Warbler, A Little Birdie To Introduce Your Rails App To Java

Warbler, A Little Birdie To Introduce Your Rails App To Java

Posted by Nick Sieger
on 2007年9月4日

This week I was working on integrating the latest JRuby 1.0.1 and Goldspike 1.3 releases into our environment, when my frustration hit a fever pitch.

See, I had always thought that the .war packaging side of Goldspike was a little clunky and
un-ruby-like, but I didn’t see a clear path to fixing it. I had heard little complaints about it here
and there: the little configuration DSL didn’t give you enough control or wasn’t documented well
enough; the fact that it downloads libraries from the internet during assembly (convenient, but not
safe or reproducible for production deployments).

Also, in my own opinion it took the wrong approach to packaging Rails in a .war file. It puts the
Rails application directory structure into the root of the .war file where any web server or Java
application server might mistakenly serve up your code as static content. The Java .war file spec has
this special directory called WEB-INF expressly for the purpose of hiding that stuff away, so why
not use it?

And then, suddenly Goldspike was packaging up my entire Rails application directory, .svn directories
and everything. So I set out to fix this once and for all.

And so I present Warbler. A little bird who chirpily steps up to the task of assembling your
Rails application into a Java Web Archive (.war). Here, get it:

gem install warbler

And then, in the top directory of your Rails application,

warble

Those two steps are all it takes to make a .war file, including your application and recent versions
of JRuby and Goldspike, that’s deployable to your favorite Java application server.

There are a number of points about Warbler worth mentioning.

Does one thing, well

Warbler only packages, and doesn’t care about anything else, like how to dispatch servlet requests to
Rails. This will allow for more runtime servlet binding mechanisms to take advantage of Warbler in
the future.

Fast and lightweight

50% less code than the Goldspike packaging plugin, yet does the job quickly and efficiently.

Sane defaults

Warbler only packages code that you need to run the application, omitting database migrations and
tests. If your application is self-sufficient (no external dependencies), then the out-of-the-box
configuration will probably work for you. Public HTML/images/javascript/stylesheets go in the root of
the webapp, where Java webservers expect them to be.

Documented, flexible configuration

Need to customize your configuration? Run warble config and edit config/warble.rb. All the
options are there, commented and documented.

Need to change out the bundled JRuby/Goldspike versions? warble pluginize makes a copy of Warbler
in the vendor/plugins area of your application, allowing you to change the .jar files in the
vendor/plugins/warbler-0.9/lib directory. Warbler then makes his nest in your project’s list of
rake tasks (as rake -T | grep war shows)

rake war            # Create trunk.war
rake war:app        # Copy all application files into the .war
rake war:clean      # Clean up the .war file and the staging area
rake war:gems       # Unpack all gems into WEB-INF/gems
rake war:jar        # Run the jar command to create the .war
rake war:java_libs  # Copy all java libraries into the .war
rake war:public     # Copy all public HTML files to the root of the .war
rake war:webxml     # Generate a web.xml file for the webapp

Warbler even omits himself in the .war file produced when running in plugin mode, since you won’t
need him at runtime. It’s the little details that matter.

Give him a try and let me know if it makes your life deploying Rails applications to JRuby on Java appservers easier!