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A Clojure library for à la carte (orthogonal) Ring request matching.

(Calf path is a synonym for Desire path. The Calf-Path is a poem by Sam Walter Foss.)

Why Calfpath?

  • Ring has no built-in routing mechanism; Calfpath delivers this essential feature.
  • Orthogonality - match URI patterns, HTTP methods or anything in a Ring request.
  • Calfpath is fast (benchmarks included) - there is no cost to what you do not use.
  • API is available as both dispatch macros and composable, data-driven routes.


Leiningen dependency: [calfpath "0.6.0"] (requires Clojure 1.7 or later)

Require namespace:

(require '[calfpath.core  :refer [->uri ->method ->get ->head ->options ->patch ->put ->post ->delete]])
(require '[calfpath.route :as r])

Direct HTTP URI/method dispatch

When you need to dispatch on URI pattern with convenient API:

(defn handler
  ;; ->uri is a macro that dispatches on URI pattern
  (->uri request
    "/user/:id*" [id]  (->uri request
                         "/profile/:type/" [type] (->method request
                                                    :get {:status 200
                                                          :headers {"Content-Type" "text/plain"}
                                                          :body (format "ID: %s, Type: %s" id type)}
                                                    :put {:status 200
                                                          :headers {"Content-Type" "text/plain"}
                                                          :body "Updated"})
                         "/permissions/"   []     (->method request
                                                    :get {:status 200
                                                          :headers {"Content-Type" "text/plain"}
                                                          :body (str "ID: " id)}
                                                    :put {:status 200
                                                          :headers {"Content-Type" "text/plain"}
                                                          :body (str "Updated ID: " id)}))
    "/company/:cid/dept/:did/" [cid did] (->put request
                                           {:status 200
                                            :headers {"Content-Type" "text/plain"}
                                            :body "Data"})
    "/this/is/a/static/route"  []        (->put request
                                           {:status 200
                                            :headers {"Content-Type" "text/plain"}
                                            :body "output"})))

Data-driven Routes abstraction

In many cases we need to manipulate (i.e. add and extend) the dispatch criteria before handling the requests. This can be addressed by the routes abstraction. Routes are a vector of route specification maps. Every route has three fundamental keys:

Key Required? Description
:matcher Yes (fn [request]) -> request? returns request on success and nil on failure
:nested Either Routes vector - nested match is attempted on this if matcher was successful
:handler Either (fn [request]) -> response returns Ring response map, like a Ring handler

Notes on routes

  • The :matcher key must be present in a route spec for dispatch.
    • In practice, other keys (e.g. :uri, :method etc.) add the :matcher key
  • Either :handler or :nested key must be present in a route spec.
  • A successful match may return an updated request, or the same request, or nil

See examples below:

;; a route-handler is arity-1 fn, like a ring-handler
(defn list-user-jobs
  [{:keys [user-id] :as request}]

(defn app-routes
  "Return a vector of route specs."
  [;; first route has a partial URI match,implied by a trailing '*'
   {:uri "/users/:user-id*" :nested [{:uri "/jobs/"        :nested [{:method :get  :handler list-user-jobs}
                                                                    {:method :post :handler assign-job}]}
                                     {:uri "/permissions/" :method :get :handler permissions-hanler}]}
   {:uri "/orders/:order-id/confirm/" :method :post :handler confirm-order}        ; :uri is lifted over :method
   {:uri "/health/"  :handler health-status}
   {:uri "/static/*" :handler (-> (fn [_] {:status 400 :body "No such file"})      ; static files serving example
                                ;; the following require Ring dependency in your project
                                (ring.middleware.resource/wrap-resource "public")  ; render files from classpath
                                (ring.middleware.file/wrap-file "/var/www/public") ; render files from filesystem

;; create a Ring handler from given routes
(def ring-handler
  (-> (app-routes)


You need JDK 1.7 or higher during development.

Running tests:

$ lein do clean, test
$ lein with-profile c17 test

Running performance benchmarks:

$ lein do clean, perf-test
$ lein with-profile c17,perf test  # on specified Clojure version


Copyright © 2015-2018 Shantanu Kumar (,

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.

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