Rhino: read Javascript numbers returned from Java method

RhinoHowToReadJavascriptNumbersFromJavaMethod.java

package stackoverflow;

import sun.org.mozilla.javascript.internal.Context;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import java.util.Date;

/*
 * See question at http://stackoverflow.com/q/30185079/315306
 *
 * Program output:
 *
 *   Result: 1 (java.lang.Integer)
 *   Result: 9.0 (java.lang.Double)
 */
public class RhinoHowToReadJavascriptNumbersFromJavaMethod {

    public static void main(String... args) throws Exception {
        ScriptEngineManager mgr = new ScriptEngineManager();
        ScriptEngine engine = mgr.getEngineByName("JavaScript");
        try {
            Context ctx = Context.enter();
            ctx.getWrapFactory().setJavaPrimitiveWrap(false);
            engine.put("Conf", new Configuration());
            dumpResult(engine.eval("Conf.read('numbers.one')"));
            dumpResult(engine.eval("(Conf.read('numbers.one') + Conf.read('numbers.two')) * Conf.read('numbers.three')"));
        } finally {
            Context.exit();
        }
    }

    private static void dumpResult(Object res) {
        System.out.printf("Result: %s (%s)%n", res, res != null ? res.getClass().getName() : null);
    }

    public static class Configuration {

        public Object read(String key) {
            Object result;

            switch (key) {
                case "numbers.one":
                    result = 1;
                    break;
                case "numbers.two":
                    result = 2;
                    break;
                case "numbers.three":
                    result = 3;
                    break;
                case "strings.four":
                    result = "4";
                    break;
                case "dates.today":
                    result = new Date();
                    break;
                default:
                    result = null;
                    break;
            }

            return result;
        }
    }
}