Thursday Sep 26, 2013

setInterval and setTimeout JavaScript Functions

With people porting HTML to Nashorn + JavaFX more frequently, I often get asked the question "how do you port functions like setInterval and setTimeout" (setInterval is used to have a function repeated at regular intervals, where setTimeout is used to have a function delayed.) The following code duplicates the functionality of the each of the setInterval family of functions, when used in a JavaFX application.

var Platform = Java.type("javafx.application.Platform");
var Timer    = Java.type("java.util.Timer");

function setInterval(func, milliseconds) {
	// New timer, run as daemon so the application can quit
	var timer = new Timer("setInterval", true);
	timer.schedule(function() Platform.runLater(func), milliseconds, milliseconds);	
	return timer;

function clearInterval(timer) {

function setTimeout(func, milliseconds) {
	// New timer, run as daemon so the application can quit
	var timer = new Timer("setTimeout", true);
	timer.schedule(function() Platform.runLater(func), milliseconds);	
	return timer;

function clearTimeout(timer) {

<Update March 21, 2014>

I was requested by a reader to implement setInterval, setTimeout and setImmediate with the same arguments as defined in DOM.

var Platform = Java.type("javafx.application.Platform");
var Timer    = Java.type("java.util.Timer");

function setTimerRequest(handler, delay, interval, args) {
    handler = handler || function() {};
    delay = delay || 0;
    interval = interval || 0;

    var applyHandler = function() handler.apply(this, args);
    var runLater = function() Platform.runLater(applyHandler);

    var timer = new Timer("setTimerRequest", true);

    if (interval > 0) {
        timer.schedule(runLater, delay, interval);
    } else {
        timer.schedule(runLater, delay);

    return timer;

function clearTimerRequest(timer) {

function setInterval() {
    var args =;
    var handler = args.shift();
    var ms = args.shift();

    return setTimerRequest(handler, ms, ms, args);

function clearInterval(timer) {

function setTimeout() {
    var args =;
    var handler = args.shift();
    var ms = args.shift();

    return setTimerRequest(handler, ms, 0, args);

function clearTimeout(timer) {

function setImmediate() {
    var args =;
    var handler = args.shift();

    return setTimerRequest(handler, 0, 0, args);

function clearImmediate(timer) {

Monday Sep 09, 2013

Nashorn + FX 350fps vs. Chrome 120fps

I was reading an article written by Felix Bembrick where he took a Chrome canvas example and ported it to Nashorn with JavaFX.  I ran the two tests myself and was surprised to see that Nashorn + FX ran at 350fps where Chrome ran at 120fps (iMac, 3.4 GHz Intel Core i7, AMD Radeon HD 6970M 2048M.)  Much of the credit for that is JavaFX's rendering engine, but Nashorn allowed Felix to leverage that.  The original article is at JavaFX with Nashorn Canvas example

Wednesday Sep 04, 2013

JavaOne: What a Difference a Year Makes

I haven't been blogging for a while.  JavaOne examples and slides are taking up all my time.  Marcus and Attila leaked out that I was doing a demo of the Nashorn Debugger prototype, but I still have some surprises up my sleeve.  I was reviewing examples from last year and felt that they needed some updating.  The FX Fireworks example had all kinds of Java code to support applications, timers and callbacks.  This year's Fireworks version is pure Nashorn.  I posted source and backdrop here.  Just run with jjs -fx -scripting fireworks.js  Enjoy.

var ArrayList      = Java.type("java.util.ArrayList");
var File           = Java.type("");

var AnimationTimer = Java.type("javafx.animation.AnimationTimer");
var BlendMode      = Java.type("javafx.scene.effect.BlendMode");
var Canvas         = Java.type("javafx.scene.canvas.Canvas");
var Color          = Java.type("javafx.scene.paint.Color");
var CycleMethod    = Java.type("javafx.scene.paint.CycleMethod");
var Group          = Java.type("javafx.scene.Group");
var ImageView      = Java.type("javafx.scene.image.ImageView");
var Pane           = Java.type("javafx.scene.layout.Pane");
var RadialGradient = Java.type("javafx.scene.paint.RadialGradient");
var Reflection     = Java.type("javafx.scene.effect.Reflection");
var Scene          = Java.type("javafx.scene.Scene");
var Stop           = Java.type("javafx.scene.paint.Stop");

var AnimationTimerExtend = Java.extend(AnimationTimer);

var doubleArray    = Java.type("double[]");

var GRAVITY = 0.06;

function Particle(posX, posY, velX, velY, targetX, targetY, color, size, usePhysics, shouldExplodeChildren, hasTail) {
    this.posX                  = posX;
    this.posY                  = posY;
    this.velX                  = velX;
    this.velY                  = velY;
    this.targetX               = targetX;
    this.targetY               = targetY;
    this.color                 = color;
    this.size                  = size;
    this.usePhysics            = usePhysics;
    this.shouldExplodeChildren = shouldExplodeChildren;
    this.hasTail               = hasTail;
    this.alpha                 = 1;
    this.easing                = Math.random() * 0.02;
    this.fade                  = Math.random() * 0.1;

