`lein new demo` で作って下のコードを貼り付けるだけ。

core.clj

(ns demo.core
  (:require [compojure.core :as c :refer [defroutes GET POST]]
            [hiccup.core :as h]
            [hiccup.form :as hf]
            [ring.adapter.jetty :as server]
            [ring.util.response :as res]))

(defn html-response [res]
  (res/content-type res "text/html;charset=utf-8"))

(defn test-handler [req]
  (-> [:div
       [:h1 "this is form page"]
       (hf/form-to
        [:post "/"]
        (hf/text-field :test))]
      h/html
      res/response
      html-response))

(defn post-test-handler [req]
  (-> (pr-str (slurp (:body req)))
      res/response
      html-response))

(defroutes app
  (GET "/" _ test-handler)
  (POST "/" _ post-test-handler))

(defonce server (atom nil))

(reset! server
        (server/run-jetty #'app {:port 3000 :join? false}))

project.clj

(defproject demo "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :dependencies [[org.clojure/clojure "1.8.0"]
                 [ring "1.4.0"]
                 [compojure "1.4.0"]
                 [hiccup "1.0.5"]])