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Subject: RE: Response and file downloads
From: Ben Souther <bsouther@fwdco.com>
To: Tomcat Users List <tomcat-user@jakarta.apache.org>
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	 <86901B49BB9A9F409862F5520B389CED133160@tmc2ksbs.tmc.technical-magic.com>
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Organization: F.W. Davison & Co, Inc.
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Date: Mon, 01 Nov 2004 15:26:33 -0500
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As the other poster correctly stated HTTP is a single request/response
protocol -- emphasis on "protocol".  Once you send the headers and
response to a browser from a server, you can't send another one.
This is not a Tomcat issue.


On Mon, 2004-11-01 at 15:17, Luc Foisy wrote:
> I know there is only a single response, thats why I want to create a new one :)
> 
> I don't even want to get into opening other windows nor do I want to rely on javascript for required operation.
> 
> I am not sure what you are refering to as atypical or robustness...
> 
> How do other sites generate files on the fly (take it out of a database, or a report just run), on form submit, and send them down the line and not run into this problem?
> 
> I see many people posting many places on the net that they are using the response to send a file, a lot of them are getting this IllegalState, but I never really found a followup solution that really fit my needs.
> 
> Why would the possibility exist to push a file through the response if it leaves you with the ability to go nowhere after?
> 
> (not really questions possed to you Justin, just hoping to keep it alive)
> 
> -----Original Message-----
> From: Justin Ruthenbeck [mailto:justinr@nextengine.com]
> Sent: Monday, November 01, 2004 2:56 PM
> To: Tomcat Users List
> Subject: Re: Response and file downloads
> 
> 
> 
> Luc,
> 
> At 11:42 AM 11/1/2004, you wrote:
> >I am having a wee problem with using the response.
> >
> >I have a form on a page, with a submit button to download a file. That 
> >file is being pulled from a database and pushed to the response.
> >The problem I am having, I just used that response to submit the page, 
> >so I am getting and IllegalStateException, even though it is still 
> >pushing the file to the browswer
> >I also want to be able to send a redirect after the file is downloaded 
> >(so I can refresh the page so the form submit page is regenerated, since 
> >we are using a string to determine unique submits are only coming from 
> >the pages we generated, and not the browser address bar)
> >
> >Can we get a new response from the session variable (the one available 
> >to jsp writing) to send the file, then get another new response to 
> >perform a redirect....
> >Basically I want to be able to do something like
> >
> >the form submits, and passes to the applications perform methods through 
> >the jsp catching the submit
> >response = new Response
> >response.sendFile
> >response = new Response
> >response.sendRedirect
> >(yes I know those are not actual methods and classes, just trying to 
> >explain what I want)
> 
> Your understanding of how, exactly, the http protocol works is 
> incorrect.  Because it is a (single) request, (single) response protocol, 
> what you're asking for cannot be done.
> 
> It seems like what you want is for a user to fill out a form, click 
> submit, then be presented with a new, fresh, form again ... with the file 
> download on the side.  If you have determined that you absolutely want 
> this behavior (it's atypical, so doing it won't be particularly robust), 
> consider programmatically opening another browser window on form submit 
> from which the download will happen ... and reload your form in your 
> "main" browser window.  This will, of course, subject you to any 
> headaches associated with javascipt window opening.
> 
> justin
> 
> 
> 
> ______________________________________________
> Justin Ruthenbeck
> Lead Software Engineer, NextEngine Inc.
> justinr - AT - nextengine DOT com
> Confidential. See:
> http://www.nextengine.com/confidentiality.php
> ______________________________________________
> 
> 
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