在base64中附加javamail中的大文件

File file = new File("path/to/file");
byte[] fileBytes = new byte[(int) file.length()];
try (FileInputStream fis = new FileInputStream(file)) {
    fis.read(fileBytes);
} catch (IOException e) {
    e.printStackTrace();
}

String base64EncodedFile = Base64.getEncoder().encodeToString(fileBytes);

Properties properties = new Properties();
properties.put("mail.smtp.host", "smtp.example.com");
Session session = Session.getInstance(properties);

MimeMessage message = new MimeMessage(session);
message.setFrom(new InternetAddress("sender@example.com"));
message.setRecipient(Message.RecipientType.TO, new InternetAddress("recipient@example.com"));
message.setSubject("Attachment Test");

// 创建一个Multipart对象，用于存储邮件的各个部分
Multipart multipart = new MimeMultipart();

// 创建一个MimeBodyPart对象，用于存储文本内容
MimeBodyPart textPart = new MimeBodyPart();
textPart.setText("This is the message body.");

// 将文本内容添加到Multipart对象中
multipart.addBodyPart(textPart);

// 创建一个MimeBodyPart对象，用于存储附件
MimeBodyPart attachmentPart = new MimeBodyPart();
attachmentPart.setFileName("filename.txt");
attachmentPart.setContent(base64EncodedFile, "application/octet-stream");

// 将附件添加到Multipart对象中
multipart.addBodyPart(attachmentPart);

// 将Multipart对象设置为邮件的内容
message.setContent(multipart);

// 发送邮件
Transport.send(message);