Particle.prototype.update = function() {
    this.lastPosX = this.posX;
    this.lastPosY = this.posY;

    if(this.usePhysics) { // on way down
        this.velY += GRAVITY;
        this.posY += this.velY;
        this.alpha -= this.fade; // fade out particle
    } else { // on way up
        var distance = (this.targetY - this.posY);
        // ease the position
        this.posY += distance * (0.03 + this.easing);
        // cap to 1
        this.alpha = Math.min(distance * distance * 0.00005, 1);

    this.posX += this.velX;

    return this.alpha < 0.005;

Particle.prototype.draw = function(context) {
    var x    = Math.round(this.posX);
    var y    = Math.round(this.posY);
    var xVel = (x - this.lastPosX) * -5;
    var yVel = (y - this.lastPosY) * -5;

    // set the opacity for all drawing of this particle
    context.globalAlpha = Math.random() * this.alpha;
    // draw particle
    context.fill = this.color;
    context.fillOval(x - this.size, y - this.size, this.size + this.size, this.size + this.size);

    // draw the arrow triangle from where we were to where we are now
    if (this.hasTail) {
        context.fill = Color.rgb(255, 255, 255, 0.3);
        var x = new doubleArray(3);
        var y = new doubleArray(3);
        x[0] = this.posX + 1.5;  y[0] = this.posY;
        x[1] = this.posX + xVel; y[1] = this.posY + yVel;
        x[2] = this.posX - 1.5;  y[2] = this.posY;
        context.fillPolygon(x, y, 3);

function drawFireworks(gc) {
    var iter = particles.iterator();
    var newParticles = new ArrayList();

    while(iter.hasNext()) {
        var firework =;

        // if the update returns true then particle has expired
        if(firework.update()) {
            // remove particle from those drawn

            // check if it should be exploded
            if(firework.shouldExplodeChildren) {
                if(firework.size == 9) {
                    explodeCircle(firework, newParticles);
                } else if(firework.size == 8) {
                    explodeSmallCircle(firework, newParticles);



function fireParticle() {
    particles.add(new Particle(
        surface.width * 0.5, surface.height + 10,
        Math.random() * 5 - 2.5, 0,
        0, 150 + Math.random() * 100,
        colors[0], 9,
        false, true, true));

function explodeCircle(firework, newParticles) {
    var count = 20 + (60 * Math.random());
    var shouldExplodeChildren = Math.random() > 0.5;
    var angle = (Math.PI * 2) / count;
    var color = (Math.random() * (colors.length - 1));

    for(var i=count; i>0; i--) {
        var randomVelocity = 4 + Math.random() * 4;
        var particleAngle = i * angle;

            new Particle(
                firework.posX, firework.posY,
                Math.cos(particleAngle) * randomVelocity, Math.sin(particleAngle) * randomVelocity,
                0, 0,
                true, shouldExplodeChildren, true));

function explodeSmallCircle(firework, newParticles) {
    var angle = (Math.PI * 2) / 12;

    for(var count = 12; count > 0; count--) {
        var randomVelocity = 2 + Math.random() * 2;
        var particleAngle = count * angle;
            new Particle(
                firework.posX, firework.posY,
                Math.cos(particleAngle) * randomVelocity, Math.sin(particleAngle) * randomVelocity,
                0, 0,
                true, false, false));

function fileToURL(file) {
    return new File(file).toURI().toURL().toExternalForm();

var timer = new AnimationTimerExtend() {
    handle: function handle(now) {
        var gc = surface.graphicsContext2D;
        // clear area with transparent black
        gc.fill = Color.rgb(0, 0, 0, 0.2);
        gc.fillRect(0, 0, 1024, 708);
        // draw fireworks

        // countdown to launching the next firework
        if (countDownTillNextFirework <= 0) {
            countDownTillNextFirework = 10 + (Math.random() * 30);


// Kill timer before exiting.
function stop() {

var particles = new ArrayList();
var countDownTillNextFirework = 40;

