一、实现流程

在接口处添加方法

package top.ltyzqhh.dao;

import top.ltyzqhh.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);
    //插入一个用户
    int addUser(User user);
    //修改用户
    int updateUser(User user);
    //删除一个用户
    int deleteUser(int id);

Mapper.xml实现接口

<?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>">

<!--命名空间namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="top.ltyzqhh.dao.UserMapper">

    <select id="getUserList" resultType="top.ltyzqhh.pojo.User">
        select * from mybatis.user;
    </select>
    <select id="getUserById" parameterType="int" resultType="top.ltyzqhh.pojo.User" >
        select * from mybatis.user where id=#{id}
    </select>
    <insert id="addUser" parameterType="top.ltyzqhh.pojo.User" >
        INSERT INTO mybatis.user (id, name, password) VALUES (#{id},#{name},#{password});
    </insert>
    <update id="updateUser" parameterType="top.ltyzqhh.pojo.User">
        update mybatis.user set  name=#{name},password=#{password}  where id=#{id};
    </update>

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

二、增删改查(测试)

增

1、修改xml（实现接口）

 <insert id="addUser" parameterType="top.ltyzqhh.pojo.User" >
        INSERT INTO mybatis.user (id, name, password) VALUES (#{id},#{name},#{password});
    </insert>

2.创建SqlSession，获取接口实例（xml实现的），最后增删改提交事务，关闭SqlSession流

public void addUser(){

        SqlSession sqlSession = Mybatis_utils.getSqlSession();

        try {
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            int sqldown = mapper.addUser(new User(5, "赵六", "123456"));

            if (sqldown>0){
                System.out.println("插入成功");
            }
            //提交事务
            sqlSession.commit();
        }finally {

            sqlSession.close();
        }
    }

删

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

public void delect(){
        SqlSession sqlSession = Mybatis_utils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int i = mapper.deleteUser(5);
        if (i>0){
            System.out.println("成功删除");
        }
        sqlSession.commit();
        sqlSession.close();
    }

改

<update id="updateUser" parameterType="top.ltyzqhh.pojo.User">
        update mybatis.user set  name=#{name},password=#{password}  where id=#{id};
    </update>

public void update(){
        SqlSession sqlSession = Mybatis_utils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        int i = mapper.updateUser(new User(1, "内河大魔王", "123"));
        if (i>0){
            System.out.println("成功修改");
        }
        sqlSession.commit();
        sqlSession.close();
    }

查

<select id="getUserById" parameterType="int" resultType="top.ltyzqhh.pojo.User" >
        select * from mybatis.user where id=#{id}
    </select>