How to know the file size when uploading via multipart form-data?

Question

I am exercising a simple application with HTML client that uploads a file to the server and must display a progress bar :)

The server is servlet-based, some servlet

Answer 1

Size of content are placed in Content-Length header (see rfc2616). In Servlet you can get this header's value by request.getContentLength() or reqest.getHeaders("Content-Length")

Answer 2

I think you have to implement the progress bar in javascript on the client side.

Anyway, this link gives an explanation of how to do it using JQuery.

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The server can obtain the size of the multipart being uploaded from the HTTP request header; see @ilya's answer. However, getting that information and the count(s) of bytes read so far into a stream of HTTP responses that display or update a progress bar would be rather complicated ...