// create a color palette of 180 colors
var colors = new Array(181);
var stops = new ArrayList();
stops.add(new Stop(0, Color.WHITE));
stops.add(new Stop(0.2, Color.hsb(59, 0.38, 1)));
stops.add(new Stop(0.6, Color.hsb(59, 0.38, 1,0.1)));
stops.add(new Stop(1, Color.hsb(59, 0.38, 1,0)));
colors[0] = new RadialGradient(0, 0, 0.5, 0.5, 0.5, true, CycleMethod.NO_CYCLE, stops);

for (var h = 0; h < 360; h += 2) {
    var stops2 = new ArrayList();
    stops2.add(new Stop(0, Color.WHITE));
    stops2.add(new Stop(0.2, Color.hsb(h, 1, 1)));
    stops2.add(new Stop(0.6, Color.hsb(h, 1, 1,0.1)));
    stops2.add(new Stop(1, Color.hsb(h, 1, 1,0)));
    colors[1 + (h / 2)] = new RadialGradient(0, 0, 0.5, 0.5, 0.5, true, CycleMethod.NO_CYCLE, stops2);

var surface = new Canvas(1024, 500);
surface.blendMode = BlendMode.ADD;
surface.effect = new Reflection(0, 0.4, 0.15, 0);

var imageUrl = fileToURL("sf.jpg");
var background = new ImageView(imageUrl);

var pane = new Pane();

var root = new Group();
$STAGE.scene = new Scene(root);


Wednesday May 29, 2013

Repost: Taming the Nashorn (first impressions)...

[This is a repost of an article written by our friend @hansolo_ with his permission.  The original article is at  Taming the Nashorn (first impressions)...]

Hi there,

JavaScript is everywhere these days and so it is also part of JDK8 dev. prev. with Project Nashorn which is a lightweight high-performance JavaScript runtime engine.

Because I never used Rhino (which is in principle the same just older and slower) I had no  idea how to use it and for what reason.

After I met Marcus Lagergren (@lagergren) at JAX in Mainz (Germany), Geecon in Krakow (Poland) and at Java Forum in Malmö (Sweden) I decided that I have to take a look at the Nashorn to get an idea on how to use it. Of course I'm especially interested on how to use Nashorn in combination with JavaFX. Lucky me that Nashorn is part of the weekly developer previews of JDK8 since a few weeks ago and because Jim Laskey (@wickund) blogged about this use case I was able to start with it yesterday.

After some starting problems I slowly begin to understand and would like to share it with you...

First of all I would like to see how I could use Nashorn with JavaScript in combination with my controls, so the idea is to visualize a Lcd control of my Enzo library with Nashorn.

For the following example you'll need the jdk8 developer preview (grab it here) and a current version of my Enzo library (grab it here).

And with a shell and a text editor you are good to go...really nice :)

So first of all we need to create a JavaScript file that should create a JavaFX application which should show the Lcd control and set's the value of the Lcd control every 3 seconds to a random value between 0 and 100.

This is the JavaFX code to realize that...

import eu.hansolo.enzo.lcd.Lcd;
import eu.hansolo.enzo.lcd.LcdBuilder;
import javafx.animation.AnimationTimer;
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import java.util.Random;
public class EnzoFX extends Application {
  private Lcd            lcd;
  private Random         random;
  private long           lastTimerCall;
  private double         charge;
  private AnimationTimer timer;
  @Override public void init() {
    // Initialize the AnimationTimer
    random        = new Random();
    lastTimerCall = System.nanoTime();
    charge        = 0;
    timer         = new AnimationTimer() {
      @Override public void handle(long now) {
        if (now > lastTimerCall + 3_000_000_000l) {
          lcd.setValue(random.nextDouble() * 100);
          charge += 0.02;
          if (charge > 1.0) charge = 0.0;
          lastTimerCall = now;
    // Initialize the Enzo Lcd control
    lcd = LcdBuilder.create()
                    .title("Room Temp")
  @Override public void start(Stage stage) {
    // Prepare stage and add controls
    StackPane root = new StackPane();
    root.setPadding(new Insets(10, 10, 10, 10));
    stage.setTitle("Enzo in JavaFX");
    stage.setScene(new Scene(root, 528, 192));;
    // Start the timer
  public static void main(String[] args) {

Ok, so now we know how to achieve this in JavaFX but now let's take a look at the JavaScript code that leads to the same result. Here you go...

