Is there some way to let compojure support type conversion automatically?

Question

Now can use compojure this way:

(GET ["/uri"] [para1 para2]
   ）

Para1 and para2 are all of type String.

I would like to let it know the type correcttly,like this:

(GET ["/uri"] [^String para1 ^Integer para2]
   ）

It can convert para1 to be Sting and para2 to Integer.

Is there some library or good way to do this?

Answer 1

This is possible as of Compojure 1.4.0 using the syntax [x :<< as-int]

Answer 2

This is not currently possible with only Compojure.

You could use Prismatic schema coercion.

(require '[schema.core :as s])
(require '[schema.coerce :as c])
(require '[compojure.core :refer :all])
(require '[ring.middleware.params :as rparams])

(def data {:para1 s/Str :para2 s/Int s/Any s/Any})
(def data-coercer (c/coercer data c/string-coercion-matcher ))

(def get-uri
  (GET "/uri" r
        (let [{:keys [para1 para2]}  (data-coercer (:params r))]
                 (pr-str {:k1 para1 :k2 (inc para2)}))))

(def get-uri-wrapped
  (let [keywordizer (fn [h]
                      (fn [r]
                        (h (update-in r [:params] #(clojure.walk/keywordize-keys %)))))]
    (-> get-uri keywordizer rparams/wrap-params)))

Here is a sample run:

(get-uri-wrapped {:uri "/uri" :query-string "para1=a&para2=3" :request-method :get})

{:status 200,
 :headers {"Content-Type" "text/html; charset=utf-8"},
 :body "{:k1 \"a\", :k2 4}"}