(defn- jar-stream-seq [stream]
  (take-while #(not= nil %) (repeatedly #(.getNextEntry stream))))

(defn- create-parent [archive-entry]
  (-> archive-entry (.getParentFile) (.mkdirs)))

(defn- extract-entry [entry dir jar-stream]
  (let [archive-entry (file dir (.getName entry))]
    (create-parent archive-entry)
    (cond (.isDirectory entry) (.mkdir archive-entry)
      :else (with-open [fos (FileOutputStream. archive-entry)]
              (copy jar-stream fos)))))

(defn unjar [src dest]
  (with-open [jar-stream (JarArchiveInputStream. (file-in-stream (file-str src)))]
    (let [dir (file dest)]
      (doseq [entry (jar-stream-seq jar-stream)] (extract-entry entry dir jar-stream)))))