var System         = java.lang.System;
var Random         = java.util.Random;
var StackPane      = javafx.scene.layout.StackPane;
var Scene          = javafx.scene.Scene;
var Insets         = javafx.geometry.Insets;
var AnimationTimer = javafx.animation.AnimationTimer;
var Lcd            =;
// Initialize the AnimationTimer
var random        = new Random();
var lastTimerCall = System.nanoTime();
var charge        = 0;
var timer         = new AnimationTimer() {
    handle: function(now) {
        if (now > lastTimerCall + 3000000000) {
            lcd.value = random.nextDouble() * 100;
            lcd.trend = Lcd.Trend.values()[random.nextInt(5)];
            charge += 0.02;
            if (charge > 1.0) charge = 0.0;
            lcd.batteryCharge = charge;
            lastTimerCall = now;
// Initialize the Enzo Lcd control
var lcd   = new Lcd();
lcd.title                    = "Room Temp";
lcd.unit                     = "°C";
lcd.decimals                 = 2;
lcd.minMeasuredValueDecimals = 2;
lcd.maxMeasuredValueDecimals = 2;
lcd.unitVisible              = true;
lcd.batteryVisible           = true;
lcd.alarmVisible             = true;
lcd.minMeasuredValueVisible  = true;
lcd.maxMeasuredValueVisible  = true;
lcd.lowerRightTextVisible    = true;
lcd.formerValueVisible       = true;
lcd.trendVisible             = true;
lcd.lowerRightText           = "Info";
lcd.valueAnimationEnabled    = true;
lcd.foregroundShadowVisible  = true;
lcd.crystalOverlayVisible    = true;
// Prepare the stage and add controls
var root     = new StackPane();
root.padding = new Insets(10, 10, 10, 10);
$STAGE.title = "Enzo with Nashorn";
$STAGE.scene = new Scene(root, 528, 192);
// Start the timer

The JavaScript code that I saved to a file "javafx.js" looks not that different from the JavaFX code's JavaScript...and the resulting application will look like this...

You might ask yourself how you could run this code and here is the answer, all it takes is one call on the command line that looks like this:

-cp /PATH/TO/LIBRARY/Enzo.jar -fx /PATH/TO/JS-FILE/javafx.js

Means you have to now the path to your jdk8 installation folder where you could find the jjs executable that is needed to start nashorn from the command line. In addition you have to add the Enzo.jar to the classpath so that you could use it within your JavaScript file and at last you have to call the JavaScript file with the -fx parameter which will start the application....BAM...that's all...sweet :)

I've put the commandline in a bash script so that I could call it by simple calling the bash script instead of typing the whole line over and over again.

If you start the javafx.js file you should see something like on this youtube video.

Ok you might say where is the advantage of using JavaScript to run a JavaFX application...just think about not starting an IDE, not compiling and building a JavaFX application just to make a short test. Isn't it be much nicer to simply have a small JavaScript, edit it with your default text editor and run it with from the command line with one single call...I really like that for testing things.

If you would like to know more about Nashorn you should definitely take a look at the Nashorn blog ,subscribe to the Nashorn mailing list and take a look at the Nashorn Wiki.

At this point I would say THANK YOU to Jim Laskey and Marcus Lagergren which helped me to getting this stuff done!!!

This is really a first test of using Nashorn with JavaFX but now that I know how to use it I will use more stay tuned and keep coding...

Tuesday May 07, 2013

jjs -fx

So after some playing around and working with the JavaFX folks, I think we have a proposal for jjs that works with JavaFX.  The -fx flag on jjs will bootstrap scripts using a javafx.application.Application.  Thus, writing JavaFX scripts in Nashorn is very easy.

The basic command line is;
	jjs -fx fxscript.js
You can mix and match other jjs options like -scripting and -- ;
	jjs -fx -scripting fxscript.js -- my script args
The content of the script follows some of the examples I've posted before.  The script may optionally contain JavaFX init, start and/or stop functions.  What is new, is that you can leave them behind and just straight script.  The original hello world example;

var Button    = Java.type("javafx.scene.control.Button");
var StackPane = Java.type("javafx.scene.layout.StackPane");
var Scene     = Java.type("javafx.scene.Scene");

function start(stage) {
    stage.title = "Hello World!";
    var button = new Button();
    button.text = "Say 'Hello World'";
    button.onAction = function() print("Hello World!");
    var root = new StackPane();
    stage.scene = new Scene(root, 300, 250);;


var Button    = Java.type("javafx.scene.control.Button");
var StackPane = Java.type("javafx.scene.layout.StackPane");
var Scene     = Java.type("javafx.scene.Scene");

$STAGE.title = "Hello World!";
var button = new Button();
button.text = "Say 'Hello World'";
button.onAction = function() print("Hello World!");
var root = new StackPane();
$STAGE.scene = new Scene(root, 300, 250);

where the stage is now a global var $STAGE (instead of the start function argument.)

