On 17 jan, 10:17, Gabor Szokoli <[email protected]> wrote:
> Hi,
>
> GWT has sheltered us from browser- and javascript intricacies so far
> so well, my questions are probably laughably clueless, so just point
> me to the relevant literature:
>
> We use simple HTTPRequests to get JSON data from the same origin. (not 
> GWT-RPC)
> The browser is supposed to adhere to cache retention directives
> supplied by the server in the response, which is great 99% of the
> time, but then there's always the odd 1%...
> Can my GWT application invalidate elements/subtrees of this cache
> programatically? Think of an in-application "refresh" button, which
> does not reload the GWT client or disturb application state.

The theory says that you should be able to add a "Cache-Control: no-
cache" to your *request*.
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9
That's the theory, I haven't ever tested it...
There's also the conditional-GETs way, using If-Modified-Since, If-
None-Match and similar request headers. Again, that's the theory; your
server should be prepared to served such conditional requests in an
optimized way (or they wouldn't have much added value apart from
transfering less bits on the wire; server processing load is IMO
equally important) and I don't know what browsers do when you use
these headers with a GWT RequestBuilder...

> On a related note, how is the usage of HEAD requests controlled? Do
> browsers use it at all? Can I give hints (either from client or server
> side) when to use HEAD to verify cache validity?

Why would you use HEAD to "verify cache validity"?
I don't think browsers use it at all by their own, but you should be
able to use it if you like (with RequestBuilder).


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