android - 在 Android 中使用 Gmail API 发送带附件的电子邮件(execute() 挂起)

Question

只要附件很小，一切似乎都能正常工作。
但是，当我尝试附加更大的文件(例如 7MB)时，Send 的 execute() 方法挂起。
我试图查看文档，如果我理解正确，我应该使用 send API which actually performs upload但是，我没有想好应该在哪里提供这些参数。
这是电子邮件生成方法:

public MimeMessage toMimeMessage(String from, Context context) throws MessagingException {
    Properties props = new Properties();
    Session session = Session.getDefaultInstance(props, null);

    MimeMessage mimeMessage = new MimeMessage(session);

    mimeMessage.setFrom(new InternetAddress(from));
    mimeMessage.addRecipient(javax.mail.Message.RecipientType.TO, new InternetAddress(recipient));
    mimeMessage.setSubject(subject);

    MimeBodyPart mimeBodyText = new MimeBodyPart();
    mimeBodyText.setContent(body, "text/html");
    mimeBodyText.setHeader("Content-Type", "text/plain; charset=\"UTF-8\"");

    Multipart mp = new MimeMultipart();
    mp.addBodyPart(mimeBodyText);

    if (attachments != null && attachments.size() > 0) {
        MimeBodyPart mimeBodyAttachments = new MimeBodyPart();
        for (Uri uri : attachments) {
            String fileName = UriUtils.getFileName(uri, context);
            String mimeType = UriUtils.getMimeType(uri, context);
            Log.d(TAG, "Generating file info, uri=" + uri.getPath() + ", mimeType=" + mimeType);
            FileInputStream is = UriUtils.generateFileInfo(context, uri, mimeType);
            if (is == null) {
                throw new MessagingException("Failed to get file for uri=" + uri.getPath());
            }
            try
            {
                DataSource source = new ByteArrayDataSource(is, mimeType);
                mimeBodyAttachments.setDataHandler(new DataHandler(source));
                mimeBodyAttachments.setFileName(fileName);
                mimeBodyAttachments.setHeader("Content-Type", mimeType + "; name=\"" + fileName + "\"");
            } catch (IOException e) {
                throw new MessagingException(e.getMessage());
            }
        }
        mimeBodyAttachments.setHeader("Content-Transfer-Encoding", "base64");
        mimeBodyAttachments.setDisposition(MimeBodyPart.ATTACHMENT);
        mp.addBodyPart(mimeBodyAttachments);
    }

    mimeMessage.setContent(mp);

    return mimeMessage;
}

.

Message createMessageWithEmail(MimeMessage mimeMessage) throws MessagingException, IOException {
        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
        mimeMessage.writeTo(bytes);
        String encodedEmail = Base64.encodeBase64URLSafeString(bytes.toByteArray());
        Message message = new Message();
        message.setRaw(encodedEmail);
        return message;
    }

其次是:

MimeMessage mimeMessage = email.toMimeMessage(userId, context);
Message message = createMessageWithEmail(mimeMessage);
Gmail.Users.Messages messages = service.users().messages();
Gmail.Users.Messages.Send send = messages.send(userId, message);
send.execute(); // method hangs when using large attachment

Answer 1

如您所述，我认为您达到了允许的消息大小上限。我不认为(如果我错了，请有人纠正我)Java Gmail API 客户端对超过这个大小的邮件有任何内置支持，所以由你来实现它。

在幕后，messages.send 方法产生一个常规的 http POST 请求:

POST https://www.googleapis.com/gmail/v1/users/{USER_ID}/messages/send
Content-Type: application/json
Authorization: Bearer {ACCESS_TOKEN}

{
  "raw": "{MESSAGE_URL_SAFE_BASE64_ENCODED}"
}

正如您发现的那样，这仅适用于总大小约为 5 mb 的情况。如果您想使用 35 mb 的最大限制，您需要执行以下操作:

POST https://www.googleapis.com/upload/gmail/v1/users/{USER_ID}/messages/send?uploadType=multipart
Content-Type: message/rfc822
Authorization: Bearer {ACCESS_TOKEN}

"{MESSAGE_IN_RFC822_FORMAT}"

注意 URL 中的 upload，uploadType=multipart URL 参数，message/rfc822 为 Content-Type 和 未编码的消息 在请求正文中。 This answer可能会有所启发。

因此您可能需要绕过 Java 客户端(同样，如果我错了，请有人纠正我)并使用其他一些库自己发出常规的 http 请求。