> -----Original Message-----
> From: Simon Hook [mailto:simon.j.hook@xxxxxxxxxxxx]
> Sent: Donnerstag, 10. März 2005 07:23
> To: users@xxxxxxxxxxxxxxxx
> Subject: [users@httpd] When an image is replaced in the
> htdocs directory
> through a cgi script and incorporated into a new html page
> the new image
> does not get incorporated.
>
>
> PROBLEM: When an image is replaced in the htdocs directory
> through a cgi
> script and incorporated into a new html page the new image
> does not get
> incorporated.
>
> Hi All,
>
> I am trying to write a web app where a variable, passed with
> a form, is
> used to generate a plot, which is saved and then displayed
> as a static
> image in an html page. I am using the webform from pythonweb and
> generating the plot with matplotlib. I am using Apache 2.053 under
> Windows XP. I am keeping it real simple by simply passing an integer.
> The whole process works, HOWEVER, when I back page and submit a new
> integer value which generates a new plot and new static
> image, the new
> image does not get displayed, instead the last version of the static
> image (plot) is displayed (presumably from the cache).
Rather, "...presumably from *a* cache..."
There are several points where data are cached in a typical
browser-server configuration:
- in the server: Are you using mod_cache? If so, try CacheDisable the
path to the cgi, or just switch off (don't Load it).
- in the network: Are the browser and server connected via a network? If
there are proxies in the route, they will certainly cache things.. Can
you connect directly?
- in the browser: disable caching (thought his will make pages slow to
load - it'll have to reload images every time
To check if it's really the server, use a browser with caching turned
off and connected directly to the server..
Rgds,
Owen Boyle
Disclaimer: Any disclaimer attached to this message may be ignored.
> If I
> reload the
> page with the browser the updated image gets displayed otherwise the
> previous plot gets displayed with 2 or 3 re-submits and then
> eventually
> an updated one is displayed. It seems like Apache does not
> recognize a
> changed image and still uses the first plot I created for 2
> or 3 submits
> or the submit does not force Apache to look for a changed file.
>
> I am new to Apache, Pythonweb and MatplotLib although I have done
> similar stuff with ASP and IIS and some Python work. I have waded
> through the Apache and Pythonweb documentation and got
> nowhere. I have
> tried using the MOD_EXPIRES directive with Apache but this has no
> effect. I think this is because a new image (PNG) has been generated
> rather than an old one has expired. I cannot see any way with
> pythonweb
> forms to load a static html page (i.e. with cgi). I think if I had a
> static html page I could write out maybe I could expire that
> which would
> force Apache to load the new image file.
>
> I have tried
>
> <META HTTP-EQUIV=Refresh CONTENT=1>
>
> which refreshes the page every second - this works but who
> would want it!
>
> I have tried
>
> <META HTTP-EQUIV=expires CONTENT=0>
>
> but this does not work.
>
> I have attached the code below, its a rework of one of the
> examples in
> pythonweb. Just copy this to the cgi-bin directory and it
> should work,
> provided matplotlib is installed. Matplotlib is available from:
>
> http://matplotlib.sourceforge.net/
>
> Pythonweb is available from:
>
> http://www.pythonweb.org
>
> Despite hours of trying I cannot get this to work, which
> would seem like
> a necessity for Pythonweb and Apache. Any help would be much
> appreciated.
>
> Thanks,
>
> Simon
>
> ---cut here
>
> #!d:/apps/Python23/python
>
> "The form that will not update"
>
> import sys, re, os
> sys.path.append('../')
> sys.path.append('../../')
>
> import web.error; web.error.handle(handler='browser', output='debug',
> format='html')
> import web, web.form, web.form.field.basic, web.util
> import web.form.field.typed
> from pylab import *
>
> class ExampleForm(web.form.Form):
>
> def setup(self):
> self.addField(web.form.field.typed.Integer('myval',
> default=6,
> required=True))
>
> # The preffered way of adding submit buttons is as actions so
> Submit buttons are normally not used.
> self.addAction('Validate This Form')
>
> # Print the HTTP Header
> print web.header('text/html')
>
> # Create a form
> exampleForm = ExampleForm('form', os.environ['SCRIPT_NAME'], 'get')
>
> if len(web.cgi) > 0: # Form submitted
> # Populate form with the values from get.
>
> # Populate the form
> exampleForm.populate(web.cgi)
>
> # Process the form (Validate)
> if exampleForm.valid():
>
> # Grab the desired value, from the form
> myval=exampleForm['myval'].value
>
> # Create the plot, saved as a png in the htdocs directory
> myarray=[myval,4,9,16]
> print myarray
> plot([1,2,3,4], myarray, 'ro')
> axis([0, 6, 0, 20])
> savefig('../htdocs/plot.png')
>
> print "<hmtl><body><div align=center><img src=/plot.png
> alt=theplot></div></body></html>"
>
> else:
> print
> "<html><head><title>noupdate</title></head><body>\n<h1>Input
> integer 0-10</h1>%s\n<hr></body></html>"%(exampleForm.html())
>
> ---end cut
>
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