前期工作

1. 准备一个可以发邮件的邮箱，这里选择的是qq邮箱
2. 点击设置

3. 点击账户

4. 点击开启（我已经是开启了）

5. 按照提示步骤，获取授权码，记得保存好授权码

springboot

1. pom.xml

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

2. 配置文件

  spring：
      mail:
        host: smtp.qq.com
        port: 587
        username: 你的邮箱地址
        password: 刚才生成的授权码
        default-encoding: utf-8

3. service层

package com.example.monitorserver.service.Impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.example.monitorserver.mapper.ProjectMapper;
import com.example.monitorserver.mapper.UserMapper;
import com.example.monitorserver.mapper.UserProjectMapper;
import com.example.monitorserver.po.Project;
import com.example.monitorserver.po.User;
import com.example.monitorserver.po.UserProject;
import com.example.monitorserver.service.SendEmailService;
import lombok.extern.slf4j.Slf4j;
import org.hibernate.validator.constraints.pl.REGON;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.mail.MailException;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSenderImpl;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.LinkedList;
import java.util.List;

@Service
@Slf4j
public class SendEmailServiceImpl implements SendEmailService {
    @Autowired
    private JavaMailSenderImpl mailSender;

    @Resource
    private UserProjectMapper userProjectMapper;

    @Resource
    private ProjectMapper projectMapper;

    @Resource
    private UserMapper userMapper;

    //注入发件人地址【这里获取的是全局配置里的username】

    @Value("${spring.mail.username}")
    private String from;

    @Override
    public void sendSimpleEmail(String subject, String text,String email) {
        SimpleMailMessage message = new SimpleMailMessage();

        message.setFrom(from);

        //发送的对象
        message.setTo(email);

        //标题
        message.setSubject(subject);

        //内容
        message.setText(text);

        //发送
        sendEmail(message);

        return true;
    }

    private void sendEmail(SimpleMailMessage message) {
        try {
            mailSender.send(message);
            log.debug("邮件发送成功");
        } catch (MailException e) {
            log.debug("邮件发送失败");
            e.printStackTrace();
        }
    }
}