一、添加依赖

Maven依赖：

<!--QQ邮箱验证码所需jar包-->
 <dependency>
     <groupId>org.apache.commons</groupId>
     <artifactId>commons-email</artifactId>
     <version>1.5</version>
 </dependency>
<!--     使用redis缓存验证码时效-->
  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-redis</artifactId>
  </dependency>

二、开启QQ邮箱服务

三、配置yml文件

spring:
    redis:
            database: 1
            # redis服务器地址
               host: host
            port: 6379
            # redis服务器密码
            password: password

四、创建SendMail工具类

public static void sendEmailCode(String targetEmail, String authCode) {
        // 设置邮件服务器
        String host = "smtp.qq.com";
        final String username = "xxx";  // 你的QQ邮箱
        final String password = "xxx";  // 你的QQ邮箱密码或应用专用密码
        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", host);
        props.put("mail.smtp.port", "587");
        // 获取默认session对象
        Session session = Session.getInstance(props,
                new javax.mail.Authenticator() {
                    protected PasswordAuthentication getPasswordAuthentication() {
                        return new PasswordAuthentication(username, password);
                    }
                });
        try {
            // 创建默认的 MimeMessage 对象
            Message message = new MimeMessage(session);
            // Set From: 头部头字段 of the header
            message.setFrom(new InternetAddress(username));
            // Set To: 头部头字段 of the header
            message.setRecipients(Message.RecipientType.TO,
                    InternetAddress.parse(targetEmail));
            // Set Subject: 头部头字段
            message.setSubject("注册验证码");
            // 设置消息体
            message.setText("您的验证码是: " + authCode);
            // 发送消息
            Transport.send(message);
        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }

五、编写接口

@RestController
public class SendEmail {
 
    @Resource
    private StringRedisTemplate stringRedisTemplate;
 
    @GetMapping("/getCode")
    @ResponseBody
    public String mail(@RequestParam("targetEmail") String targetEmail) {
//        发送前看下是否有已有缓存验证码
        String prefix = "yzm:" + targetEmail;
        String yzm =  stringRedisTemplate.opsForValue().get(prefix);
        if (yzm == null){
            //        随机生成六位验证码
            String authCode = String.valueOf(new Random().nextInt(899999) + 100000);
            System.out.println(authCode);
            SendMailUtil.sendEmailCode(targetEmail, authCode);
            stringRedisTemplate.opsForValue().set(prefix, authCode);
            return "ok";
        }
        return "请勿重新发送";
    }
}

六、测试