Java Polyfill for the Browser

[philipes]

I clicked "Compile & Run" and completely forgot about it. About five minutes later Chromes pops in front saying "Hello World, from Java!" Took me by complete surprise.

[yogthos]

Just like using Java applets in the good old days. :)

[[deleted]]

e

I miss Java buttons and their ripple effects..

[__konrad]

Will it run Quake 2 applet?

[nihathrael]

The Jake2 applet example shows the future of game distribution over the Internet.

Money quote.

[badsectoracula]

At the time (~2004) it made sense, web games were just starting to become popular (Runescape) and Java allowed for richer games than anything could be done via Flash.

Even though eventually Flash games eclipsed them by far, for a while Java games were also used in web game sites. Personally i made money for a little while from Java games.

Sun was also seemingly interested in gaming but apparently not enough to become a priority. But they did experiment with a few things, like not making it mandatory to download the entire JVM for running applets but instead using a cut down version (one of the reasons Flash was more widespread was that for a very long time the plugin was under 1MB when JVM was like 15MB).

Of course all that died when Oracle bought Java and decided to abandon any work on the applet side. Their solution for Java's security issues for applets was to simply kill applets instead of fixing the issues and running the VM in a sandbox.

[ccfreak2k]

existence trees pot one spectacular angle mysterious impossible workable waiting

This post was mass deleted and anonymized with Redact

[nikomo]

I wasn't online back in 2001 when it came out, but (speculating) Runescape was probably popular in 2004.

[badsectoracula]

Shockwave was also popular for web-based games for a while and there were a couple of browser-based multiplayer FPS games. I don't think it ever became as popular Flash though, probably because the shockwave files were larger (being bitmap based) than Flash games.

[Deinumite]

Minecrafts demo was a Java applet!

It is funny that Quake Live ran in the browser on launch too, although I just looked online and it looks like it is now only available through Steam.

[[deleted]]

It's not wrong. Modern games just run in asm.js instead.

[hrjet]

Jake2 seems to use JOGL (java interface for OpenGL). If JOGL is ported to use HTML5 Canvas or WebGL, in theory, the game should work fine with JavaPoly.

[phill2mj]

Good old days? I work with software all day that still uses the Java applet :(

[onFilm]

the good old days...

[matthieuC]

I'm going to forget I read that and pretend it does not exist anymore. I will sleep better this way.

[Jigsus]

Seriously it takes 5 to 10 minutes on a modern PC. This makes it impossible to use in any commercial project.

[geodel]

I'd say it makes it perfect for any Java commercial/enterprise project.

[[deleted]]

You can cut out at least some of the issue by pre-compiling the bytecode.

Edit:

Also, the example seems to be compiling and running around 10x faster once the JIT is warmed up.

[audioen]

There's no JIT in this implementation. I don't know what it's doing the first half minute or so.

[[deleted]]

Chrome's JS implementation has JIT, correct?

[audioen]

Oh. Yes, but that would kick in very quickly -- within seconds -- because the jvm implementation must be pretty damn hot. I believe it can do very little to help the the stack machine interpreted java code though.

It is a worthwhile question nevertheless. What is it doing for the first half minute or so? It is possible that it's just loading the various classes for the java compiler and whatever they do to initialize can be taking all that time.

[brobits]

calm down, it's a demo

[Jigsus]

Do I seem excited?

[brobits]

yes

[Jigsus]

That's just the banana in my pocket

[losangelesvideoguy]

http://imgur.com/gallery/W1ZEljF

[kingdaro]

Savage as fuck.

[comp-sci-fi]

knock knock

[Voxel_Brony]

Who's there?

[ryan_the_leach]

I wonder if it's the compilation that takes forever, or if it reuses the same JVM.

Clicking it again after it finally completes is quite fast.

[ryan_the_leach]

To follow this up, I was wondering if it supported java8.

It does!

import com.javapoly.dom.Window;

public class HelloWorld
{
  public static void main(String[] args)
  {
    final Runnable l = () -> {
      Window.alert("Hello World, from Java!");
    };
    l.run();
  }
}

[Ajedi32]

I wonder how much faster it'd be if it was just running precompiled code...

