On Tue, Apr 12, 2011 at 11:28 PM, Haris fbogdanovic@xnet.hr wrote:

Hi.

Can someone give me an example of using jsonp ? For example, I have a lisp function: (defun add (x y)    (+ x y)) and I want to call it from javascript: add (2, 2); How do I do that ?

It depends on the web-server. Here are some steps: 1. You need to define a query parameter that specifies the name of the callback javascript function. Popular choices are "callback" or "jsoncallback" 2. You need to set the response-type to application/javascript since it is not really json you return but a small javascript function call. 3. You need to get the x and y parameter, call add and generate a json-reponse. If the actual example is the add function the json equivalent to 4 is just 4 so you don't even need cl-json. 4. The json-reponse 4 should be made to look as a javascript function call, wrapped in parenthesis, end with a semicolon and have the callback function prepended. If you call mywebserver?fn=add&x=2&y=2&callback=foo you should generate this string as an answer: foo(4); And again served as application/javascript.

For hunchentoot, an untested implementation, not optimized for efficiency or safety:

(hunchentoot:define-easy-handler (jsonp-sample :uri "/add") (callback x y) (setf (hunchentoot:content-type*) "application/javascript") (let ((answer (+ x y))) (format nil "~a(~a);" callback (json:encode-json-to-string answer))))

I would start to test with an even easier version, with "alert" as a predefined callback and no x and y and no json-encode to see if you get hunchentoot running and get a response that works, then take it from there.

Hope it helps, /Henrik