Closing resources

gistfile1.clj

(ns example
  (:require [clojure.java.io :as io])
  (:import (java.io FileInputStream)
           (javax.mail Session)
           (javax.mail.internet MimeMessage)))

;; Good
(defn ^MimeMessage message
  [file]
  (with-open [fis (FileInputStream. (io/file file))]
    (MimeMessage. (Session/getDefaultInstance (System/getProperties)) fis)))

;; Bad
(defn ^MimeMessage message
  [file]
  (MimeMessage. (Session/getDefaultInstance (System/getProperties))
                (FileInputStream. (io/file file))))