Introducing JRuby-Rack

Nick Sieger — Thu, 08 May 2008 17:31:00 +0000

Continuing in the spirit of Conference-Driven Development, I’m happy to announce the first public release of JRuby-Rack! You can use it to run Rails, Merb, or any Rack-compatible application inside a Java application server.

Also released today is Warbler 0.9.9, which has been updated to bundle JRuby-Rack.

In addition to providing as seamless a connection as possible between the servlet environment and Rack, JRuby-Rack (along with Warbler) is also bridging the gap between Ruby and Java web development. Some of the things it does are:

Makes the Java servlet context and servlet request available to Ruby through special variables in the Rack environment
Servlet request attributes from Java are passed through and available in the Rack environment. Request attributes can override Rack variables such as PATH_INFO, QUERY_STRING etc.
Configures Rails deployment options such as page caching directories and session handling automatically and optimally for the servlet environment.

I’ve also included the beginnings of some extensions that should help integrate Rails with existing Java web frameworks, servlets, JSPs, and other code. For example, you can invoke a Rails request from within a JSP with a tag:

<jruby-rack:rails path="/projects/activity" params="layout=none"/>

You can set servlet and session attributes and forward to other servlets and JSPs from your Rails controllers:

class DemoController < ApplicationController
  def index
    servlet_request["hello"] = "world!"
    session["rails"] = "Visible to java!"
    forward_to "/attributes.jsp"
  end
end

and read them from within the servlet or JSP:

<dl>
  <dt><tt>servlet_request["hello"] | request.getAttribute("hello")</tt></dt>
  <dd><%= request.getAttribute("hello") %></dd>
  <dt><tt>session["rails"] | session.getAttribute("rails")</tt></dt>
  <dd><%= session.getAttribute("rails") %></dd>
</dl>

This is just the beginning of this kind of integration, and I’m interested where people take it. I think this provides a nifty way to start integrating Rails bits into existing applications or reuse existing Java web application code.

I’ve tagged the release with an 0.9 version number. I believe the bits are ready for serious use, but could use some help pounding out a few more bugs before calling it 1.0. So jruby -S gem install warbler today, try it out, and bring plenty of feedback to the JRuby user list!

Nick Sieger: Tag merb

Introducing JRuby-Rack