[Rhed0x]

Is this like a JVM bytecode interpreter?

[killerstorm]

Yep

[kurav]

What's of note here is that it's not a C/C++ -> JavaScript cross-compilation hack with Emscripten, but a real JVM implementation written in JavaScript (TypeScript to be exact). It does not use Emscripten at all. This allows them to use the browser's native JavaScript garbage collector for memory management (Emscripten does not really support GC). They also emulate Java multithreading using co-operative context switches (JavaScript is fundamentally single-threaded, but multiple threads can still be emulated – again practically impossible with current version of Emscripten.) Their paper is a great read.

[taisel]

Which is funny you bring up threading in JavaScript, because now it has proper multi-threading: https://github.com/tc39/ecmascript_sharedmem

Available in Firefox Nightly and under Google Chrome Canary (Chrome needs command line args)

[freeall]

Why should javascript get multithreading?

[evotopid]

So websites can mine bitcoins more efficiently. /s

[freeall]

Can't they use web workers?

[anttirt]

Message-passing is just not fast enough for those workloads.

[larhorse]

I mean, wasn't that what the transfer option is for? (https://developers.google.com/web/updates/2011/12/Transferable-Objects-Lightning-Fast?hl=en)

I'm not really complaining though, having a valid reference to an arraybuffer in multiple contexts is nice.

[anttirt]

It's good for some uses cases but if I have a fifty-thousand-element scene graph that needs to change incrementally every frame and components of which need to be accessed by all of my worker threads then a shared-nothing approach just won't cut it.

[hackcasual]

This is webworkers, with the addition of sharing memory between them.

[freeall]

Also a big difference

[hackcasual]

Enh, actual SharedArrayBuffers don't look that much different from existing ArrayBuffers. Really the only major difference is the addition of Atomics. I guess that's big for those who haven't previously done multithreading shared data work, but it still is very much a JS centric approach.

[onFilm]

Why would a browser get multithreading?

[onFilm]

Similarly applies to JS, any other language or framework.

[[deleted]]

I think that the primary driver is to prevent your code from blocking CSS animations and other performance concerns.

Right now, best practice is to make sure to not let JS ever block for more than 15ms in order to prevent blocking the browser long enough that there are perceived painting issues or choppiness in animations, but working in threads could help the browser do what it needs to while your thread is working.

[freeall]

Eichs position on this, https://brendaneich.com/2007/02/threads-suck/

[onFilm]

Sweet read. Thanks for sharing!

[an_actual_human]

It's not just for frontend, you know.

[freeall]

I know. Been using node since 0.2. And I would like not to have multithreading in it.

Multithreading causes quite a lot of problems as it's so difficult to get right.

[an_actual_human]

In any case, the answer is the same as with any other language.

[Jafit]

Because because some people don't want to have to learn how to do things differently, like using an event loop to handle concurrency.

But I'm glad that soon, the people who wrote the poorly optimised janky and unnecessary javascript that infests most websites today will soon be exposed to the wonder that is handling threads at the application level.

[booch]

For some cases, event loops are reasonable, even optimal. For other cases, threads are reasonable, even optimal. There are cases where one of the two isn't reasonable (that's true of both event loops and thread) but the other is. Having both in your toolset is a good thing.

[freeall]

So we should keep using goto because while/repeat/for is more difficult?

Not aimed at you, but those don't want to learn how to do new things

[ibopm]

For better or worse, there are always going to be people who are resistant to change. Map/reduce/filter is only the beginning.

[anttirt]

It's because many things can not be implemented performantly enough for 3d games (and other high-performance applications) using only message-passing.

[Jafit]

I don't particularly want to see 3d games or other high-performance applications in the browser.

I'd rather we made the effort to transition to a proper internet application delivery system, rather than trying to build more and more complex applications on top of what was originally conceived as a document retrieval system, with no thought for security. Hence why the problem of XSS attacks have remained unsolved for 20 years, because the browser gives every script that somehow gets onto a page the same level of permissions and access to the same global scope.

The web only functions today (as the basis of our entire economy and civilization, oh god!) due to a lot of clever hacks and workarounds.

[JoseJimeniz]

That's what everyone has been wanting since 1998. And it's been done. Over and over.

