There was no way to do this, but I just added the 92nd keyword to
serve/servlet to do it:
#:servlet-responder
(λ (url exn)
(response/xexpr
`(html (body "Some other message"))))
allows you to inspect the exception and return a different thing.
(The push will happen shortly.)
Jay
On Mon, Apr 23, 2012 at 3:35 PM, Galler <lzgal...@optonline.net> wrote:
> Description:
>
> the stateless webserver allows a user to generate a stuffer to manipulate
> the encoding of the ANF sent to the client in the URL
>
> For example
>
> (stuffer-chain serialize-stuffer (stuffer-compose base64-stuffer
> (HMAC-SHA1-stuffer #"mysupersecretkey")))
>
> will prepend a digest to the base64-encoded ANF, and recompute and
> authenticate the digest on receipt.
>
> If either the encoded ANF, or the digest has been altered (i.e. forged) by
> the client, the stuffer correctly throws an error, which is caught by the
> webserver, which sends the following response back to the client:
>
> <some html>
> Exception
>
> The application raised an exception with the message:
>
> HMAC-SHA1-stuffer: Signature does not match!
>
> </some html>
>
> Question:
>
> While the behavior is absolutely correct, is there someplace to set a
> response if an error occurs with the stuffer? Is the error caught at the
> top-level of the dispatching server and not available for customization?
>
> If the answer is the latter, its ***not*** critical and probably not
> important to implement.
>
> Example code: Once running, alter the url in your browser in any manner
> (character addition, deletion, substitution) to generate the expected error.
>
> #lang web-server
>
>
> (require web-server/stuffers)
> (provide/contract (start (request? . -> . response?)))
>
> (define (start request)
> (phase-1 request))
>
> ; phase-1: request -> response
> (define (phase-1 request)
> (local [(define (response-generator embed/url)
> (response/xexpr
> `(html
> (body (h1 "Phase 1")
> (a ((href ,(embed/url phase-2)))
> "click me!")))))]
> (send/suspend/dispatch response-generator)))
>
> ; phase-2: request -> response
> (define (phase-2 request)
> (display (request-bindings/raw request))
> (local [(define (response-generator embed/url)
> (response/xexpr
> `(html
> (body (h1 "Phase 2")
> (a ((href ,(embed/url phase-1)))
> "click me!")))))]
> (send/suspend/dispatch response-generator)))
>
>
> (require web-server/servlet-env)
> (serve/servlet start
> #:stateless? #t
> #:launch-browser? #t
> #:connection-close? #t
> #:stuffer (stuffer-chain serialize-stuffer (stuffer-compose
> base64-stuffer (HMAC-SHA1-stuffer #"mysupersecretkey")))
> #:quit? #f
> #:listen-ip #f
> #:servlet-path "/")
> ____________________
> Racket Users list:
> http://lists.racket-lang.org/users
--
Jay McCarthy <j...@cs.byu.edu>
Assistant Professor / Brigham Young University
http://faculty.cs.byu.edu/~jay
"The glory of God is Intelligence" - D&C 93
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