Simple REST service in Clojure

core.clj

(ns example.core
  (:require [org.httpkit.server :as http-kit]
            [compojure.api.sweet :refer :all]
            [ring.util.http-response :refer :all]))

(def counter (atom 0))                                      ;; declare counter

(defn greeting-handler [req]                                ;; ordinary clojure function, accepts request map, returns a response map
  (let [name (-> req :params :name (or "world"))]           ;; get param from url or use "world" by default
    (ok                                                     ;; wraps data with status code 200
      {:id   (swap! counter inc)                            ;; increment counter
       :name (str "Hello, " name "!")})))

(def app
  (api                                                      ;; wrap routes with useful middleware provided by compojure-api
    (GET "/greeting" [] greeting-handler)))

(defonce server                                             ;; declare server variable once
  (http-kit/run-server #'app {:port 8080}))                 ;; #'app allows to hot swap changes in handlers

Same service as in Spring docs example, but written in Clojure using Compojure API (routing and middleware) and http-kit server