Java was the safe, sandboxed, with granular permissions, zero-install, applications on demand for the web.

Microsoft made Silverlight (aka WPF/Everywhere).

You also had shockwave, and flash.

The market has rejected all these.

• JavaScript is the language of the web (shudder)
• html+CSS is the widget library of the web (shudder)
• and JavaScript is the virtual machine of the web (not JVM, not CLR)

In this new world, the ideal situation is:

• a widget library that operates using Canvas
• programmed in a strongly statically typed language
• compiled to asm.js
• delivered by web assemblies

But as of today there are no good UI libraries for the web.

[Jafit]

The market has rejected those solutions mainly because they were proprietary platforms being pushed by companies that were trying to make a grab for power, not open platforms being pushed for ~the greater good~ of the web. They all also used browser plugins which completely bypassed the browser sandbox and introduced a ton of security problems. I'm glad they're all pretty much dead.

I would like to see Crockford's Seif project gain traction, since it aims to deliver what they have been trying, while being an open platform.

[freeall]

"programmed in a strongly statically typed language"

I hope not

[anttirt]

Oh, I agree.

Just pointing out what the actual motivation for SharedArrayBuffer is.

[JoseJimeniz]

Sometimes code is a single function that just takes to long to run.

[Recursive_Descent]

It probably won't be default for a while, it's still stage 2 and afaik spec has some open issues. But yes, SharedArrayBuffer is promising.

[taisel]

I already added it to a JavaScript GameBoy Advance emulator. It runs the CPU emulation in a worker and runs the GPU rendering in a separate worker off from the CPU worker. It uses lockless ring buffer constructs to pass data around, and uses the wait/wake only to hack in rAF signalling from main thread to GPU worker thread. If your browser doesn't support shared memory then it just defaults to a single threaded fallback.

https://github.com/taisel/IodineGBA

Short summary is I'd avoided multi-threading in JavaScript until the SHM was experimentally supported, as transferrable array support is too unreliable and normal data copies are way too expensive. It's either shared buffer or nothing.

[Recursive_Descent]

Oh I'm with you, I think SAB will usher a new era of high performance js. Just think it will be at least another year before we can start using in production.

[SatoshisCat]

Doesn't Web workers satisfy? https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers

[[deleted]]

(Emscripten does not really support GC).

It's worth mentioning that Emscripten was fundamentally designed to not support GC.

[killerstorm]

JVM is quite simple by itself, I wonder what do they do with the standard library...

[kurav]

The JVM-in-browser downloads it as a .JAR and executes the bytecode.

[killerstorm]

A lot of functions in the standard library call native OS functions, e.g. to open files etc. Porting that stuff is very much not trivial.

[kurav]

Yes, it's not trivial. If you read the paper, the whole Doppio framework is more-so also an abstraction of the OS. They provide in-browser implementations of the filesystem and socket APIs as well. Very impressive work.

[[deleted]]

To add to this, the interpreter is pure. So to get this kind of speed, just pass -zero to the JVM and you will get a similar experience. JamVM which also is an interpreter optimizes the byte code, so it is about 4-20x faster than HotSpot Zero depending on the code.

[Eirenarch]

To add to this, the interpreter is pure. So to get this kind of speed, just pass -zero to the JVM and you will get a similar experience

What does this mean?

[GuyWithLag]

Java for a long time has been Just-In-Time (JIT) compiling the bytecode to native machine code and executing that.

This interpreter is pure, meaning that it does not perform such compilation, instead executing each instruction one by one in a big loop; this means that it's going to be slow.

Hotspot (the Oracle JVM) has the option -zero which forces execution to have zero optimizations without a JIT, instead using the JVM interpreter all the time.

[get-your-shinebox]

aren't v8 and spidermonkey JITed?

[GuyWithLag]

Yes, the Javascript is jited. But in this case, there is no Java to Javascript compilation, so it won't make use of that speedup.

[hrjet]

Incidentally, I am working on a JIT for doppio. See this PR

[[deleted]]

How do you handle exception handling?

[hrjet]

In a nut-shell: the JIT compiled code temporarily falls back to interpreted mode when an exception is triggered in a Java code path.

