[Lispweb] Body parsing

[Richard Newman]

Hello list,
   I'm new here, so hi! I've been hacking away with Araneida and Wilbur, 
doing assorted Semantic Web Lispy stuff. I have a 
question/suggestion/hack relating to Araneida that I'd like to throw up 
in the air.

   (Inline Lisp is surrounded by _underscores_ for clarity.)

   The Araneida _request_ class has a body for POST requests. 
_read-request-from-stream_ parses the HTTP body into an assoc list with 
the following line (line 27, daemon.lisp):

(parsed-body (if body (parse-body body '(#\&) len) nil))

   This is perfectly sane behaviour for x-www-form-urlencoded POST 
bodies (e.g. first=value&second=value). However, for all other bodies 
it is destructive and nonsensical (particularly XML, which uses =). 
Unfortunately, I'm working with those other bodies -- e.g. 
application/rdf+xml.

   My initial hack was to put in a simple test on the Content-Type 
header:

(parsed-body (if body
                 ;; Use member on the raw assoc list to make sure we 
catch requests
                 ;; with multiple Content-Types.
			  (if (member "application/x-www-form-urlencoded"
				      (cdr (assoc :content-type headers)) :test #'string=)
			    (parse-body body '(#\&) len)
			    body)
			  nil))

   i.e. only parse the body if we have form-encoded data; otherwise just 
use the body string (one could also url-unencode the body string). This 
split has the unfortunate side effect that for some requests 
_(request-body request)_ will return an assoc list, and sometimes a 
string. I don't know what consequences this would have on existing 
code. _(stringp)_ is one remedy; another would be to provide 
_body-data_ and _body-parsed_ (or similar names) slots on _request_, 
rather than just _body_. I would think that if Araneida-based 
applications are using the parsed data (and it's valid/correct) then 
their clients must be sending the correct headers (e.g. wget sends 
x-www-form-urlencoded by default), so putting this check in wouldn't 
break anything, but I might be wrong.

   Any thoughts, anyone?

   Regards,
-Richard
http://www.holygoat.co.uk/blog