使用 Java 提取内联电子邮件附件

Question

我正在使用以下 Java 代码来尝试提取电子邮件附件：

private static List<File> extractAttachment(Message message) {
    List<File> attachments = new ArrayList<File>();
    try {
        Multipart multipart = (Multipart) message.getContent();

        for (int i = 0; i < multipart.getCount(); i++) {
        BodyPart bodyPart = multipart.getBodyPart(i);
        System.out.println("bodyPart.getDisposition(): " + bodyPart.getDisposition());
        if (!Part.ATTACHMENT.equalsIgnoreCase(bodyPart.getDisposition())) {
            continue; // dealing with attachments only
        }
        InputStream is = bodyPart.getInputStream();
        String filePath = "/tmp/" + bodyPart.getFileName();
        System.out.println("Saving: " + filePath);
        File f = new File(filePath);
        FileOutputStream fos = new FileOutputStream(f);
        byte[] buf = new byte[4096];
        int bytesRead;
        while ((bytesRead = is.read(buf)) != -1) {
            fos.write(buf, 0, bytesRead);
        }
        fos.close();
        attachments.add(f);
        }
    } catch (IOException | MessagingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return attachments;
 }

然而，我总是bodyPart.getDisposition(): null。任何线索我应该如何提取内联附件？

谢谢

P.S.: 我在 Mac 上使用 Apple Mail 客户端发送带附件的测试电子邮件。然而，电子邮件客户端不应该受到关注。

Answer 1

我明白了，确实我需要一些 "recursion" 并检查嵌套内容并检查 Part.INLINE.equalsIgnoreCase(bodyPart.getDisposition()。

下面是代码，认为对某人有用：

private static List<File> extractAttachment(Multipart multipart) {
    List<File> attachments = new ArrayList<File>();
    try {

        for (int i = 0; i < multipart.getCount(); i++) {
        BodyPart bodyPart = multipart.getBodyPart(i);

        if (bodyPart.getContent() instanceof Multipart) {
            // part-within-a-part, do some recursion...
            extractAttachment((Multipart) bodyPart.getContent());
        }

        System.out.println("bodyPart.getDisposition(): " + bodyPart.getDisposition());
        if (!Part.INLINE.equalsIgnoreCase(bodyPart.getDisposition())) {
            continue; // dealing with attachments only
        }

        InputStream is = bodyPart.getInputStream();
        String filePath = "/tmp/" + bodyPart.getFileName();
        System.out.println("Saving: " + filePath);
        File f = new File(filePath);
        FileOutputStream fos = new FileOutputStream(f);
        byte[] buf = new byte[4096];
        int bytesRead;
        while ((bytesRead = is.read(buf)) != -1) {
            fos.write(buf, 0, bytesRead);
        }
        fos.close();
        attachments.add(f);
        }
    } catch (IOException | MessagingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return attachments;
    }

Answer 2

当从 mac 发送的消息没有正文内容但附件时，我遇到了类似的问题，在迭代初始消息内容时附件没有显示，并且还必须递归地找到。

我在下面发布了对我有用的内容。

private Map<String, String> extractAttachments(Multipart multiPart, Map<String, String> attachmentAndName) {
    try {
        for (int i = 0; i < multiPart.getCount(); i++) {
            BodyPart part = multiPart.getBodyPart(i);
            if (part.getContent() instanceof Multipart) {
                attachmentAndName = extractAttachments((Multipart) part.getContent(), attachmentAndName);
            } else if (part instanceof MimeBodyPart) {
                MimeBodyPart mimeBodyPart = (MimeBodyPart) part;
                String fileName = createUniqueFileName(mimeBodyPart.getFileName());
                if (Part.ATTACHMENT.equalsIgnoreCase(mimeBodyPart.getDisposition())) {
                    String attachmentAsString = IOUtils.toString(mimeBodyPart.getInputStream(), StandardCharsets.UTF_8);
                    attachmentAndName.put(fileName, attachmentAsString);
                    if (SAVE_ATTACHMENTS_LOCALLY) {
                        saveFile(mimeBodyPart, fileName);
                    }
                }
            }
        }
    } catch (IOException | MessagingException e) {
        logger.error("Failed to process attachment. Continuing to process other message parts in search of attachments...");
    }
    return attachmentAndName;
}

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