application.yml

server:
  port: 8081
spring:
  #数据库连接配置
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/_6_29?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC
    username: root
    password: 123456

#mybatis的相关配置
mybatis:
  #mapper配置文件
  mapper-location: classpath:mapper/*.xml

mapper

<?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.example.demo.mapper.UserMapper">
    <select id="findAll" resultType="com.example.demo.entity.User">
        SELECT * FROM user
    </select>
</mapper>