Ruby Forum Ruby > Using Rubygems to Package Java Jarfiles

Ruby Java Bridge (RJB) (http://rjb.rubyforge.org/) a good way to use 
Java classes and maintain the abiltity to work with both C extensions 
and develop Rails applications.

If you could package Java jarfiles in a Rubygem, that would be the 
ultimate in convenience. A user could simply use the "gem install" 
command, which would automatically install RJB if needed, the jarfile, 
and any necessary Ruby glue code. The user could then have access to the 
Java library.

The whole process would be essentially the same as working with any 
other Rubygem. Any library that depends on this java-ruby hybrid can use 
it like any other Rubygem, with all of the advantages.

I've already built a Gem that installs a jarfile. Here's the problem: 
with RJB, the jarfiles you use can be specified with:

ENV['CLASSPATH'] = 'my_jarfile.jar'

My question is: how do I locate my_jarfile.jar?

One possibility seems to be Gem.dir, which gives the top-level directory 
for installed Gems.

But I need to get the path to my Gem's directory. One way I came up with 
was to use (assuming I've got foo-0.1.0):

gem_path = Gem.dir + '/gems/foo-0.1.0/'
ENV['CLASSPATH'] = gem_path + 'my_jarfile.jar'

I've used this approach and it works. But it seems like there must be a 
more elegant way to get to a particluar Gem's installation directory. 
Also, is there a better way to do what I'm trying to do?

thanks,
Rich

Rich Apodaca wrote:
> The whole process would be essentially the same as working with any 
> One possibility seems to be Gem.dir, which gives the top-level directory 
> Also, is there a better way to do what I'm trying to do?
> 
> thanks,
> Rich
> 

Hi Rich,

We're working on an approach like this for packaging Java extensions to
Ruby systems. If we get what we want, you'll be able to (from JRuby) do
gem install mongrel, choose java-version (instead of linux or mswin32)
from the list, and the Java extension will be automatically installed.
This requires the JRuby runtime to work, of course.

--
  Ola Bini (http://ola-bini.blogspot.com)
  JvYAML, RbYAML, JRuby and Jatha contributor
  System Developer, Karolinska Institutet (http://www.ki.se)
  OLogix Consulting (http://www.ologix.com)

  "Yields falsehood when quined" yields falsehood when quined.

Ola Bini wrote:
> Rich Apodaca wrote:
>> The whole process would be essentially the same as working with any 
>> One possibility seems to be Gem.dir, which gives the top-level directory 
>> Also, is there a better way to do what I'm trying to do?
>> 
>> thanks,
>> Rich
>> 
> 
> Hi Rich,
> 
> We're working on an approach like this for packaging Java extensions to
> Ruby systems. If we get what we want, you'll be able to (from JRuby) do
> gem install mongrel, choose java-version (instead of linux or mswin32)
> from the list, and the Java extension will be automatically installed.
> This requires the JRuby runtime to work, of course.

Thanks for the info, Ola. I've written an article describing another 
solution that works with the C Ruby implementation (letting you use C 
extensions _and_ Java at the same time):

http://depth-first.com/articles/2006/09/14/cdk-the-ruby-way

It might also work with JRuby.

Best,
Rich