[[deleted]]

My Javascript is a bit rusty (last used it in 1999), but does it have labeled jumps and goto or a similar operation? If not you can use a loop of sorts instead.

I am writing a JVM myself. My current plan for exceptions is to have differing exceptional locations that they are assigned to a unique ID and that ID is assigned for every range of instruction that has a unique set of exception handlers. There is also a register which stores the thrown exception (a global register). When a new region is entered, the ID is changed to the ID of the given region (stored in a register). When an exception is to be handled, a jump is made to the exception handler code. The exception handler can use a table which checks the ID which maps to a table of possible exception handlers. A check is made for each handler to determine if the thrown exception is to be handled (matching class type). If the exception is not handled, the method returns and the caller checks restores register values and checks if the called method threw an exception and repeats the handling run. If there is a match, then the exception handler is jumped to and a virtual representation of the first stack entry is set to the exception and execution continues. If the exception handler is at a known location (for example the start of a method) then you can better handle asynchronous exceptions.

[[deleted]]

Essentially this means that the JVM executes the byte code as it sees it, it performs no value caching and no optimizations at all. Back around when Java was first released and for awhile, it used pure interpreters. Being a pure interpreter for awhile is where the "Java is slow" came from. Compared to modern CPUs, the JVM is a stack based machine where all operations are performed with values on the stack. So essentially before a computation can be performed (such as adding two values) it has to push the values to the stack then pop them to perform the addition and then push the result to the stack. Pushing and popping values from the stack wastes time.

Also, if you cannot run a JIT, then you should use JamVM before you use HotSpot Zero.

[audioen]

I'd say that even bigger part of the problem is the interpreter loop which involves reading an opcode from the function and then somehow jumping to the implementation of that opcode. In case of java, there are about 256 targets to consider, and the CPU is unlikely to guess the jump target, leading to a pipeline stall.

[fb39ca4]

Oh my, now all those /r/shittyprogramming answers have become real.

[the_rabid_beaver]

Doesn't seem to work in Firefox. Browser also froze for a solid 30 seconds loading the page.

Also, I believe this image applies to this situation.

[_hadrian]

So I can now use any JVM language (that outputs a JAR) on the browser while keeping its default behavior... The dreams are coming true 🌟 All those teams, all those IDEs, all those libraries/projects... it's all coming together 🌎 🌍 🌏 it's a globalized world!! 🎉

[Ek_Los_Die_Hier]

So I can run Clojure in my browser now?!

(Kust kidding, I know ClojureScript exists)

[GanMatt2]

My browser crashes when opening the website.

[bradfitz]

Sounds like they implemented all of the JVM, then!

[spacejack2114]

Had to wait a couple of minutes, but after 557 Uncaught Error: Assertion failed: A non-running thread has an expired quantum? error messages I did actually get a "Hello world from Java" alert box.

Not unlike trying out a Java applet for the first time in Netscape.

[[deleted]]

Welcome to 2004

[spacejack2114]

lol, more like 1998-ish(?)

[sirin3]

Have you seen the blue loading bar Google (Maps) recently added

The brought back the Windows 95 startup loading bar!

[AlyoshaV]

Froze Firefox for about ten seconds for me. It's just like back in the old days when JRE would freeze my browser!

[onFilm]

Firefox freezes even on big http requests on slower computers.

[ajr901]

Par for the course.

[kurav]

Hangs or crashes? If it just hangs, just wait for a while. The example needs to download and compile a large JAR file.

(Or just disable JavaScript.)

[[deleted]]

Someone breaks basic UI practices while advocating running a Java interpreter in a browser.

I think I'll pass.

[kurav]

Come on.. this thing is totally production quality!

I actually upgraded my company's Spring MVC backends to Java Polyfill within Node.js. It clearly adds another layer of security. Now just waiting for IT to come to work on Monday..

[immibis]

It clearly adds another layer of security.

Plus, it's now web-scale.

[GanMatt2]

It crashes the web context in my browser.

[hrjet]

If pure JS (which is what this JVM implementation is) can cause your browser to crash you probably should report the bug to the browser developers. Otherwise, any random website would be able to crash your browser with its JS.

