我试图通过javamail和imap从我的电子邮件下载所有新的电子邮件附件。这一切都很好，但有些附件在PDF中被解码为BASE64，这是我的声明

if (msg.getContent() instanceof Multipart) 

如何获取此附件并将其下载到硬盘？

到目前为止已经尝试过了，第一个IF语句使用Base64解码捕获附件。

for (Message msg : messages) {
        Address[] fromAddress = msg.getFrom();
        String from = fromAddress[0].toString();
        String subject = msg.getSubject();
        String sentDate = msg.getSentDate().toString();

        String messageContent = "";
        String attachFiles = "";

        System.out.println(msg.getContent());


        if (msg.getContent() instanceof BASE64DecoderStream)
        {
            BASE64DecoderStream base64DecoderStream = (BASE64DecoderStream) msg.getContent();
            byte[] byteArray = IOUtils.toByteArray(base64DecoderStream);
        }
        if (msg.getContent() instanceof Multipart) {


            Multipart multipart = (Multipart) msg.getContent();

            for (int i = 0; i < multipart.getCount(); i++) {
                Part part = multipart.getBodyPart(i);
                String disposition = part.getDisposition();

                if ((disposition != null) &&
                        ((disposition.equalsIgnoreCase(Part.ATTACHMENT) ||
                                (disposition.equalsIgnoreCase(Part.INLINE))))) {
                    MimeBodyPart mimeBodyPart = (MimeBodyPart) part;
                    String fileName = mimeBodyPart.getFileName();
                    attachFiles += fileName;
                    File fileToSave = new File(fileName);
                    mimeBodyPart.saveFile(saveDirectory + File.separator + fileToSave);
                    System.out.println("saved attachment: " + fileName + " to disk at: " + saveDirectory);
                }
            }
        }
        System.out.println("\t From: " + from);
        System.out.println("\t Subject: " + subject);
        System.out.println("\t Sent Date: " + sentDate);
        System.out.println("\t Attachments: " + attachFiles);
        System.out.println("");
    }
}

如果有一种简单易行的方法可以将附件下载到我的磁盘，也可以使用NodeJS。尝试过node-imap，但我在那里遇到了同样的错误。