A simple example to go with my post on Compojure. http://vedang.me/techlog/2012/02/23/composability-and-compojure/

routes.clj

(ns cello-world.routes
  (:require [compojure.route :as route]
            [compojure.core :as cc]
            [ring.util.response :as rur])
  (:use [ring.adapter.jetty :only [run-jetty]]))


(cc/defroutes hello-routes
  (cc/GET "/hello/name/" []
          (fn [req]
            (rur/response "<h1>Cello Vedang</h1>")))
  (cc/GET "/hello/city/" []
          (fn [req]
            (rur/response "<h1>Cello from Pune!</h1>"))))


(cc/defroutes main-routes*
  (cc/GET "/" [] (fn [req]
                   (rur/response "<h1>Cello World</h1>")))
  (cc/GET "/bye/" [] (fn [req]
                      (rur/response "<h1>Goodbye World</h1>")))
  (cc/GET "/hello*" [] hello-routes)
  (route/not-found "<h1>Page not found</h1>"))


(defn verify-secret
  "Verify that secret-key has been sent as a parameter s in the request"
  [handler]
  (fn [request]
    (if (= "s=please" (:query-string request))
      (handler request)
      {:status 403
       :body "You don't know the secret word"})))


;;; Wrap my main routes in swathes of middleware
(def main-routes (-> #'main-routes*
                     verify-secret))


(defonce ^:dynamic *server* nil)


(defn start-server
  [port]
  (let [server (run-jetty #'main-routes
                          {:port port
                           :join? false})]
    (println "Started server on port -" port)
    (alter-var-root #'*server* (constantly server))))


(defn stop-server
  []
  (.stop *server*))


(defn restart
  [port]
  (when (bound? #'*server*)
    (stop-server))
  (start-server port))


(comment
  ;; to run the program
  (start-server 5000)
  ;; The site should be accessible at 0.0.0.0:5002/
  ;; An example URL would be 0.0.0.0:5002/?s=please
  ;; to Stop the server
  (stop-server))