java - 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 receives the multipart content, parses it etc. Obviously, at every moment I know the number of bytes received so far. However in order to supply an info for the progress bar on the client side a servlet also needs the total number of bytes for the file, which is being uploaded. Any idea where to get the total number of bytes from please?

Thanks!

Answer 1

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 ...