You've found a really useful RubyGem but can't use it on your JRuby Windows machine because it's a native C extension. And yes, it's only available in source. And if you did get it to compile, you'd slam face first into the well-known fact that JRuby doesn't work with native RubyGems.
Fahrvergnügen!
"No problem, I'll just port it to Java" says your always-optimistic-but-clueless other self. "Great, another one-off to support" you mutter as reality saunters back into view.
Just about to call it quits, you find this post about some cool Ruby Summer of Code work by Tim Felgentreff. Oddly, you stumble upon the DevKit toolchain for Windows systems, it falls into place, and everything begins to look a little brighter.
But why would anyone do that? Well, one of the JRuby guys has a few words on the matter.
Always the sceptic realist, you decide to see how The Pipe Dream
works out with a few of the well-known native RubyGems from the ether.
Turns out, it's as easy as:
Using your existing msysgit installation, type
C:\>git clone git://github.com/jruby/jruby.git jruby-dev Cloning into jruby-dev... done. C:\>
First, download the DevKit and install it to a
directory without spaces, say C:\DevKit. Next, run the following after you've updated
the DevKit's config.yml file to point to the JRuby repository you just cloned. For
more detailed instructions check out the DevKit installation
and DevKit upgrade wiki pages.
C:\DevKit>type config.yml # ...SNIP... # --- - C:/jruby-dev C:\DevKit>ruby dk.rb install [INFO] Installing 'C:/jruby-dev/lib/ruby/site_ruby/1.8/rubygems/defaults/operating_system.rb' [INFO] Installing 'C:/jruby-dev/lib/ruby/site_ruby/shared/devkit.rb' C:\DevKit>
Make sure you've setup your Ant+JDK build environment correctly, bring the
DevKit's build tools and git onto PATH, and build JRuby via
C:\DevKit>devkitvars Adding the DevKit to PATH... C:\DevKit>cd \jruby-dev C:\jruby-dev>echo %PATH% C:\DevKit\bin;C:\DevKit\mingw\bin;C:\git\cmd;C:\ant\bin;C:\Program Files\Java\jdk1.6.0_22\bin; C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem C:\jruby-dev>ant clean jar cext ...SNIP... cext: BUILD SUCCESSFUL Total time: 2 minutes 5 seconds C:\jruby-dev>
Ensure your setup is correct by opening a new shell, adding your newly built
JRuby to PATH, and running a quick smoke test via
C:\>echo %PATH%
C:\jruby-dev\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem
C:\>jruby --version
jruby 1.6.0.dev (ruby 1.8.7 patchlevel 249) (2010-11-30 88ad204) (Java HotSpot(TM)
Client VM 1.6.0_22) [Windows 7-x86-java]
C:\>jruby -e "puts 'Hello from Ruby-on-%s' % RUBY_PLATFORM.capitalize"
Hello from Ruby-on-Java
C:\>jruby -S gem env
RubyGems Environment:
- RUBYGEMS VERSION: 1.3.7
- RUBY VERSION: 1.8.7 (2010-11-30 patchlevel 249) [java]
- INSTALLATION DIRECTORY: C:/jruby-dev/lib/ruby/gems/1.8
- RUBY EXECUTABLE: C:/jruby-dev/bin/jruby.exe
- EXECUTABLE DIRECTORY: C:/jruby-dev/bin
- RUBYGEMS PLATFORMS:
- ruby
- universal-java-1.6
- GEM PATHS:
- C:/jruby-dev/lib/ruby/gems/1.8
- C:/Users/Jon/.gem/jruby/1.8
...SNIP...
C:\>
Now, let's install the rdiscount and curb gems.
rdiscount is simple enough, but to install curb you need to have already
installed curl's header and library development artifacts. As the DevKit is
based upon MinGW, a great place to get these development artifacts
is from Guenter Knauf who distributes Curl's Windows binaries. Thank him when
you get a moment.
Although I use jruby -S gem you can also use just gem if the JRuby bindir
is the only (or first) Ruby on your PATH. Note, the --platform=ruby option
forces RubyGems to attempt to build the native gem rather than trying to install
a gem specifically built for JRuby. For example, EventMachine
has a Java specific gem in addition other platform specific gems and a source gem.
But that is a topic for a future post.
Moving on...
C:\>jruby -S gem install rdiscount --platform=ruby JRuby limited openssl loaded. http://jruby.org/openssl gem install jruby-openssl for full support. Temporarily enhancing PATH to include DevKit... Building native extensions. This could take a while... Successfully installed rdiscount-1.6.5 1 gem installed C:\>jruby -S gem install curb --platform=ruby -- --with-curl-lib="c:/curl/bin" --with-curl-include="c:/curl/include" JRuby limited openssl loaded. http://jruby.org/openssl gem install jruby-openssl for full support. Temporarily enhancing PATH to include DevKit... Building native extensions. This could take a while... Successfully installed curb-0.7.8 1 gem installed C:\>jruby -S gem list *** LOCAL GEMS *** curb (0.7.8) rdiscount (1.6.5) sources (0.0.1) C:\>
Make sure the directory you used with --with-curl-lib containing the curl DLL
is on PATH.
C:\>jruby -rubygems -e "require 'rdiscount'; puts RDiscount.new('**Hello JRuby**').to_html"
calling init (63288dd6)
<p><strong>Hello JRuby</strong></p>
C:\>type curbee.rb
require 'rubygems'
require 'curb'
c = Curl::Easy.perform("http://www.google.com")
puts 'URL: %s' % c.url
puts 'IP: %s' % c.primary_ip
puts 'Request Size: %s' % c.request_size
C:\>jruby curbee.rb
calling init (63fc1560)
URL: http://www.google.com
IP: 72.14.204.103
Request Size: 53
C:\>
Yeh!
So what does it all mean? Simply put, a wider spectrum of code reuse options for you as both a developer and user of JRuby on Windows.
One of the more interesting options is the ability to defer, perhaps completely, custom development by enabling you to focus your limited resources on the areas of your product in which you add real value, thereby getting you to 'go-live' faster. For me, JRuby's C extension support is a compelling code reuse and aggregation technology that enhances JRuby's existing integration capabilities.
From that perspective, take another read of both Tim and Charles posts.
Is it really always this easy? Well, most of the times yes, but sometimes no. There are a few caveats, but they're for a future post. For example, why is the first "failure" not really a failure?
C:\>jruby -S gem install eventmachine --platform=ruby --pre
JRuby limited openssl loaded. http://jruby.org/openssl
gem install jruby-openssl for full support.
Temporarily enhancing PATH to include DevKit...
Building native extensions. This could take a while...
ERROR: Error installing eventmachine:
ERROR: Failed to build gem native extension.
...SNIP...
cmain.cpp:752:20: error: 'fstat' was not declared in this scope
g++.exe: unrecognized option '-EHs'
g++.exe: unrecognized option '-GR'
make: *** [cmain.o] Error 1
C:\>jruby -s gem install eventmachine --pre
JRuby limited openssl loaded. http://jruby.org/openssl
gem install jruby-openssl for full support.
Successfully installed eventmachine-1.0.0.beta.2-java
1 gem installed
C:\>