myapp.middleware.clj

(ns myapp.middleware)

(defn wrap-content-type [handler content-type]
  (fn [req]
    (let [res (handler req)]
      (if-not (contains? (:headers req) "Content-Type")
        (assoc-in res [:headers "Content-Type"] content-type)
        res))))

myapp.server.clj

(ns myapp.server
  (:use [myapp.middleware :only (wrap-content-type)])
  (:require [noir.server :as server]))

(server/load-views "src/myapp/views/")

(defn -main [& m]
  (let [mode (keyword (or (first m) :dev))
        port (Integer. (get (System/getenv) "PORT" "8080"))]
    (server/add-middleware wrap-content-type "text/html")
    (server/start port {:mode mode
                        :ns 'myapp})))