How to load program resources in Clojure

Question

How do you load program resources such as icons, strings, graphical elements, scripts, and so on in a Clojure program? I am using a project layout similar to that in many Java p

Answer 1

I placed the file in testpkg/test.txt (relative to current directory).

Code:

(def x 5)
(def nm "testpkg/test.txt")
(def thr (Thread/currentThread))
(def ldr (.getContextClassLoader thr))
(def strem (.getResourceAsStream ldr nm))
(def strem2 (ClassLoader/getSystemResource nm))
(. System/out (println "First Approach:"))
(. System/out (println strem))
(. System/out (println))
(. System/out (println))
(. System/out (println "Second Approach:"))
(. System/out (println strem2))

$ java -cp .\;clojure.jar clojure.main test.clj

First Approach: java.io.BufferedInputStream@1549f94

Second Approach: file:/C:/jsight/javadevtools/clojure-1.1.0/testpkg/test.txt

Answer 2

It's the directory structure.

Continuing with the scripting engine example in the OP, a Clojure equivalent would be:

(ns com.domain.example
  (:gen-class)
  (:import (java.io InputStreamReader))
  (:import (javax.script ScriptEngineManager ScriptEngine)))

(defn load-resource
  [name]
  (let [rsc-name (str "com/domain/resources/" name)
        thr (Thread/currentThread)
        ldr (.getContextClassLoader thr)]
    (.getResourceAsStream ldr rsc-name)))

(defn markdown-to-html
  [mkdn]
  (let [manager (new ScriptEngineManager)
        engine (.getEngineByName manager "js")
        is (InputStreamReader. (load-resource "showdown.js"))
        _ (.eval engine is)
        cnv-arg (str "new Showdown.converter().makeHtml(\"" mkdn "\")")]
    (.eval engine cnv-arg)))

(defn -main
  []
  (println (markdown-to-html "plain, *emphasis*, **strong**")))

Note that the path to the resources is com/domain/resources for this code as opposed to com/domain/scriptingtest/resources in the Java version. In the clojure version, the source file, example.clj is in com/domain. In the Java version, the source file, Example.java is in the com/domain/scriptingtest package.

When setting up a project in my IDE, NetBeans, the Java project wizard asks for an enclosing package for the source. The Clojure plugin, enclojure, asks for a namespace, not a package. I had never noted that difference before. Hence the "off-by-one" error in the directory structure expected.

Answer 3

you can also use clojure.lang.RT/baseLoader

(defn serve-public-resource [path]
  (.getResourceAsStream (clojure.lang.RT/baseLoader) (str "public/" path))) 

Answer 4

(clojure.java.io/resource "myscript.js")