April 28th, 2008
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When I was in Tokyo this past fall speaking at the Shibuya.JS user group I had the opportunity to see a number of interesting JavaScript projects that have yet to make it outside of Japan.
One project, in particular, really caught my eye. It's called Orto [PDF, Japanese] and is an implementation of the Java Virtual Machine (JVM) in JavaScript. This means that you can take an existing Java application, compile it to bytecode, run it through Orto (which produces the JavaScript, and embed it in a web page. While it doesn't provide the full capabilities of most Java code it does provide enough to make for some interesting demos.
The one demo that was presented was that of a real-time, interactive, Tetris game:
If you take a peak at the generated source code you can see some interesting tidbits (obviously all of the code is meant to be 'machine readable' - being just converted bytecode):
"java/lang/Thread 1316742099":function(){var orto333=orto245[0];
var orto336=orto350(orto333);
if(orto336.orto340!=orto310){orto223("java/lang/IllegalThreadStateException",null);
return ;
}
case 117:orto246[orto247-2]={high:(~orto246[orto247-2].high)
&0xffffffff,low:(~orto246[orto247-2].low+1)&0xffffffff};
if(orto246[orto247-2].low==0){orto246[orto247-2].high++;
orto246[orto247-2].high&=0xffffffff;
orto246[orto247-2].low=0;
}break;
case "CHECKBOX":orto171=orto188["orto/ui/CheckBox"];
break;
case "IMAGE":orto171=orto188["orto/ui/ImageButton"];
break;
case "RADIO":orto171=orto188["orto/ui/RadioButton"];
break;
Unfortunately, the information on the subject is a little scarce (considering that both orto.accelart.jp and orto.jp seem to be missing any relevant information). There are a couple of things that are apparent, however:
- The result is able to handle threaded application code (translating the threads into a series of yields with setTimeout (mentioned in the presentation and demonstrated in the Tetris example).
- The application can use regular Java conventions for designing and constructing the UI (as shown here, as well). User Interface components are translated to, similar, HTML ones. It's not apparent to what extent functionality is implemented, but it is to a certain degree.
- Keyboard interactions are able to be handled and translated to normal Java callbacks.
I was especially pleased with the resulting performance of the demo application. I wasn't expecting a game (translated multiple layers deep) to still be as playable as it is. Obviously the culmination of JavaScript optimization and increases in browser performance have served these types of endeavors well.
Tags: java, javascript, jvm
25 Comments on 'Running Java in JavaScript'
August 8th, 2007
After yesterday's post on the browser scripting revolution, detailing the new projects being built on top of Tamarin, a number of questions came up concerning the choice of Tamarin instead of other virtual machines. Two engines came up, in particular: The Java Virtual Machine (JVM) - which is already able to run Jython and JRuby, and Mono - which is able to run IronPython and IronRuby.
I'll defer to the words of Mike Shaver and Brendan Eich to explain the reasons as to why, though in a nutshell: The non-technical reasons for choosing Tamarin are over intellectual property and licensing issues and the technical issues are related to compilation speed, file size, and memory footprint.
Mike Shaver:
Here are a few, at least as I see them:
* Optimized to run JavaScript and sibling languages, which is our most important language target by a vast margin.
* Licensed appropriately.
* About 1/25 the size, I think (200KB for Tamarin, 5MB for Mono as described by Miguel elsewhere)
* In my coarse measurements, significantly smaller memory footprint.
I was once quite a supporter of getting Mono into our world, including writing a prototype XPCOM binding for it, but I didn't see a path to getting the important factors (performance, licensing, footprint in code and memory) resolved, and I don't think it's much closer today. Nobody in Mono-land was interested enough to contribute to that, which is another counterpoint with Tamarin I suppose, where we have very active contributions from Adobe and others to help us get it in the state we need for it to be a suitable basis for building our whole app on.