Also for convenience, we've predefined includes for all of the JavaFX classes.  I would recommend using only the classes you need (only needed for new and for static field access), but for prototyping having includes really helps things move along.

The hello world example can then be rewritten as;


$STAGE.title = "Hello World!";
var button = new Button();
button.text = "Say 'Hello World'";
button.onAction = function() print("Hello World!");
var root = new StackPane();
$STAGE.scene = new Scene(root, 300, 250);

The complete set of includes are as follows;









Here are a couple more examples;

// fx3d.js

var material = new PhongMaterial();
material.diffuseColor = Color.LIGHTGREEN;
material.specularColor = Color.rgb(30, 30, 30);

var meshView =[
    new Box(200, 200, 200),
    new Sphere(100),
    new Cylinder(100, 200)
], "javafx.scene.shape.Shape3D[]");

for (var i = 0; i != 3; i++) {
    meshView[i].material = material;
    meshView[i].translateX = (i + 1) * 220;
    meshView[i].translateY = 500;
    meshView[i].translateZ = 20;
    meshView[i].drawMode = DrawMode.FILL;
    meshView[i].cullFace = CullFace.BACK;

var pointLight = new PointLight(Color.WHITE);
pointLight.translateX = 800;
pointLight.translateY = -200;
pointLight.translateZ = -1000;

var root = new Group(meshView);

var scene = new Scene(root, 800, 800, true);
scene.fill = Color.rgb(127, 127, 127); = new PerspectiveCamera(false);
$STAGE.scene = scene;

// ColorfulCircles.js


var WIDTH = 500;
var HEIGHT = 600;
var animation;

function setup(primaryStage) {
    var root = new Group();
    primaryStage.resizable = false;
    var scene = new Scene(root, WIDTH, HEIGHT);
    scene.title = "Colourful Circles";
    primaryStage.scene = scene;
    // create first list of circles
    var layer1 = new Group();
    for(var i = 0; i < 15; i++) {
        var circle = new Circle(200, Color.web("white", 0.05));
        circle.strokeType = StrokeType.OUTSIDE;
        circle.stroke = Color.web("white", 0.2);
        circle.strokeWidth = 4;
    // create second list of circles
    var layer2 = new Group();
    for(var i = 0; i < 20; i++) {
        var circle = new Circle(70, Color.web("white", 0.05));
        circle.strokeType = StrokeType.OUTSIDE;
        circle.stroke = Color.web("white", 0.1);
        circle.strokeWidth = 2;
    // create third list of circles
    var layer3 = new Group();
    for(var i = 0; i < 10; i++) {
        var circle = new Circle(150, Color.web("white", 0.05));
        circle.strokeType = StrokeType.OUTSIDE;
        circle.stroke = Color.web("white", 0.16);
        circle.strokeWidth = 4;
    // Set a blur effect on each layer
    layer1.effect = new BoxBlur(30, 30, 3);
    layer2.effect = new BoxBlur(2, 2, 2);
    layer3.effect = new BoxBlur(10, 10, 3);
    // create a rectangle size of window with colored gradient
    var colors = new Rectangle(WIDTH, HEIGHT,
            new LinearGradient(0, 1, 1, 0, true, CycleMethod.NO_CYCLE,
                               new Stop(0,    Color.web("#f8bd55")),
                               new Stop(0.14, Color.web("#c0fe56")),
                               new Stop(0.28, Color.web("#5dfbc1")),
                               new Stop(0.43, Color.web("#64c2f8")),
                               new Stop(0.57, Color.web("#be4af7")),
                               new Stop(0.71, Color.web("#ed5fc2")),
                               new Stop(0.85, Color.web("#ef504c")),
                               new Stop(1,    Color.web("#f2660f"))));
    colors.blendMode = BlendMode.OVERLAY;
    // create main content
    var group = new Group(new Rectangle(WIDTH, HEIGHT, Color.BLACK),
    var clip = new Rectangle(WIDTH, HEIGHT);
    clip.smooth = false;
    group.clip = clip;
    // create list of all circles
    var allCircles = new java.util.ArrayList();
    // Create a animation to randomly move every circle in allCircles
    animation = new Timeline();
    for each (var circle in allCircles) {
              new KeyFrame(Duration.ZERO, // set start position at 0s
                           new KeyValue(circle.translateXProperty(), Math.random() * WIDTH),
                           new KeyValue(circle.translateYProperty(), Math.random() * HEIGHT)),
              new KeyFrame(new Duration(20000), // set end position at 20s
                           new KeyValue(circle.translateXProperty(), Math.random() * WIDTH),
                           new KeyValue(circle.translateYProperty(), Math.random() * HEIGHT))
    animation.autoReverse = true;
    animation.cycleCount = Animation.INDEFINITE;

function stop() {

function play() {;

function start(primaryStage) {

Saturday Apr 06, 2013

To Shell Or Not To Shell

I find myself facing a dilemma today. How should I use Java FX from Nashorn? So far, I have two approaches I could use, but each comes with some issues. Some background first.

