From: Jason Foreman <threeve.org@...>
Date: 2005-06-22T00:08:37+09:00
Subject: Re: Ruby and Java

On 6/21/05, Wayne Pierce <shalofin@gmail.com> wrote:
> I have a vendor product with Java APIs that I need to write against
> and would like to use Ruby.
> 
> Does anyone have an opinion on the most reliable way to interact with
> Java from Ruby?  I've seen some different projects, but can't tell if
> there is any major difference between how they are implemented or
> which are actively maintained.
> 
> Thanks,
> 
> Wayne
> 
> 

Two main options:  RJB [1], and JRuby [2].  

RJB (RubyJava Bridge) is an extension to the standard Ruby interpreter
that lets you communicate with a Java VM via JNI.  It works pretty
well, but can be a bit 'low level' sometimes, due to the nature of its
implementation.  IE, sometimes you need to know how to construct java
method signatures and such (not a big deal)

JRuby is a complete Ruby interpreter written in Java, so all your Ruby
code runs in the JVM.  This has advantages that the classes can have a
tighter relationship, however the implementation is currently a little
slow, and partially incomplete.  Also, you lose the ability to use
Ruby libraries and extensions written in C.

I've used RJB for a project in order to use the JasperReports library,
and had pretty decent success.  It can be difficult to do proper error
handling, because you have both Ruby errors and Java exceptions to
deal with.  But it is certainly feasible.

It works best when you simply want to call some java code from ruby,
and get the result.  When you start wanting to have ruby classes
inherit from java classes, and have java callback to ruby which calls
back to java, it can get messy.  Just try to keep it as simple as
possible.

Jason

[1]  http://arton.no-ip.info/collabo/backyard/?RubyJavaBridge
[2]  http://jruby.sourceforge.net