Clojure Ring เบื้องต้น

$ lein new hello-world
$ cd hello-world

(defproject hello-world "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "EPL-2.0 OR GPL-2.0-or-later WITH Classpath-exception-2.0"
            :url "https://www.eclipse.org/legal/epl-2.0/"}
  :dependencies [[org.clojure/clojure "1.10.0"]
                 [ring/ring-core "1.8.2"]
                 [ring/ring-jetty-adapter "1.8.2"]]
  :repl-options {:init-ns hello-world.core})

$ lein deps

(ns hello-world.core)

(defn handler [request]
  {:status 200
   :headers {"Content-Type" "text/html"}
   :body "Hello World"})

$ lein repl

=> (use 'ring.adapter.jetty)
=> (use 'hello-world.core)
=> (run-jetty handler {:port 3000
                       :join? false)

(defn what-is-my-ip [request]
  {:status 200
   :headers {"Content-Type" "text/plain"}
   :body (:remote-addr request)})

(defn wrap-content-type [handler content-type]
  (fn [request]
    (let [response (handler request)]
      (assoc-in response [:headers "Content-Type"] content-type))))

(def app
  (wrap-content-type handler "text/html"))

(def app
  (-> handler
      (wrap-content-type "text/html")
      (wrap-keyword-params)
      (wrap-params)))