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Restful Services in Ruby using JRuby and Jersey

by Dilip Krishnan on Jun 02, 2010 |

In an effort to bring the expressiveness of ruby and the REST frameworks in Java, Charles Nutter makes the case for delevoping RESTful services using JRuby+Rails. He observes the inherent thought leadership in the Ruby and Rails communities in building RESTful applications that leverage the web.

[…] Rubyists have been helping to lead the way, building restfulness into just about everything they write. Rails itself is built around REST, with most controllers doubling as RESTful interfaces, and it even provides extra tools to help you transparently make RESTful calls from your application. If you're doing RESTful services for a typical Ruby application, Rails is the way to go.

To demonstrate the ability to define a RESTful service in JRuby, he surveys the solution landscape for libraries and frameworks for building RESTful services in Java. He starts with a simple example service using the standard JAX-RS API 

I followed the Jersey Getting Started tutorial using Ruby for everything (and not using Maven in this case). My version of their HelloWorldResource looks like this in Ruby:

require 'java'java_import 'javax.ws.rs.Path'
java_import 'javax.ws.rs.GET'
java_import 'javax.ws.rs.Produces'

java_package 'com.headius.demo.jersey'
java_annotation 'Path("/helloworld")'
class HelloWorld
java_annotation 'GET'
java_annotation 'Produces("text/plain")'
def cliched_message
"Hello World"
end
end

He describes the internals of how the ruby class gets compiled and the internals of the in memory representation of the object.

Under the covers, this class will load in the source of our restful_service.rb file and wire up all the Ruby and Java pieces so that both sides see HelloWorld as the in-memory representation of the Ruby HelloWorld class. Method calls are dispatched to the Ruby code, constructors dispatch to initialize, and so on. It's truly living in both worlds.
With the service in hand, we now need a server script to start it up.

He proceeds to deal with the notoriously-hard-to-get-right CLASSPATH so that the example can run.

I've tossed them into my CLASSPATH env var, but you're free to do it however you like

jersey-core-1.2.jar
jersey-server-1.2.jar
jsr311-api-1.1.1.jar
asm-3.1.jar
grizzly-servlet-webserver-1.9.9.jar

The first four are available in the jersey-archive download, and you can fetch the Grizzly jar from Maven or other places.

He concludes with a call for “examples of other nice annotation-based APIs we could test out with JRuby?” Do share interesting examples in the forum and visit the original post for details on writing RESTful services in JRuby.

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