1.更改mapper子工程的application.yml，修改连接的数据库

spring:
  datasource:
    druid:
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/fmmall2?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8
      username: root
      password: 123456

mybatis:
  mapper-locations: classpath:mappers/*Mapper.xml
  type-aliases-package: com.qfedu.fmmall.entity

2.创建user实体类

beans-src-main-java-com.qfedu.fmmall.entity- User.java:

package com.qfedu.fmmall.entity;

import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@NoArgsConstructor
@AllArgsConstructor
@ApiModel(value = "User对象",description = "买家信息")
public class User {

    private int userId;
    private String username;
    private String password;
    private String nickname;
    private String realname;
    private String userImg;
    private String userMobile;
    private String userEmail;
    private String userSex;
    private Date userBirth;
    private Date userRegtime;
    private Date userModtime;
    
}

2.创建DAO接口，定义操作方法。

mapper-src-main-java-com.qfedu.fmmall.dao- UserDAO.java:

package com.qfedu.fmmall.dao;

import com.qfedu.fmmall.entity.User;

//@Repository
//@Mapper
public interface UserDAO {
    //用户注册
    public int insertUser(User user);
    
    //根据用户名查询用户信息
    public User queryUserByName(String name);
}

<?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.qfedu.fmmall.dao.UserDAO">

    <insert id="insertUser">
        insert into users(username,password,user_regtime,user_modtime)
        values(#{user.username},#{user.password},#{user.userRegtime},#{userModtime})
    </insert>

    <resultMap id="userMap" type="User">
        <id column="user_id" property=""/>
        <result column="username" property="username"/>
        <result column="password" property="password"/>
        <result column="nickname" property="nickname"/>
        <result column="realname" property="realname"/>
        <result column="user_img" property="userImg"/>
        <result column="user_mobile" property="userMobile"/>
        <result column="user_email" property="userEmail"/>
        <result column="user_sex" property="userSex"/>
        <result column="user_birth" property="userBirth"/>
        <result column="user_regtime" property="userRegtime"/>
        <result column="user_modtime" property="userModtime"/>
    </resultMap>
    
    <select id="queryUserByName" resultMap="userMap">
        select
            user_id,username,password,nickname,realname,user_img,user_mobile,
            user_email,user_sex,user_birth,user_regtime,user_modtime
        from users
        where username=#{name}
    </select>

</mapper>