It's not like we didn't look hard at Mono, and in the case of many of us lobby hard for licensing and patent concerns to be swept aside. Tamarin is a very good fit for us in a large number of ways, unfortunately including a number of ways in which Mono is not.
Brendan Eich:
Moreover, for Mozilla at least, we absolutely cannot depend on closed source, and we require a non-copyleft BSD license, or at most MPL/GPL/LGPL. Java was not even open source until recently (I don’t remember the date; it was preannounced one too many times :-/), well after we had to make our own plans and commitments.
Finally, in spite of the prospects with JRuby, the JVM really is about Java first and last. Tamarin is about an ECMAScript variant, so it’s a better target now, and more likely to evolve to support JS1 and JS2 in a first class way, than the JVM.
Compilation heroics can help, but the browser will remain an environment where compilation must be very fast. Wherefore our forthcoming work on a trace-based JIT.
Tags: vm, tamarin, mozilla, javascript, mono, ecmascript, java
11 Comments on 'Why Tamarin instead of...'
July 9th, 2007
This weekend I took a big step in upping the ante for JavaScript as a Language. At some point last Friday evening I started coding and didn't stop until sometime mid-Monday. The result is a good-enough browser/DOM environment, written in JavaScript, that runs on top of Rhino; capable of running jQuery, Prototype, and MochiKit (at the very least).
The implications of this are phenomenal, and I'm not the only one who's interested in it what this could mean for server-side JS development. More on that in a minute, but first here's some sample results from running jQuery:
jQuery
$ java -jar build/js.jar
Rhino 1.6 release 6 2007 06 28
js> load('build/runtest/env.js');
js> window.location = 'test/index.html';
test/index.html
js> load('dist/jquery.js');
// Add pretty printing to jQuery objects:
js> jQuery.fn.toString = DOMNodeList.prototype.toString;
js> $('span').remove();
[ <span#å°åŒ—Taibei>, <span#å°åŒ—>, <span#utf8class1>,
<span#utf8class2>, <span#foo:bar>, <span#test.foo[5]bar> ]
// Yes - UTF-8 is support in DOM documents!
js> $('span')
[ ]
js> $('div').append('<span><b>hello!</b> world</span>');
[ <div#main>, <div#foo> ]
js> $('span')
[ <span>, <span> ]
js> $('span').text()
hello! worldhello! world
On a whim, I then plugged in Prototype and MochiKit, both of which appeared to work OK (I haven't done any significant testing with them - so there's probably gaps). Here's some sample results:
Prototype
$ java -jar build/js.jar
Rhino 1.6 release 6 2007 06 28
js> load('build/runtest/env.js');
js> window.location = 'test/index.html';
test/index.html
js> load('prototype.js');
js> $$('div p')
<p#firstp>,<p#ap>,<p#sndp>,<p#en>,<p#sap>,<p#first>
js> Object.toJSON({foo:'bar',baz:true});
{'baz': true, 'foo': 'bar'}
js> var fn = (function(name,msg){
print(name + ' ' + msg); }).curry('John');
js> fn('hello!');
John hello!
MochiKit
$ java -jar build/js.jar
Rhino 1.6 release 6 2007 06 28
js> load('build/runtest/env.js');
js> window.location = 'test/index.html';
test/index.html
js> load('Mochikit.js');
js> $$('div')
<div#main>,<div#foo>
js> document.body.innerHTML = '';
js> document.body.appendChild( P( 'test',
A({href:'http://google.com/'}, 'link')) );
js> document.body.innerHTML
<p>test<a href='http://google.com/'>link</a></p>
js> $$('a')
<a>
I just want to emphasize that these are un-modified copies of jQuery, Prototype, and MochiKit - all running perfectly in this un-natural environment.
When I came up with this idea for an environment, I was mulling over a couple ideas: Namely, better ways of automating tests and ways to bring JS-style DOM/HTML interaction to the server-side. Having a way to bring this popular idiom to established problem sets seemed like a lot of fun.
