Fetch & write a binary file using Clojure and clj-http

core.clj

(ns the-namespace.core
  (:require [clj-http.client :as client]
            [clojure.java.io :as io]))

(defn- fetch-photo!
  "makes an HTTP request and fetches the binary object"
  [url]
  (let [req (client/get url {:as :byte-array :throw-exceptions false})]
    (if (= (:status req) 200)
      (:body req))))

(defn- save-photo!
  "downloads and stores the photo on disk"
  [photo]
  (let [p (fetch-photo! (:url photo))]
    (if (not (nil? p))
      (with-open [w (io/output-stream (str "photos/" (:id photo) ".jpg"))]
        (.write w p)))))