Why there are many framework support multiple uploads, but none for multiple downloads?

If I am not wrong, multiple download can only accomplish by zipping file together. What so special abou开发者_如何转开发t multiple download compare to multiple upload?

Here's something interesting you may want to read: http://www.motobit.com/tips/detpg_multiple-files-one-request/

Essentially, conventional browsers expect one file+ContentType in the HTTP response. Although most current browsers may accept a multipart response, YMMV. From what I can see of the examples, the format is pretty similar (maybe identical) to sending an email with multiple attachments.

Multipart Responses in HTTP

Note that the link in the other answer also explains this practice, it's just a little farther down on the page.