.UserDao.getUserList");

            for (User user : userList) {
                System.out.println(user);
            }

        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            //关闭sqlSession
            sqlSession.close();
        }
    }


    @Test
    public void getUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User userByID = mapper.getUserByID(1);
        System.out.println(userByID);
    }

    //增删改需要提交事物
    @Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int res = mapper.userAdd(new User(4, "zhangsan", "111111"));
        if (res>0){
            System.out.println("添加成功");
        }

        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void userUpd(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int res1 = mapper.userUpd(new User(4, "zhangsan", "123123"));
        if (res1>0){
            System.out.println("修改成功");
        }

        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void userDel(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int res2 = mapper.userDel(4);
        if (res2>0){
            System.out.println("删除成功");
        }

        //提交事务
        sqlSession.commit();
        sqlSession.close();
    }
}

注意，增删改需要提交事物才能生效

万能Map

• UserMapper:

//万能Map
    int userAdd2(Map<String,Object> map);

• UserMapper.xml

    <insert id="userAdd2" parameterType="map">
        insert into mybatis.user (id,pwd) values (#{id},#{userpwd})
    </insert>

• UserDaoTest

    @Test
    public void addUser2(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        HashMap<String, Object> stringObjectHashMap = new HashMap<String, Object>();
        stringObjectHashMap.put("id",5);
        stringObjectHashMap.put("userpwd","222222");

        mapper.userAdd2(stringObjectHashMap);

        //提交事务
        sqlSession.commit();

        sqlSession.close();
    }