SpringBoot_Mybatis_Login_Demo/src/main/resources/mapper/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">
<mapper namespace="com.bcn.login_mybatis_demo.mapper.UserMapper">

    <insert id="insertUser">
        insert into user
        values (null, #{uname}, #{uaccount}, #{upassword})
    </insert>

    <select id="selectUserByUact" resultType="com.bcn.login_mybatis_demo.pojo.User">
        select *
        from user
        where uaccount = #{uact}
    </select>

    <select id="selectUpwdByUact" resultType="java.lang.String">
        select upassword
        from user
        where uaccount = #{uact}
    </select>

</mapper>