Is there a Java byte code reader implemented in javascript?

Question

I know there are lots of libraries that read byte codes that are written in Java. Does someone know of a byte code library that is implemented in Javascript?

Answer 1

Since javascript is typically run inside a browser, it generally cannot read the actual bytes out of files, which makes it less-than-ideal for reading java bytes. If you somehow got the byte codes encoded in a form that the javascript could read, what would you expect the library to do with it? Can you provide more details about what you're trying to do?

If you're looking to be able to write code in Java, and have it run inside a browser, take a look at GWT. It uses Java to recompile your byte-code into optimized javascript.

Edit

Based on your added comment, that you are hoping to "find out the classes and methods used in a jar file on my local disk":

Since javascript is unable to access files on a local disk (at least, without using ActiveX), the technology simply won't allow for this sort of thing. Is there a reason you wanted to use javascript for this, rather than java?

And please accept my apologies if it sounded like I was questioning your motives. I really just wanted to get enough information to be able to adequately answer your question.

Answer 2

Update:

It looks like the Japanese project I tried to link to below is long gone. In any case, time has passed and now there are a couple of hits for "jvm in javascript" on Google. Namely:

• Doppio
• BicaVM

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Look what I found:
http://ejohn.org/blog/running-java-in-javascript/

Does this help?

Edit: unfortunately it looks like the original project's site is dead.
You could try through the Web Archive, here (in Japanese, tried to Google translate it, but I guess it was too much indirection :))

For goodness sake, if you follow that link, run your download through an anti-virus.
I don't know if it's trustworhty.

Answer 3

There are compilers which can compile Java to JavaScript. As a last resort, you can use one of those compilers to take a JVML bytecode disassembler written in Java and compile it to JavaScript. One example of such a compiler is GWT.

Similarly, there are compilers which can compile JVML bytecode to JavaScript. Again, you can take one of the above JVML bytecode disassemblers written in Java, use any Java-to-JVML compiler (javac, ecj, gcj, …) to compile it to JVML (i.e. .class files), then compile those .class files to JavaScript.