Using Rubygems to Package Java Jarfiles

Ruby
1

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

2

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 B. (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.

3

Ola B. 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