In short, the following (at the very least) can all get a big dose of JavaScript:
- Automated Testing
- Screen Scraping
- Web Application Development
Now, if you think I'm crazy, I'd like to show you a couple quick examples:
Automated Testing
$ java -jar build/js.jar
Rhino 1.6 release 6 2007 06 28
js> load('build/runtest/env.js');
js> window.location = 'test/index.html';
test/index.html
js> load('dist/jquery.js');
js> load('build/runtest/testrunner.js');
js> load('src/jquery/coreTest.js');
PASS (1) [core] Array.push()
PASS (2) [core] Function.apply()
PASS (3) [core] getElementById
PASS (4) [core] getElementsByTagName
PASS (5) [core] RegExp
PASS (6) [core] jQuery
...
Oh yes, that's right - the full jQuery test suite is now automated and capable of running in Rhino (passing all tests). jQuery served as my initial testbed for development, making sure that I was getting all of my code right. So if you import a copy of jQuery into this environment, it should work "just fine".
By the way, you can try out the automated test suite by getting a copy of trunk/jquery out of SVN, then running make runtest - the results are just awesome.
Screen Scraping
This is one part that works pretty well right now - with the huge caveat that it only works on well-formed XML documents (oops!). I'll be integrating an HTML parser into the code base so that we can make this functionality a little more resilient. In the meantime, here's an example of the sort of scraping that you can do currently:
load("env.js");
window.location = "http://alistapart.com/";
window.onload = function(){
load("dist/jquery.js");
print("Newest A List Apart Posts:");
$("h4.title").each(function(){
print(" - " + this.textContent);
});
};
And here's another one that writes the results out to a file:
load("env.js");
window.location = "http://alistapart.com/";
window.onload = function(){
load("dist/jquery.js");
var str = "Newest A List Apart Posts:\n";
$("h4.title").each(function(){
str += " - " + this.textContent + "\n";
});
var out = new XMLHttpRequest();
out.open("PUT", "file:/tmp/alist.txt");
out.send( str );
};
Oh yeah, I went there - I made PUT and DELETE requests to local files perform the expected actions. I think the result is hilarious.
Web Application Development
This is still a work in progress, but some of the initial ideas are already at play here in this environment. When I have some time I plan on making a JavaScript-based web app framework out of this - which should be pretty cool.
Here's some psuedo-code for how I think it could work:
window.onload = function(){
print("Content-type: text/html\n");
if ( location.href == "/" )
show_home();
print( document.innerHTML );
};
function show_home(){
document.load("index.html");
document.getElementById("time").innerHTML = (new Date()).toString();
}
Download!
Check out the code - there's still huuuge gaps of functionality missing - I only implemented the bare minimum to get this environment working (and passing the jQuery test suite). So your mileage may vary.
Download: http://jqueryjs.googlecode.com/svn/trunk/jquery/build/runtest/env.js (Formatted)
How to Use
To start with, you'll need to have, at least, Rhino 1.6R6. You can download it from Mozilla FTP.
Now download the env.js script and put it in the same directory as the Rhino js.jar.
In order to use it from the command-line, you'll wanna do something like this:
$ java -jar js.jar
js> load('env.js');
js> window.location = 'some.html';
some.html
js> // Your code here!
It's important that you do window.location = "some file" before loading any DOM-dependent code (as the 'document' object doesn't exist before the location request).
A full list of Rhino-shell-specific commands can be found in the Rhino Shell docs.
If you want to write executable scripts, the contents will look something like this:
load('env.js');
window.location = 'some.html';
window.onload = function(){
// Your code here
};
Which can then run like so: java -jar js.jar myscript.js.
Feedback is very much welcome - I've only thought of a couple use-cases thus far, but I'm sure that the surface is just being scratched.
Tags: rhino, java, ecmascript, firefox, mozilla, javascript
61 Comments on 'Bringing the Browser to the Server'