Java FX, even though ships with the JDK, is on a different build cycle and has dependencies on elements of the JDK. This arraignment limits Nashorn, which is part of the JDK, from actually having dependencies into Java FX. But, there is a dependency requirement to implement a Java FX application. Java FX applications begin with a subclass instance of javafx.application.Application. Therefore, whatever choice is made, it has to be independent of the JDK (at some point should be part of Java FX.)

The first approach, in general terms, is the easiest to use. It involves using a predefined shell that is similar to jjs but handles the overrides of Application methods init, start and finish. The source of this shell is currently checked into the Nashorn repo under nashorn/tools/fxshell.

 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit if you need additional information or have any
 * questions.
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.stage.Stage;
import javax.script.Invocable;
import javax.script.ScriptContext;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineFactory;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import jdk.nashorn.api.scripting.NashornScriptEngineFactory;
 * This shell is designed to launch a JavaFX application written in Nashorn JavaScript.
public class FXShell extends Application {
     * Script engine manager to search.
    private ScriptEngineManager manager;
     * Nashorn script engine factory.
    private NashornScriptEngineFactory factory;
     * Main instance of Nashorn script engine.
    private ScriptEngine engine;
     * Needed so that the FX launcher can create an instance of this class.
    public FXShell() {
     * Main entry point. Never actually used.
     * @param args Command line arguments.
    public static void main(String[] args) {
     * Application overrides.
    public void init() throws Exception {
        // Script engine manager to search.
        this.manager = new ScriptEngineManager();
        // Locate the Nashorn script engine factory.  Needed for passing arguments.
        for (ScriptEngineFactory engineFactory : this.manager.getEngineFactories()) {
             if (engineFactory.getEngineName().equals("Oracle Nashorn") &&
                 engineFactory instanceof NashornScriptEngineFactory) {
                this.factory = (NashornScriptEngineFactory)engineFactory;
        // If none located.
        if (this.factory == null) {
            System.err.println("Nashorn script engine not available");
        // Get the command line and JNLP parameters.
        final Parameters parameters = getParameters();
        // To collect the script paths and command line arguments.
        final List<String> paths = new ArrayList<>();
        final List<String> args = new ArrayList<>();
        // Pull out relevant JNLP named parameters.
        final Map<String, String> named = parameters.getNamed();
        for (Map.Entry<String, String> entry : named.entrySet()) {
            final String key = entry.getKey();
            final String value = entry.getValue();
            if ((key.equals("cp") || key.equals("classpath")) && value != null) {
            } else if (key.equals("source") && value != null &&
                       value.toLowerCase().endsWith(".js")) {
        // Pull out relevant command line arguments.
        boolean addNextArg = false;
        boolean addAllArgs = false;
        for (String parameter : parameters.getUnnamed()) {
            if (addAllArgs || addNextArg) {
                addNextArg = false;
            } else if (parameter.equals("--")) {
                addAllArgs = true;
            } else if (parameter.startsWith("-")) {
                addNextArg = parameter.equals("-cp") || parameter.equals("-classpath");
            } else if (parameter.toLowerCase().endsWith(".js")) {
        // Create a Nashorn script engine with specified arguments.
        engine = factory.getScriptEngine(args.toArray(new String[args.size()]));
        // Load initial scripts.
        for (String path : paths) {
        // Invoke users JavaScript init function if present.
        try {
            ((Invocable) engine).invokeFunction("init");
        } catch (NoSuchMethodException ex) {
            // Presence of init is optional.
    public void start(Stage stage) throws Exception {
        // Invoke users JavaScript start function if present.
        try {
            ((Invocable) engine).invokeFunction("start", stage);
        } catch (NoSuchMethodException ex) {
            // Presence of start is optional.
    public void stop() throws Exception {
        // Invoke users JavaScript stop function if present.
        try {
            ((Invocable) engine).invokeFunction("stop");
        } catch (NoSuchMethodException ex) {
            // Presence of stop is optional.
     * Load and evaluate the specified JavaScript file.
     * @param path Path to UTF-8 encoded JavaScript file.
     * @return Last evaluation result (discarded.)
    private Object load(String path) {
        try {
            FileInputStream file = new FileInputStream(path);
            InputStreamReader input = new InputStreamReader(file, "UTF-8");
            return engine.eval(input);
        } catch (FileNotFoundException | UnsupportedEncodingException | ScriptException ex) {
        return null;