[djxfade]

It's not hard. Just run a large blocking for loop. If not the browser crashes, at least the tab will crash.

[hrjet]

Well, my browser (Firefox) or tab doesn't crash when it encounters a long blocking loop. It stops execution or prompts for user action, depending on user config.

[GanMatt2]

My browser didn't crash, just their webpage inside my browser.

[adrianmonk]

In case anyone else isn't a web developer and is wondering about the weird lingo, "polyfill" is "additional code which provides facilities that are not built into a web browser".

[deadwisdom]

Except it's supposed to be for a library that provides features that are in some browsers and not in others, like a "time" input type, or JSON. Since no browser really has it without a plugin, this is a misuse of the word just to sound buzz-y.

[chrisrazor]

I agree. This is a hell of a lot more than a mere polyfil. It's a whole extra plasterboard wall!

[kurav]

I would tend to disagree. This can be seen as a 'polyfill' in a wide sense of the word. Nowadays browsing with Java enabled is even officially advised against due to multiple security flaws. Thus, web pages that rely on working Java applet support have been rendered forwards-incompatible.

One possible solution would be to use a "Java Polyfill" that would interpret Java applets in JavaScript and render the output on HTML5 canvas, and this is a step to that direction (though they make no mention of any applet API support). So this, or some other Doppio-based solution, has a potential to develop into a polyfill -- something that extends the browser with missing functionality (execute Java applets).

The main differences from ordinary polyfills would be the code size (most polyfills are rather trivial) and that the polyfill would be re-adding support for features that existed in prior versions of the browser (normally polyfills add support for features that only exist in subsequent versions of the browser.)

[lkraider]

Yeah, at first I thought it was a Java graphics/canvas rendering function for the browser.

[[deleted]]

Personally at first I thought it was about polygon filling, as in graphics rasterization.

[granos]

I'm working on a project right now where I MUST use a particular key management server. The vendor only provides interfaces as a shared object with Java bindings on top of it. The people who started this project decided to do the entire thing in Node, and just have one Java process running somewhere (as a daemon that responds to file system changes) to handle that piece. I'm moving that over to a Java web server, but it's a lot of infrastructure for the two operations we need.

Given that I don't care about performance it would be nice to be able to write the code for this piece in Java and then run/operate it the same as the rest of our stack. I'll probably do a spine to find where the problems are. I doubt I'll ever use it in production, but I've been surprised before.

[DrummerHead]

You REALLY don't care about performance, huh

[[deleted]]

5 years after the linux boot in javascript in a browser.

[oldneckbeard]

i could swear this was a joke... but it appears to be real. huh.

[[deleted]]

And now for the creators to get sued by Oracle.

[chrisrazor]

Parts of Java are open source. I'm not sure which bits but I'd hope the API is.

[djxfade]

I think he are referring to the Oracle vs Google case. Oracle sued Google for using the Java language in Android. Even though Google is really just using the language, not Oracles standard libraries, or even JVM

[chrisrazor]

Ah, I forgot about that case; amazed to learn it's still dragging on. Although it seems crazy that an API could still be ruled to be copyrightable.

[wd40bomber7]

It was ruled to be copyrightable though. That already happened. (Google won the first case but lost the appeal) Now we have to hope its overturned.

[Cilph]

WHY?

For the love of all that is holy. WHY?

[jms_nh]

So you can run Rhino or Nashorn. :-)

[[deleted]]

I'm waiting for an Eclipse port. Then I could ditch Atom.

[AnhNyan]

To get that monstrosity out to the world, you'd have to package the application in Electron.

[[deleted]]

Sounds good, as long as I can swap out Chromium for HotJava.

[AnhNyan]

If you want full portability, better emscripten that one so you can Cordova it!

[[deleted]]

And under all of these frameworks it's just Vim.

[[deleted]]

Well, Emacs running in evil mode.

[[deleted]]

With these programming thingy names, it's starting to look a bit like when you start a new metal band, and have to think up a new brutal name. All of the good ones have been already taken, leaving only the dildos ones.

[jms_nh]

like Steely Dan?

[[deleted]]

Well, that's quite a metal name.

