Spring boot 使用QQ郵箱進行一個驗證登入功能

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/community?useUnicode=true&characterEncoding=utf8&useSSL=false
    username: root
    password: 123456
  mail:
    host: smtp.qq.com
    username: 自己的qq@qq.com
    password: 剛剛QQ郵箱那生成的那個字串，不是郵箱密碼
    default-encoding: UTF-8
    thymeleaf:
        cache: false

package com.example.community.controller;

import lombok.extern.slf4j.Slf4j;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import javax.mail.MessagingException;
import javax.mail.internet.MimeMessage;
import javax.servlet.http.HttpSession;

@Slf4j
@RestController()
@RequestMapping("/mail")
@CrossOrigin(origins = {"http://localhost:8090", "null"})
public class MailController {
    final String from="527734202@qq.com";
    @Resource
    JavaMailSender javaMailSender;
    @GetMapping("/sendMail")
    public void sendMail(String email , HttpSession session){
        MimeMessage mimeMessage = javaMailSender.createMimeMessage();
        try {
            MimeMessageHelper mimeMessageHelper = new MimeMessageHelper(mimeMessage, true);
//            設定發件人
            mimeMessageHelper.setFrom(from);
//            設定收件人
            mimeMessageHelper.setTo(email);
//            設定郵件主題
            mimeMessageHelper.setSubject("資訊管理驗證");
            //生成亂數
            String random = randomInteger();
            //將亂數放置到session中
            session.setAttribute("email",email);
            session.setAttribute("code",random);

//            設定驗證碼的樣式
            mimeMessageHelper.setText("<font style='color:green'>"+random+"</font>",true);

            javaMailSender.send(mimeMessage);

        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
    //生成亂數
    public String randomInteger(){
        String random = "";
        for (int i = 0; i < 6; i++) {
            random += (int)(Math.random()*10);
        }
        return random.toString();
    }
}

@PostMapping("/register")
public R register(@RequestBody User user, HttpSession session) {
    String code1 = (String) session.getAttribute("code");
    String email1 = (String) session.getAttribute("email");
    if (!email1.equals(user.getEmail())) {
        return R.error("郵箱錯誤");
    }
    if (!code1.equals(user.getCode())) {
        return R.error("驗證碼錯誤");
    }
    User user1 = new User(user.getEmail(), user.getPassword());
    return service.register(user1);
}