javax.mail : Get nested attachments in EML attachment

Question

我有一个现有代码可以正确下载和处理一些电子邮件。

要处理的电子邮件必须有一个或多个 xml 作为附件，现在我正在迁移这个过程从当前的标准邮件帐户到一个认证系统，该系统将邮件包装到一个新的电子邮件。

因此，我必须解析一封带有 XML(经过认证)和 EML(我应该处理的消息)的电子邮件，而不是带有一个 xml 附件的平面电子邮件。

简而言之，我的代码如下:

private void processMessage(final Message message) {
    try {
        final String contentType = message.getContentType();
        if (contentType.contains("multipart")) {
            final Multipart multiPart = (Multipart) message.getContent();

            for (int i = 0; i < multiPart.getCount(); i++) {
                final MimeBodyPart part = (MimeBodyPart) multiPart.getBodyPart(i);

                /**************************************************************
                 * HERE I CAN'T GET THE EML (and its attachments) FROM 'part' *
                 **************************************************************/

                if (Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition())) {
                    processAttachment(part);
                }
            }
        }
    } [...cutted...]
}

private void processAttachment(final MimeBodyPart part) throws IOException, MessagingException {
    final InputStream input = getReusableInputStream(part);

    if (part.getFileName() != null && isXmlType(part.getContentType())) {
        processXml(input);
    }
}

我应该修改它，以便解析 EML 并递归地获取附件，但我错过了全局。

更新:我已经修改了processAttachment 方法(但它仍然不起作用):

private void processAttachment(final Multipart multipart) {

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

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

            System.out.println("Filename: " + bodyPart.getFileName());
            System.out.println("ct: " + bodyPart.getContentType());

            final boolean isXml = bodyPart.getFileName() != null && isXmlType(bodyPart.getContentType());
            if (isXml) {
                final InputStream inputStream = getReusableInputStream(bodyPart);
                processXMLAttachment(inputStream);
            }

        }
    } [cutted]

}

输出是:

Filename: null
ct: TEXT/PLAIN; charset=iso-8859-1
Filename: null
ct: TEXT/HTML; charset=iso-8859-1
Filename: daticert.xml
ct: APPLICATION/XML; name=daticert.xml
Filename: postacert.eml
ct: MESSAGE/RFC822; name=postacert.eml
Filename: smime.p7s
ct: APPLICATION/X-PKCS7-SIGNATURE; name=smime.p7s

从输出中，我可以看到系统只扫描了第一级附件 daticert.xml 和 postacert.eml 但没有找到嵌套附件。

更具体地说，我必须阅读以下内容:

Filename: postacert.eml
ct: MESSAGE/RFC822; name=postacert.eml

有什么帮助吗？

谢谢

Answer 1

好吧，我通过检查任何 MimePart 的类来解决，我发现嵌套消息是 IMAPNestedMessage 的类型，所以在这种对象上我递归调用主要方法processMessage:

private void processAttachment(final Multipart multipart) {

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

// BEGIN - Added this part
            System.out.println("CLASS bodyPart: " + bodyPart.getContent().getClass());

            if (bodyPart.getContent() instanceof IMAPNestedMessage) {
                processMessage((IMAPNestedMessage) bodyPart.getContent());
            } else {
// END - Added this part
                if (bodyPart.getContent() instanceof Multipart) {
                    processAttachment((Multipart) bodyPart.getContent());
                } else {
                    final boolean isXml = bodyPart.getFileName() != null && isXmlType(bodyPart.getContentType());
                    if (isXml) {
                        final InputStream inputStream = getReusableInputStream(bodyPart);
                        processXMLAttachment(inputStream);
                    }
                }
            }

        }
    } catch (final Exception e) {
        sendMailService.sendMailForImportINPSFailed("metodo processAttachment()", e);
        e.printStackTrace();
    }

}

现在它工作正常。