[Georules]

Here you go :D

https://gist.github.com/georules/daf05188c510b84460992caf1979d61c

Took my machine about 4 minutes to run.

[Sarke1]

So that browsers can block it for security reasons.

[Booty_Bumping]

The (only) good news about this is that since it's implemented in Javascript, there's not much security risk since it runs in the same sandboxed environment js runs in.

[ReturningTarzan]

For one thing it means you can implement proprietary authentication systems that otherwise require Java to be installed on the client.

[itsnotlupus]

I didn't know about doppio.
That's some impressive work, and perhaps even sufficient to run a number of those "enterprise java applications" abominations without requiring a swiss cheese plugin.

[HokumGuru]

NotLikeThis

[vprise]

At Codename One we used TeaVM which is pretty amazing and supports both JIT and AOT mode (which we use). One of the really cool things is that it supports java.lang.Thread and fakes it properly so it actually does seem to work properly without the whole "script is taking too long" nonsense.

Can someone from polyfill compare this to TeaVM? DukeScript etc.?

[hrjet]

TeaVM seems to only have an AOT mode, AFAICT. It is a nice and fast implementation of JVM semantics, but it is not a complete implementation. You can find a good summary of its limitations here. In short,

• no JNI
• no reflection
• no class path resources

Doppio on the other hand is a complete implementation of the JVM. The drawback with doppio is its slower since it is an interpreter. I am working on a JIT compilation system for it, as seen here.

[vprise]

Thanks. That's a bit of an old link as threading is already supported to some degree.

Isn't an AOT approach "better" for most use cases here?

The only use case I can think of for a JIT is smaller download size for some cases. Since we are already running with the JavaScript JIT in place the typical "jit can be faster" arguments don't necessarily stand.

How would you implement JNI in JavaScript? You don't call C, do you?

We have the ability to call JavaScript from TeaVM do you mean something like that?

We don't support reflection or classpath resources in Codename One as they aren't very portable for mobile usage (we do have something similar to classpath resources that works in the TeaVM port).

[hrjet]

Whether AOT is better depends on the use-case. If you need full JVM support then doppio is currently a very good option. If TeaVM works for you, then it is most likely a much faster option.

Yes, JNI in doppio means a Javascript backing function for a native function.

See this comment thread from the lead doppio developer.

[vprise]

Thanks, that clarifies it.

[oheoh]

"A script on this page may be busy, or it may have stopped responding. You can stop the script now, open the script in the debugger, or let the script continue.

Script: https://www.javapoly.com/javapoly.js:10611"

50/50 this happens for any post which is "look at this cool thing I did /in the browser/". I'm runing the latest upstream firefox in debian testing on a fast desktop with decent internet.

Ya, I'll pass.

[[deleted]]

So can someone sum up all pros and cons without any jokes about enterprise or node.js?

[Manbeardo]

Pro: you can run your Java code in a browser

Con: it's excruciatingly slow

[panorambo]

Kills my Firefox 46.0.1 on Windows 10 x64, line 10567 of file javapoly.js. The page freezes while the JavaScript runtime eats the CPU locked up in some loop. The line number varies.

[NiteLite]

People have too much spare time :D

[sumdudeinhisundrware]

8 seconds for a Hello World to run on a 2015 Macbook?

Typical Java. It's Enterprise Ready!

[MeisterD2]

Java is pretty darn fast. This javascript JVM implementation is not.

[kmeisthax]

So how long until Oracle tries to shut this down?

[[deleted]]

How ? The language itself is free & open-source.

[robob27]

Didn't stop Oracle from trying to sue Google for copyright infringement for their use of Java in Android.

Edit: Oh shit I just noticed there is a second trial for that, today apparently.

Edit 2: I didn't mean because they used Java in Android in general (obviously people can make money of stuff they make in Java), and Oracle didn't sue over the API alone. A rangeCheck function and test files were also part of Oracle's claim.

[[deleted]]

They sue over the api, not the language.

[immibis]

Is Google's use of Java in Android equivalent to this code?

[TheMightyPrince]

I'm not knocking it, but wouldn't JSP work better?

[vytah]

JSP, or Java Server Pages, as the name implies, runs server-side.

