Re: Image cache problem - solved

[Adam Hardy]

Struts 1.1 will do this for you automatically if you set the following 
in your struts-config.xml

<controller>
    <!-- all pages get HTTP headers to defeat browser caching -->
    <set-property property="nocache" value="true"/>
  </controller>
David Bolsover wrote:
Remke

Thanks

I was already setting:
response.setHeader("Cache-Control","no-cache");
response.setHeader("Pragma","no-cache");
In the jsp containing the image to solve the problem of page caches.
What caught me out was that this had to do this for the image also - as I had
just done before your mail came in!
In my createimageAction I now have:

OutputStream sos = response.getOutputStream();
response.setHeader("Cache-Control","no-cache");
response.setHeader("Pragma","no-cache");
response.setContentType("image/jpeg");
.... write image to sos
sos.close();
....
return null;
Problem solved :-)

David



-----Original Message-----
From: Remke Rutgers [mailto:[EMAIL PROTECTED]
Sent: 19 June 2003 13:24
To: 'Struts Users Mailing List'
Subject: RE: Image cache problem
Hi David,

I think it has nothing to do with browser versions, I think this is only
caused by caching settings. You must realize that caching can occur both in
browser cache (configure this using Tools->Internet
Options->General->Temporary Internet Files->Settings) and in proxy server
cache. You should force your createimage.do to be non cachable. (Instruct
proxy servers and browsers to always retrieve a fresh version)
You can achieve this by setting a HTTP header:
response.setHeader("Cache-Control","no-cache");
see the javadocs for more on the setHeader method of the response object.
See http://www.mnot.net/cache_docs/ for a very good tutorial on caching.

Remke

-----Oorspronkelijk bericht-----
Van: David Bolsover [mailto:[EMAIL PROTECTED]
Verzonden: donderdag 19 juni 2003 13:51
Aan: Struts User
Onderwerp: Image cache problem
Hi all

I have been using struts for some time now but a new problem has come up:

I use a form to select some options needed retrieve some data required to
generate a graph.
For the sake of clarity, I'll call this retrieveDataAction.

retrieveDataAction gets the data and places it into session scope under key
'GRAPHDATA' the user is then forwarded to displaydata.jsp.
displaydata.jsp contains the following (simplfied):

<logic:present name="GRAPHDATA" scope="session" >

<p><html:img page="/createimage.do" /></p>

</logic:present>

The createimageAction retrieves the GRAPHDATA from session scope, generates
a
gif image and writes it to response.OutputStream(), closes the stream and
returns null.
The problem I have is that at least one client (using IE 5) finds that the
same
image is always presented even though he has requested some different data.
I
have not been able to reproduce the problem using an IE 6 client - does
anyone
know if this is an IE 5 'feature' and - is there a solution?
David Bolsover

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