To built it you can (cd make ; ant build-fxshell) from within the nashorn repo. The result is in nashorn/dist/nashornfx.jar. To use just java -cp dist/nashornfx.jar <myscript.js> … . For the JDK savvy you can create a launcher by modelling an entry in jdk/makefiles/CompileLaunchers.gmk after the jjs entry.

The big plus for this approach is that it handles almost everything for you. You just have to define a start method with a few class declarations and that is it. The down side is that ideally you would want this implemented as a jjsfx launcher embedded in the JDK. But then we run into the chicken and egg dependency on Java FX.

The second approach only relies on jjs. With a recent modification to Java.extend (currently only in the nashorn forest), it is now possible to subclass javafx.application.Application. and thus launch from within a script. This sounds like all pluses except for the fact you have to wrap your brain around the fact that FX applications take control of execution and has static init dependencies that require careful use in your program.

I prototyped a simple fxinit.js include that shows how we could implement such a scheme. Ignore the implementation quirks. It's simpler than it seems.

GLOBAL = this;
javafx = Packages.javafx;
(Java.extend(javafx.application.Application, {
    init: function() {
        // FX packages and classes must be defined here because they may not be
        // viable until launch time.
        Stage          = javafx.stage.Stage;
        scene          = javafx.scene;
        Scene          = scene.Scene;
        Group          = scene.Group;
        chart          = scene.chart;
        control        = scene.control;
        Button         = control.Button;
        StackPane      = scene.layout.StackPane;
        FXCollections  = javafx.collections.FXCollections;
        ObservableList = javafx.collections.ObservableList;
        Chart          = chart.Chart;
        CategoryAxis   = chart.CategoryAxis;
        NumberAxis     = chart.NumberAxis;
        BarChart       = chart.BarChart;
        XYChart        = chart.XYChart;
        Series         = chart.XYChart$Series;
        Data           = chart.XYChart$Data;
        TreeView       = control.TreeView;
        TreeItem       = control.TreeItem;
        if (GLOBAL.init) {
    start: function(stage) {
        if (GLOBAL.start) {
    stop: function() {
        if (GLOBAL.stop) {
})).class, new (Java.type("java.lang.String[]"))(0));

How you would use it is straight forward. Here is the FX example written for Nashorn;

function start(stage) {
    stage.title = "Hello World!";
    var button = new Button();
    button.text = "Say 'Hello World'";
    button.onAction = function() print("Hello World!");
    var root = new StackPane();
    stage.scene = new Scene(root, 300, 250);;
Note the placement of the load("fxinit.js");. Since this is where the FX Application takes control, anything after the load will not complete until the application exits.

One other quirk. Since you can not static init some of Java FX classes until after the application launches. You can not globally (script level) declare any uses of these classes. Uses can be embedded in methods used after the launch, but no where else. This is a style cramp for me.

There is a third approach I have been considering. It involves some argument trickery, but may play out as a better way of doing things. Imagine jjs fxinit.js -- myscript.js -- my scripts args . The -- indicates the beginning of arguments passed to the script. The notion here is that fxinit.js launches the application and then evals myscript.js. This cleanses my script of any quirks, while putting the onus on getting the command line right.


Saturday Dec 01, 2012

Nashorn in the Twitterverse, Continued

After doing the Twitter example, it seemed reasonable to try graphing the result with JavaFX.  At this time the Nashorn project doesn't have a JavaFX shell, so we have to go through some hoops to create an JavaFX application.  I thought showing you some of those hoops might give you some idea about what you can do mixing Nashorn and Java (we'll add a JavaFX shell to the todo list.)

First, let's look at the meat of the application.  Here is the repackaged version of the original twitter example.

var twitter4j      = Packages.twitter4j;
var TwitterFactory = twitter4j.TwitterFactory;
var Query          = twitter4j.Query;

function getTrendingData() {
    var twitter = new TwitterFactory().instance;
    var query   = new Query("nashorn OR nashornjs");
    query.count = 100;
    var data = {};

    do {
        var result =;
        var tweets = result.tweets;
        for each (var tweet in tweets) {
            var date = tweet.createdAt;
            var key = (1900 + date.year) + "/" +
                      (1 + date.month) + "/" +
            data[key] = (data[key] || 0) + 1;
    } while (query = result.nextQuery());

    return data;

Instead of just printing out tweets, getTrendingData tallies "tweets per date" during the sample period (since "2012-11-21", the date "New Project: Nashorn" was posted.)   getTrendingData then returns the resulting tally object.

