JSP returning PDF

[Chris Faulkner <ch...@ntlworld.com>]

Hi 

I'm using FOP in a JSP to return dynamically created PDF documents to browsers. I'm using the usual method of embedding FOP as described on the web site. It works great. The main problem is that the 
PDFs take about 20 seconds to generate and then, since they are 500K or so, a while to download depending on connection speed. 

I'd like to be able to put a message on an intermediate page which could refresh and only return the PDF when it is ready. At the moment, they are just seeing a blank page until the PDF is complete. Does 
anyone have any ideas for this ? Can I flush some output to the page to advise them to be patient, then reset the response and send the PDF when it is ready?

Alternatively. I was thinking of doing something a bit more ambitious which would be to output the PDF to a database blob, then send back a page which refreshes to a JSP which keeps checking whether 
the PDF has been finished. When it is, I could fetch the data outofthe BLOB and send it back.

I have seen other sites where the PDF was output to a static file on the website. Then the JSP would refresh and keep checking until the file was present. When the file was created, the page would 
appear with a link to the file. The main problem with this is security. There is the potential that everyone would have access to all PDFs on the web site, although on a site without listings, they'd need to be 
making pretty inspired guesses to find and download it.

How do others get around this ? I imagine its quite a common problem.

Thanks


Chris

Re: JSP returning PDF

[Patrick Lanphier <pm...@artemisgroup.com>]

All one really has to do is example in PHP

function stall_browser($records,$file){
  Header("Cache-Control: must-revalidate");
  $minutes = floor(round(($records * .82)/60,2));  //Calulated at .77
  $seconds = (round(($records * .82)/60,2)-$minutes) *60;
  $offset = 60 * 60 * 24 * 0;
  $ExpireString = gmdate("D, d M Y H:i:s", time() + $offset) . " GMT";
  Header("Expires: " . $ExpireString);
  echo "<META HTTP-EQUIV=Expires CONTENT=\"$ExpireString\">";

 {put what you would like to see here on the page}
 {flush}
 {feed a small bitstream until completed}
 for ($i=0;$i<2;$i++) echo str_repeat (' ',512) ."\n";

 {when finished send}
   echo "<div align='center'><a href='http://www.energywatchdog.com/usi/ind
  echo "</body>\n";
  echo "</html>\n";
  echo "<META HTTP-EQUIV=Refresh CONTENT=\"0; URL=http://www.energywatchdo
  exit;
};

The refresh redirect is to the new PDF file.  If you do this any other way
that I have tried it works in some browsers and not others this appears to
work in all broswers.

Patrick Lanphier
The Artemis Group
http://www.artemisgroup.com
phone: 814-235-0444
  fax: 800-582-9710

On Fri, 19 Apr 2002, Chris Faulkner wrote:

> Hi
>
> I'm using FOP in a JSP to return dynamically created PDF documents to browsers. I'm using the usual method of embedding FOP as described on the web site. It works great. The main problem is that the
> PDFs take about 20 seconds to generate and then, since they are 500K or so, a while to download depending on connection speed.
>
> I'd like to be able to put a message on an intermediate page which could refresh and only return the PDF when it is ready. At the moment, they are just seeing a blank page until the PDF is complete. Does
> anyone have any ideas for this ? Can I flush some output to the page to advise them to be patient, then reset the response and send the PDF when it is ready?
>
> Alternatively. I was thinking of doing something a bit more ambitious which would be to output the PDF to a database blob, then send back a page which refreshes to a JSP which keeps checking whether
> the PDF has been finished. When it is, I could fetch the data outofthe BLOB and send it back.
>
> I have seen other sites where the PDF was output to a static file on the website. Then the JSP would refresh and keep checking until the file was present. When the file was created, the page would
> appear with a link to the file. The main problem with this is security. There is the potential that everyone would have access to all PDFs on the web site, although on a site without listings, they'd need to be
> making pretty inspired guesses to find and download it.
>
> How do others get around this ? I imagine its quite a common problem.
>
> Thanks
>
>
> Chris
>
>