core.clj

(ns demo.core
  (:use [ring.adapter.jetty :only (run-jetty)]
        [ring.middleware.session :only (wrap-session)]
        [ring.middleware.flash :only (wrap-flash)]
        [ring.middleware.stacktrace :only (wrap-stacktrace)]
        [hiccup.core :only (html)]
        [hiccup.form-helpers :only (form-to label text-field submit-button)]
        [hiccup.page-helpers :only (xhtml unordered-list)]
        [compojure.core :only (defroutes GET POST)]
        [compojure.route :only (not-found)]
        [ring.util.response :only (redirect)]))

(declare *flash*)

(defn wrap-flash-binding [handler]
  (fn [request]
    (binding [*flash* (request :flash)]
      (handler request))))

(defn message [title & message]
  (html [:h2 title]
        [:p message]))

(defn html-doc
  [title & body]
  (xhtml {:lang "en"}
    [:head [:title title]]
    [:body
      [:h1 title]
      (if *flash*
        (message "Flash" *flash*))
      body]))

(defn index-resource [errors count num]
  (html-doc "Demo"
    (if count
      (message "Count!"
        "The count is now " (or count 0))
    [:h2 "A form"]
    (form-to [:post "/"]
      (if-let [msg (errors key)]
        [:p "Error: " msg])
      (label :num num)
      (submit-button "Add"))))

(defn parse-int [n]
  (try (Integer/parseInt n)
       (catch NumberFormatException _ nil)))

(defn assoc-session [response session key value]
  (assoc-in response [:session key] value))

(defn flash [response & message]
  (assoc response :flash (apply str message)))

(defn invalid-number [key]
  {key "Please enter a number"})

(defn add-resource [{count :count :as session} num]
  (if-let [n (parse-int num)]
    (-> (redirect "/")
        (assoc-session :count (+ n (or count 0))
        (flash "Added " n " to " count)))
    (index-resource (invalid-number :num) count num)))

(defroutes main-routes
  (GET "/" {{{count :count} :session} {{num "num"} :params}}
    (index-resource {} count num)
  (POST "/" {{session :session} {{num "num"} :params}}
    (add-resource session num)
  not-found)

(def app
  (-> #'main-routes
      (wrap-flash-binding)
      (wrap-flash)
      (wrap-session)
      (wrap-stacktrace)))

(defn boot []
  (run-jetty #'app {:join? false :port 8080}))

project.clj

(defproject one-up "0.1.0-SNAPSHOT"
  :description      "Request Demo"
  :dependencies     [[org.clojure/clojure "1.2.0"]
                     [org.clojure/clojure-contrib "1.2.0"]
                     [ring/ring-core "0.3.3"]
                     [ring/ring-jetty-adapter "0.3.3"]
                     [compojure "0.5.2"]
                     [hiccup "0.3.0"]]
  :dev-dependencies [[ring/ring-devel "0.3.3"]
                     [swank-clojure "1.2.1"]])