邮件发送案例流的形式文件不落盘

可以实际使用的

  public static void main(String[] args) {
        // 身份认证
        Session session = authorUser();
        // 收件人电子邮箱
        String from = "邮箱";
        // 发件人电子邮箱
        String to = "邮箱";
        send2User(session, from, to);
    }

    private static Session authorUser() {
        // 获取系统属性
        Properties properties = System.getProperties();
        // 指定发送邮件的主机为 localhost
        String host = "xamail.byd.com";
        // 设置邮件服务器
        properties.setProperty("mail.smtp.host", host);
        properties.put("mail.smtp.port", "25");
        properties.put("mail.smtp.auth", "true");
        // 判断是否需要身份认证 如果需要身份认证，则创建一个密码验证器
        MailAuthenticator authenticator = new MailAuthenticator("邮箱", "123@123");
        // 根据邮件会话属性和密码验证器构造一个发送邮件的session
        Session session = Session.getDefaultInstance(properties, authenticator);
        return session;
    }

    private static void send2User(Session session, String from, String to) {
        try {
            // 创建默认的 MimeMessage 对象
            Message message = new MimeMessage(session);
            // Set From: 头部头字段
            message.setFrom(new InternetAddress(from));
            // Set To: 头部头字段
            message.addRecipient(Message.RecipientType.TO,
                    new InternetAddress(to));
            // Set Subject: 头部头字段
            message.setSubject("某项目数据20240822");
            // Create a multipar message
            Multipart multipart = new MimeMultipart();
            // Create the message part
            BodyPart messageBodyPart = new MimeBodyPart();
            // Fill the message
            messageBodyPart.setText("Message test bym!!!");
            // Set text message part
            multipart.addBodyPart(messageBodyPart);

            // Part two is attachment 附件发送
            messageBodyPart = new MimeBodyPart();

//            方式一发送附件为文件的形式
//            String filename = "D:\\test\\test.txt";
 //            DataSource source = new FileDataSource(filename);
//            messageBodyPart.setDataHandler(new DataHandler(source));
//            messageBodyPart.setFileName("test.txt");

//            方式二、发送附件为流的形式，好处：数据直接查询出来，不落文件
            List<List<String>> head = head();
            List<List<Object>> lists = dataList();
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            EasyExcel.write(bos).sheet("sheet1").head(head).doWrite(lists);
            byte[] array = bos.toByteArray();
            ByteArrayDataSource byteArrayDataSource = new ByteArrayDataSource(array, "application/octet-stream");
            messageBodyPart.setDataHandler(new DataHandler(byteArrayDataSource));
            messageBodyPart.setFileName("test.xlsx");


            multipart.addBodyPart(messageBodyPart);

            // Send the complete message parts
            message.setContent(multipart);
            // 发送消息
            Transport.send(message);
            System.out.println("Sent message successfully....");
        } catch (MessagingException mex) {
            mex.printStackTrace();
        }
    }


    private static List<List<String>> head() {
        List<List<String>> list = com.alibaba.excel.util.ListUtils.newArrayList();
        List<String> head0 = com.alibaba.excel.util.ListUtils.newArrayList();
        head0.add("字符串" + System.currentTimeMillis());
        List<String> head1 = com.alibaba.excel.util.ListUtils.newArrayList();
        head1.add("数字" + System.currentTimeMillis());
        List<String> head2 = com.alibaba.excel.util.ListUtils.newArrayList();
        head2.add("日期" + System.currentTimeMillis());
        list.add(head0);
        list.add(head1);
        list.add(head2);
        return list;
    }

    private static List<List<Object>> dataList() {
        List<List<Object>> list = com.alibaba.excel.util.ListUtils.newArrayList();
        for (int i = 0; i < 10; i++) {
            List<Object> data = com.alibaba.excel.util.ListUtils.newArrayList();
            data.add("字符串" + i);
            data.add(0.56);
            data.add(new Date());
            list.add(data);
        }
        return list;
    }