how to download an attachment in browser? - gmail-api

Question

I'm using the Gmail API in browser and want to allow the user to download email attachments. I see https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get but it returns JSON and base64 data. I don't think I can get that data in memory then trigger a "download" to save the file locally. Even if I could I don't think it would be efficient - it would probably download the file in memory vs. streaming it to a file. I think I need a direct link to a file that returns the correct file name and raw binary data (not base64). Is there a way to do this? Right now the only way I see is to proxy requests.

Answer 1

You can get the data from the base64 and save it to file locally.
If you are getting the attachment in Java, you can use the FileOutputStream class (or f.write() in Python) to write the bytes to file and save it locally with a path.
You can try with the following sample code from Google Developer page:
public static void getAttachments(Gmail service, String userId, String messageId)
throws IOException {
Message message = service.users().messages().get(userId, messageId).execute();
List<MessagePart> parts = message.getPayload().getParts();
for (MessagePart part : parts) {
if (part.getFilename() != null && part.getFilename().length() > 0) {
String filename = part.getFilename();
String attId = part.getBody().getAttachmentId();
MessagePartBody attachPart = service.users().messages().attachment().
get(userId, messageId, attId).execute();
byte[] fileByteArray = Base64.decodeBase64(attachPart.getData());
FileOutputStream fileOutFile =
new FileOutputStream("directory_to_store_attachments" + filename);
fileOutFile.write(fileByteArray);
fileOutFile.close();
}
}
}