Next, use JavaFX BarChart to display that data.

var javafx         = Packages.javafx;
var Stage          = javafx.stage.Stage
var Scene          = javafx.scene.Scene;
var Group          = javafx.scene.Group;
var Chart          = javafx.scene.chart.Chart;
var FXCollections  = javafx.collections.FXCollections;
var ObservableList = javafx.collections.ObservableList;
var CategoryAxis   = javafx.scene.chart.CategoryAxis;
var NumberAxis     = javafx.scene.chart.NumberAxis;
var BarChart       = javafx.scene.chart.BarChart;
var XYChart        = javafx.scene.chart.XYChart;
var Series         = javafx.scene.chart.XYChart.Series;
var Data           = javafx.scene.chart.XYChart.Data;

function graph(stage, data) {
    var root = new Group();
    stage.scene = new Scene(root);
    var dates = Object.keys(data);
    var xAxis = new CategoryAxis();
    xAxis.categories = FXCollections.observableArrayList(dates);
    var yAxis = new NumberAxis("Tweets", 0.0, 200.0, 50.0);
    var series = FXCollections.observableArrayList();
    for (var date in data) {
        series.add(new Data(date, data[date]));
    var tweets = new Series("Tweets", series);
    var barChartData = FXCollections.observableArrayList(tweets);
    var chart = new BarChart(xAxis, yAxis, barChartData, 25.0);

I should point out that there is a lot of subtlety in this sample.  For example;
stage.scene = new Scene(root) is equivalent to stage.setScene(new Scene(root)). If Nashorn can't find a property (scene), then it searches (via Dynalink) for the Java Beans equivalent (setScene.)  Also note, that Nashorn is magically handling the generic class FXCollections.  Finally,  with the call to observableArrayList(dates), Nashorn is automatically converting the JavaScript array dates to a Java collection.  It really is hard to identify which objects are JavaScript and which are Java.  Does it really matter?

Okay, with the meat out of the way, let's talk about the hoops.

When working with JavaFX, you start with a main subclass of javafx.application.Application.  This class handles the initialization of the JavaFX libraries and the event processing.  This is what I used for this example;

import javafx.application.Application;
import javafx.stage.Stage;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

public class TrendingMain extends Application {

    private static final ScriptEngineManager
                                        MANAGER = new ScriptEngineManager();
    private final ScriptEngine engine = MANAGER.getEngineByName("nashorn");
    private Trending trending;

    public static void main(String[] args) {

    public void start(Stage stage) throws Exception {
        trending = (Trending) load("Trending.js");

    public void stop() throws Exception {

    private Object load(String script) throws IOException, ScriptException {
         try (final InputStream is = TrendingMain.class.getResourceAsStream(script)) {
            return engine.eval(new InputStreamReader(is, "utf-8"));
To initialize Nashorn, we use JSR-223's javax.script. 

private static final ScriptEngineManager MANAGER = new ScriptEngineManager();
private final ScriptEngine engine = MANAGER.getEngineByName("nashorn");

This code sets up an instance of the Nashorn engine for evaluating scripts.

The  load method reads a script into memory and then gets engine to eval that script.  Note, that load also returns the result of the eval.

Now for the fun part.  There are several different approaches we could use to communicate between the Java main and the script.  In this example we'll use a Java interface.  The JavaFX main needs to do at least start and stop, so the following will suffice as an interface;

public interface Trending {
    public void start(Stage stage) throws Exception;
    public void stop() throws Exception;

At the end of the example's script we add;

function newTrending() {
    return new Packages.Trending() {
        start: function(stage) {
            var data = getTrendingData();
            graph(stage, data);

        stop: function() {



which instantiates a new subclass instance of Trending and overrides the start and stop methods.  The result of this function call is what is returned to main via the eval.

trending = (Trending) load("Trending.js");

To recap, the script Trending.js contains functions getTrendingData, graph and newTrending, plus the call at the end to newTrending.  Back in the Java code, we cast the result of the eval (call to newTrending) to Trending, thus, we end up with an object that we can then use to call back into the script. 




Technical discussions and status of the Nashorn JavaScript Project.


« July 2014