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From Peter Courcoux <pe...@courcoux.biz>
Subject Re: [Fileupload] Progress bar
Date Tue, 23 Dec 2003 21:11:10 GMT
Hi Eric,

My implementation using turbine is a bit more complex than this but this
should give you the idea :-

1.	Populate the VelocityContext of the page containing the fileupload
form with a uniqueid to a cached reference to a new instance of a
ProgressReporter object. This is done in the page setup using a turbine
pulltool. 

2. 	I use a time expired cache so that if something goes wrong the cache
cleans up after itself.

3.	Add the unique id to the upload form using a known parameter name.

4.	Add a javascript onClick handler to the form to open a new upload
status window. Pass the unique id to the window.

5.	On form submission, the ParameterParser(request parser) reads the
unique id for the ProgressReporter obtained at 1. It uses this to obtain
the referenced object from the cache and passes this to the upload
service which updates it as the request is read. 

6.	The upload status window uses the same uniqueid it was given at point
4 and again using a pull tool queries the server for the
ProgressReporter object and displays the result. The UploadStatus window
is set to reload every 5 seconds and consequently displays the updated
status. When the ProgressReporter object is released when the request is
completely read, the window is set to close, again using javascript.

This has been working for 7 or 8 months now very successfully.

The server on which this is used regularly receives uploads from a few
Kb to an average of 20MB and occasionally up to its limit of 100MB.
Rather than implement a progress bar, I report the size of the request,
the bytes read and the name of the file object currently being
processed. It would, of course be relatively easy to take this
information and produce a progress bar.

Does this make sense?

I intend to post a detailed set of examples and instructions on the
turbine site (In fact I produced a draft in May or June but I'll have to
review it all again), but only when I have the support in
commons-fileupload. It's no good to anyone until then!

Regards,

Peter


On Tue, 2003-12-23 at 20:29, Eric H. Jung wrote:
> Sorry for not replying to the thread started by Eric Pugh at
> http://www.mail-archive.com/commons-dev%40jakarta.apache.org/msg32368.html,
> but I've only just joined commons-dev as suggested to me by Yoav on
> tomcat-dev.
> We were discussing a related topic there.
> 
> I've gone through signifcant efforts to extend commons-fileupload using
> Listener interfaces
> in order to support a progress bar to no avail. I researched what others
> have done,
> including but not limited to
> http://www.javazoom.net/jzservlets/uploadbean/uploadbean.html
> (which, by the way, seems to redistribute commons-fileupload without any
> mention of Apache).
> 
> I do not see how this problem can be tackled without writing one's own (or
> extending another)
> servlet container. There is currently no way in the servlet spec to know the
> number of bytes
> that have been read as a ServletRequest is being processed. By the time
> Servlet.service() or
> Filter.doFilter() are called, the *entire* InputStream has been read from
> the socket, leaving no
> way to provide user feedback during the upload.
> 
> I could be totally off base here, and if I am, I'd appreciate it if someone
> would show me the light.
> 
> Thank you,
> Eric H. Jung
> ejung@russellmellon.com
> 
> 
> 
> 
> 
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-- 
Peter Courcoux <peter@courcoux.biz>

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