I am trying to rely upon the browser cache to hold
JSON data returned from AJAX calls in jQuery.
Normal browser activity relies upon the browser cache all the time.
Example: jpg and gif images are not refetched on a page reload.
But when I try using jQuery getJSON ajax calls, I cannot seem to avoid fetching the data from the server.
My returned headers look like this (confirmed with firebug):
Transfer-Encoding: chunked
Date: Wed, 05 Aug 2009 02:55:39 GMT
Content-Type: text/plain; charset=ISO-8859-1
Expires: Wed, 05 Aug 2009 03:55:39 GMT
Cache-Control: max-age=3600
Yet an immediate refresh of the page causes identical requests to hit the server.
I've seen several postings about avoiding caching behavior, which isn't what I need.
I've seen several postings about utilizing caching, but those all seem to rely
upon saving data in the DOM. I want something that behaves just like cached images do during a page reload.
Cant the browser just fetch it from it's own cache?
--x--x--x--x UPDATE --x--x--x--
Much to my disappointment, several respectable folks agree that this isn't just possible.
Some even argue that it shouldn't be (which still baffles me).
Stubburn to a fault, I tried the following:
I set the Etag header on all outgoing pages I want to be cached
(I pick a few choice URL arguments that represent the data I'm requesting and just use that for the Etag value)
At the beginning of the next request, I simply check if the 'If-None-Match' header is in the request. If so, then the browser isn't caching the request like I wanted, so I sent a 304 Not Modified response.
Testing shows that Firefox won't cache my request
(but I can still avoid the 'fetch the expensive data' part of my cgi),
while IE6 will actually cache it (and wont even attempt fetching back from the server).
It's not a pretty answer, but it's working for me for now
(those pesty full-page refreshes of graph data wont be so slow or expensive now).
(What? I'm running IE6! OMG! Oh look a squirrel!)
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