I'm not sure I correctly understand the problem anymore, but this might
be relevant:
Can't you let the JPEG servlet indicate that its output should not be
cached? I use this code to disable various cache mechanism:
private void setNoCache(HttpServletResponse resp) {
resp.setHeader("Pragma","No-Cache");
resp.setHeader("Cache-Control","no-Cache");
resp.setDateHeader("Expires", 0 );
}
Regards,
Jeroen
Op 19-1-2006 22:11, schreef Glen Mazza:
Clay Leeds escribió:
On Jan 19, 2006, at 10:30 AM, Glen Mazza wrote:
Jeremias Maerki wrote:
Or you need to simply make sure that the URLs are unique. You can
use a
dummy parameter in the URL to fake uniqueness:
http://localhost/MyChartServlet?dummy=1234
Hmmm...my guess is that for any servlet-related problem for which a
"dummy parameter to fake uniqueness" would solve it, that the
servlet itself can be rewritten to fix the problem instead. (In
this case, have it coded to regenerate the image for every call,
with no dummy parameter needed.) If I'm correct, I would refer the
questioner to the Sun Servlet forum for more assistance.
Glen
In my experience (mainly coming from a background where the user-
agent tends to be a web browser), if you call the same thing twice,
there are a number of places where the object being served can be
'cached':
- server
- proxy
- client
Oh. My interpretation of the problem was that a different PDF
document *was* indeed being returned each time, but that the charts
within the PDF document were incorrectly not being regenerated to
account for the new data specific to each document. If my assumption
was the case, that would tend to rule out caching at the client or the
proxy, because AFAIK they would just have a PDF document to cache (not
inner parts, such a graphics within the PDF).
But if it is the case that the *same* PDF document is being sent each
time to the browser, then yes, the caching may be at the client or
proxy-level, and the URL modifying may be necessary.
Glen
In some cases, the server itself also might have some sort of
'caching' system as well, which is external to the server.
If someone is calling a cacheable resource, I've found it safest to
somehow modify the name (even slightly) to ensure there's no caching
involved. IMO, this alleviates the potential of cacheability (making
words up can be fun!).
Web Maestro Clay
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