web.clj

(ns joy.web
  (:import (com.sun.net.httpserver HttpHandler HttpExchange HttpServer)
	   (java.net InetSocketAddress HttpURLConnection)
	   (java.io IOException FilterOutputStream)
	   (java.util Arrays)))

(defn default-handler [txt]
  (proxy [HttpHandler] []
    (handle [exchange]
	    (.sendResponseHeaders exchange HttpURLConnection/HTTP_OK (.length txt))
	    (doto (.getResponseBody exchange)
	      (.write (.getBytes txt))
	      (.close)))))

(defn new-server [port path handler]
  (doto (HttpServer/create (InetSocketAddress. port) 0)
    (.createContext path handler)
    (.setExecutor nil)
    (.start)))


(defn change-message
  "Convenience method to change a proxy's output message"
  ([p txt] (change-message p identity txt))
  ([p fltr txt]
     (update-proxy p
		   {"handle"
		    (fn [this exchange]
		      (let [txt (fltr txt)
			    b (.getBytes txt)]
			(.sendResponseHeaders exchange
					      HttpURLConnection/HTTP_OK
					      (count b))
			(doto (.getResponseBody exchange)
			  (.write b)
			  (.close))))})))

(defn aloha-filter [#^String s]
  (.replaceAll s "Hello" "Aloha"))

Thanks again for this. It gave me some good ideas for the refactoring.
:f