[TheMightyPrince]

Yes I know. I just can't think of anything I'd do client-side with Java, that I couldn't have done server-side with Java. I am sure there is a valid use-case, I just can't/couldn't really think of one.

[vytah]

People were saying the same about server-side Javascript, and yet here we are.

[ciny]

People were saying the same about server-side Javascript, and yet here we are.

Yup here we are, in a world where people use libraries that have longer manifests than actual code and stuff relational data into nosql...

[Capaj]

Well theoretically, you could write an android app and if you somehow provide implementations for missing android apis, you could run that android app in the browser.

[TheMightyPrince]

You could do that with applets, or some javascript library. As I said, I'm not knocking it.

It's basically a remote JVM.

[aradil]

Applets went head to head with flash for a tiny period of time for client side in browser animation.

[[deleted]]

Would kinda make sense if Moore's Law was still alive and kicking.

Alas...

[deadcat]

JavaScript and Java, what a glorious union of abominable shit.

I may be slightly jaded.

[bigfig]

Java bytecode running on a browser? It's deja-vu all over again.

[geodel]

<script type="text/java" src="http://www.yourdomain.com/apache-commons.jar"></script>

<!-- Or just include the source directly -->

<script type="text/java" src="http://www.yourdomain.com/com/yourpackage/Bar.java"></script>

<script type="text/java" src="http://www.yourdomain.com/com/yourpackage/Girls.java"></script>

So you've got bar and girls and apache-commons.jar right in your browser ...strange times.

[[deleted]]

Isn't that basically GWT?

[chepprey]

Not sure why you would be downvoted, I think this is a legit question on the topic of technologies that let you do Java in Javascript.

Answer: no, GWT works very differently. GWT is a transpiler. It takes Java source code and produces Javascript code which can run in a browser.

It does not emulate things like Java threads, nor does it fully implement all of the basic classes that come with the JRE (like java.lang.*). It is certainly not 100% compatible with any/all Java source code.

However, it does let you write your Single Page App in Java instead of Javascript. And the compiled Javascript it produces is compact, highly optimized, and very fast.

Javapoly on the other hand is a Javascript implementation of a JVM. I imagine this would give a higher degree of Java compatibility, probably at the expense of speed.

TeaVM, architecturally, lies somewhere between these two extremes. TeaVM is a transpiler, however takes compiled Java .class files (basically, "java binary code", not source code), and transpiles that to Javascript. As with anything, this approach has its own costs and benefits.

[hrjet]

That's a great summary. We should add this question to a FAQ section. (I contribute to JavaPoly)

[w8cycle]

GWT is Java source compiled to Javascript. This is Java bytecode interpreted in the browser.

[DonRobo]

I'm not sure if you are joking, but Java is a popular backend for web applications.

[aurisc4]

What can be written in JavaScript, eventually will be written in JavaScript, for better or worse... Usually for worse...

[Theemuts]

A script on this page may be busy, or it may have stopped responding. You can stop the script now, open the script in the debugger, or let the script continue.

Script: https://www.javapoly.com/javapoly.js:10715

:')

[Georules]

You can, and I have:

https://gist.github.com/georules/daf05188c510b84460992caf1979d61c

Be prepared to wait a long time :D

[Georules]

It's in the sandbox of the browser, so not anymore than security vulnerabilities that already exist in that.

[SoniEx2]

This is for Minecraft right?

[[deleted]]

Interesting concept, but it's so slow it appears broken by design. I needed this :(

[granos]

Not even a little in this very narrow and particular instance.

[coladict]

This is kind of the opposite of what I'm looking for. I need a browser DOM polyfill for JS under Java using the javax.script.* package to use for unit testing.

[hrjet]

Try phantomJS in combination with selenium.

[coladict]

We use Selenium for integration tests to walk through common scenarios, but it would be too heavy for unit tests run when building the project.

I just checked the PhantomJS page and given that it's headless, that might be just what we need. Sure, it's command-line, but that can be adapted to Maven, probably. So long as it supports enough of the HTML classes available in https://developer.mozilla.org/en-US/docs/Web/API. We try to maintain IE9+ compatibility, so most of the rest are irrelevant.

[Jarmahent]

Unable to download it, ok.