JSObject.call(), closures, JS anonymous function references etc

"Richard Maher" <maher_rj@hotspamnotmail.com>
Sat, 14 Mar 2009 10:02:09 +0800

Using netscape.javascript.JSObject (LiveConnect) I want/need to pass a
Function Reference to my Java Applet so that it can either call that
directly, or pass it to a static JavaScript function that will then redirect
the call to the appropriate anonymous function that formed a closure.

Please forgive me if the terminology is not strictly correct, but I hope you
can still understand what I'm trying to do.

I thought the second argument to JSObject.call could be an array of Strings
*or* Objects but trying to get a JavaScript object (or a reference/pointer
to it) to survive the Java Applet membrane (without some sort of
serialize/deserialize) is proving difficult. Am I missing something obvious?
Does anyone have a small example I can look at?

Maybe it's as easy as the first argument to JSObject.call can be a
JavaScript VARiable? I'll give it a go. . .

Cheers Richard Maher

//This is called from the "onload" event
    function load() {
      myFunc = setClosure();
      chan = document.getElementById("AnonCallApplet");
// This is called from the Applet
    function jsMethod(javaInt, javaFunc) {
      alert('Integer ' + javaInt);
      alert('JavaFunc ' + javaFunc.toString());

    function setClosure() {
      var lclNum = 0;
      return function(){
                alert("lclNum = " + lclNum);
// This is called by some user-driven event (onchange, onclick. . ).
    function callApplet() {
      chan.javaMethod(step, myFunc)
      return true;

//Here's the Applet

import java.applet.Applet;
import java.io.IOException;
import netscape.javascript.JSObject;
import netscape.javascript.JSException;

public class AnonCallApplet extends Applet {

    private JSObject browser;
    private static int sumNum = 0;
    private int addNum;

    public void init(){
        try {
            browser = JSObject.getWindow(this); }
        catch (netscape.javascript.JSException e) {
            e.printStackTrace(); }
        catch (Exception e) {
            e.printStackTrace(); }

    public void javaMethod (String jsNum, String jsFunc) {

        addNum = Integer.parseInt(jsNum);

        sumNum += addNum;
        Object args[] = {(Object)new Integer(sumNum), (Object)jsFunc};
        try {
            browser.call("jsMethod", args);}
        catch (JSException e){
            System.out.println("Error when calling jsMethod()"); }

    public void destroy() {

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