greg haygood

JRuby has been around for a little while, and is getting lots of attention for its ability to let Ruby developers code for a Java environment, and vice versa. However, as with many young projects, there isn't much documentation when it comes to the fringe cases.

The need I came across is the following: I have a client that's been running a JSP/servlet app under Tomcat for many years (originally started with JSP 0.91!). Over time I've added more and more functionality using the same JSP, Struts, etc. toolkits as everyone else uses. First up was a simple feature that involved sending some email notifications. It took me over an hour just to update the Strut-ified models (would've been even longer had I not used some Eclipse helpers), and another couple hours to add the business logic.

Just two weeks ago, I added this same functionality to a Rails app in about 30 minutes total (which included getting up to speed on ActionMailer)!

The client also needs a major piece of functionality added, which makes me shudder to think about having to code in Java. So I started looking into JRuby, and how it could let me add these features via Rails without changing the existing codebase. There's an add-on piece of code via goldspike/rails-integration that will let you package a rails app into a WAR file for deployment to any Java container. However, this (and all related posts and documentation) seems to assume you're just packaging a Rails-only app. I wanted to blend some new Rails functionality into my existing WAR. It took a few hours to work my way through the code, but finally came up with the following solution.

First, the Java web.xml needs the following stanzas added (make sure they get added in the correct order per the Servlet DTD):

<code>
&lt;context-param&gt;
	&lt;param-name&gt;rails.env&lt;/param-name&gt;
	&lt;param-value&gt;development&lt;/param-value&gt;
&lt;/context-param&gt;  &lt;servlet&gt;
	&lt;servlet-name&gt;rails&lt;/servlet-name&gt;
	&lt;servlet-class&gt;org.jruby.webapp.RailsServlet&lt;/servlet-class&gt;
	&lt;init-param&gt;
		&lt;param-name&gt;rails.root&lt;/param-name&gt;
		&lt;param-value&gt;/web/tomcat/webapps/jspapp/railsapp&lt;/param-value&gt;
	&lt;/init-param&gt;
&lt;/servlet&gt;
</code>

Next, the following line needs to be added to the environment.rb in your rails app:

<code>
ActionController::AbstractRequest.relative_url_root = "/jspapp/railsapp"
</code>

And then finally, to make sure the rails app code (outside of public) is not exposed, (assuming you're using Apache) add the following security controls to your front-end server:

<code>
&lt;Directory &quot;/web/tomcat/webapps/jspapp/railsapp&quot;&gt;
Order deny, allow
Deny from all
&lt;/Directory&gt;
&lt;Directory &quot;/web/tomcat/webapps/jspapp/railsapp/public&quot;&gt;
Order allow, deny
Allow from all
&lt;/Directory&gt;
</code>

Now you've got a blended webapp that lets you use Java or Rails in a seamless fashion!