Calling clojure script from java

Learned how to call clojure from java from Pablo's blog. Thank you, Pablo.

Add closure.jar to the java project( I have been using Eclipse). Use the following java code,

package pkg;

import clojure.lang.RT;
import clojure.lang.Var;

public class HelloWorld {
 private static String resPath = "pkg/clap.clj";
 public static void main(String[] args) {
  System.out.println("Java hello world");
  try {
   RT.loadResourceScript(resPath);
   Var mainVar = RT.var("pkg", "main");
   mainVar.invoke(args);
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
}

and the following clojure script in the same directory as the java source:

(ns pkg)
 
(defn main [args]
  (println "Hello World!")
  (println "Java main called clojure function with args: "
     (apply str (interpose " " args))))

Notes:
1. The java package name matches the clojure namespace.
2. (apply str (interpose " " args))
- interpose is a function; arguments are " " and args. From the online documentation: Returns a lazy seq of the elements of coll separated by sep
- apply is a function; applies function str (the 1st argument) to the argument list, which is the sequence returned by interpose.
3. So many functions. Here is the Clojure API online documentation
4. Control-Space on import clojure. and I see some important packages:
- clojure.lang.*
- clojure.core.*
- clojure.test.*
- clojure.inspector.*
- clojure.xml.*
- clojure.asm.*
- clojure.asm.commons.*

Of course, the whole idea is to develop in clojure - not java - and deploy into a JVM. So we probably won't be using the above packages very much (if at all!)

I need to find some interesting work - not too hard, but potentially useful to somebody.