Question

I’m trying to pull a value out of the url query string however I can return what I believe is a map, however when i use the below code, it doesn’t process it as expected. Can anyone advise how I access specific values in the returned querystring datastructure?

http://localhost:8080/remservice?foo=bar

(defroutes my-routes
  (GET "/" [] (layout (home-view)))
  (GET "/remservice*" {params :query-params} (str (:parameter params))))

Answer 1

You’ll need to wrap your handler in compojure.handler/api or compojure.handler/site to add appropriate middleware to gain access to :query-params. This used to happen automagically in defroutes, but no longer does. Once you do that, the {params :query-params} destructuring form will cause params to be bound to {"foo" "bar"} when you hit /remservice with foo=bar as the query string.

(Or you could add in wrap-params etc. by hand — these reside in various ring.middleware.* namespaces; see the code of compojure.handler (link to the relevant file in Compojure 1.0.1) for their names.)

E.g.

(defroutes my-routes
  (GET "/remservice*" {params :query-params}
       (str params)))

(def handler (-> my-routes compojure.handler/api))

; now pass #'handler to run-jetty (if that's what you're using)

If you now hit http://localhost:8080/remservice?foo=bar, you should see {"foo" "bar"} — the textual representation of your query string parsed into a Clojure map.