XMLHttpRequest caching problem

Hi all,

I am using the XMLHttpRequest object to load static XML files.
My problem is, that XMLHttpRequest generates unconditional GET requests 
(specifying Pragma: no-cache and Cache-Control: no-cache).

Found an earlier post in this group with no answer (appended below).

Please help, and thanks for your time,
Adrian.

Jeremy Hartley wrote:
> I am using xmlhttp to retrieve a very large static xml file. I really 
> want this to be cached, so that the load time of my application is as 
> small as possible, however Mozilla's default HTTP Headers seem to be 
> made to frustrate this effort, by switching off any caching. .
> 
> See the code below and a description of its results for more details.
> ___________________________________________
> 
> xmlhttp = new XMLHttpRequest();
>     
> xmlhttp.open("GET", "huge.xml",true);
> xmlhttp.onreadystatechange=function() {
>     if (xmlhttp.readyState==4) {
>         alert(xmlhttp.responseText);
>     }
> }
> 
> xmlhttp.send(null);
> 
> ________________________________________________
> 
> This code will produce a GET Request with the following HTTP headers: 
> Cache-Control: no-cache
> Pragms: no-cache
> 
> This disables any caching. I don't want this at all. I have tried to 
> override the values using commands like.
> 
>     xmlhttp.setRequestHeader('Cache-Control', '');
>     xmlhttp.setRequestHeader('Pragma', '');
> 
> This has no effect at all.
> 
> Another attempt:
> 
> xmlhttp.setRequestHeader('Cache-Control', 'Hello');
> xmlhttp.setRequestHeader('Pragma', 'Hello');
> 
> Produces the following HTTP Headers:
> Cache-Control: Hello, no-cache
> Pragms: Hello, no-cache
> 
> Which still seems to override any ability to use the caching data.
> 
> If anybody has any useful ideas or explanation for this behavior please 
> don't hesitate to contact me.
> 
> Kind regards,
> 
> Jeremy Hartley