JRuby, Warbler, and Java's CLASSPATH

Question

I've been developing applications in JRuby lately and really enjoying it, but I've been running into a wall when it comes to packaging my project into a JAR file when it includes external Java libraries. If the project does not depend on any external Java library JAR files, I run into no problems.

Below is an example application. This code works perfectly fine when running the ./bin/my_proj executable. But, when I package it into a JAR file, the external Java library cannot be loaded because it is not found on the CLASSPATH.

When I unpackage my application's JAR file, I can see that it includes all of my code as well as the vendor directory containing the external Java library. So, everything's where it should be.

lib/my_proj/application.rb

java_import 'com.somecompany.somejavalibrary.SomeJavaLibraryClass'

module MyProj

  class Application < SomeJavaLibraryClass

    # Some code implementing SomeJavaLibraryClass

  end

end

lib/my_proj.rb

require 'pathname'

module MyProj

  def root
    Pathname.new(__FILE__).join('..', '..').expand_path
  end

  def start
    setup_environment

    Application.new
  end

  def setup_environment
    @setup ||= false

    unless @setup
      @setup = true

      require 'java'

      $CLASSPATH << root.join('vendor').to_s # Setup Java CLASSPATH
      $LOAD_PATH << root.join('lib').to_s    # Setup Ruby LOAD_PATH

      require 'some_java_library' # Load the external Java library from it's JAR

      require 'my_proj/application'
    end
  end

  extend self

end

bin/my_proj

#!/usr/bin/env ruby

$:.unshift File.expand_path( File.join('..', '..', 'lib'), __FILE__ )
require 'my_proj'

MyProj.start

config/warble.rb

Warbler::Config.new do |config|
  config.features = %w(gemjar compiled)
  config.autodeploy_dir = 'pkg'
  config.dirs = %w(assets bin config lib)
  config.java_libs += FileList['vendor/*.jar']
end

vendor/some_java_library.jar

# This is the external Java library

Answer 1

The external jars should be in the lib folder.

You can add them in code by doing something like

$CLASSPATH << "vendor/some_java_library.jar" #or loop the directory for all jars and add them

Or you can create a META-INF/MANIFEST.MF file and specifiy the CLASSPATH jars

and adding a line like

Class-Path: vendor/some_java_library.jar jar2-name directory-name/jar3-name

http://docs.oracle.com/javase/tutorial/deployment/jar/downman.html