Using Lisp or Scheme for runtime configuration of Java programs

Question

I have now seen several projects ending at a point where the actual configuration depended on things only available at run-time.

The typical way to configure a Java prog

Answer 1

I know you want a small size and runtime. Scheme is the usual choice for easy embedding, and would be my first choice. But I have no information on that field, though. My second choice is Clojure:

• Not that small; the jar is ~3 MB
• Overkill for a simple config reading, but the extra features can be safely ignored
• ~ Easy to call from Java: Calling clojure from java
• Full, excellent access to JVM
• Might invoke a small extra to the startup, which can be too much (see below)
• Now that I tried replicating the example's functionality with Clojure, I feel that Clojure isn't well suited for these kind of scripts (rc, etc). Clojure 1.3 will address some of that startup penalty but I don't know the magnitude of speed improvements coming

A respective code with using Clojure:

import clojure.lang.RT;
import clojure.lang.Var;
import clojure.lang.Compiler;
import java.io.FileReader;
import java.io.FileNotFoundException;

public class ClojTest {
    public static void main(String[] args) throws Exception {
        try {
            Compiler.load(new FileReader("hello.clj"));
        } catch(FileNotFoundException e) { return; }

        System.out.println("Message: '"+ RT.var("user", "msg").get() +"'");

        // Values
        int answer = (Integer) RT.var("user", "answer").get();

        // Function calls
        System.out.println(RT.var("user", "countdown").invoke(42));
    }
}

with hello.clj being:

(ns user)
(defn countdown [n]
  (reduce + (range 1 (inc n))))

(def msg "Hello from Clojure!")
(def answer (countdown 42))

Running time java ClojTest for a while yields in an average of 0.75 seconds. Clojure compiling the script has quite a penalty!