After much poking and prodding it looks like Sinatra won’t work on top of JRuby Rack. It’s an unintended consequence of how everything was implemented, and it looks like some (hopefully minor) changes will have to be made to Sinatra.

Steps to get to where I am:

1. Install JRuby 1.1.2
2. Get tomcat - I used a 6.0.14 install I had laying around
3. Install the JRuby gem “warble”, which will come with jruby-rack
4. Create a new directory structure, described below
5. Copy jruby-complete.jar, and jruby-rack.jar to the WEB-INF/lib directory
6. Create a simple Sinatra hello world app
7. Create your web.xml file as described

The directory structure

jruby-sinatra/
jruby-sinatra/WEB-INF
jruby-sinatra/WEB-INF/web.xml
jruby-sinatra/WEB-INF/hello_world.rb
jruby-sinatra/WEB-INF/sinatra   # full copy of sinatra goes here
jruby-sinatra/WEB-INF/lib
jruby-sinatra/WEB-INF/lib/jruby-complete-1.1.1.jar
jruby-sinatra/WEB-INF/lib/jruby-rack-0.9.jar

My (non-working) current web.xml file.

<!DOCTYPE web-app PUBLIC
  "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
  "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
 
  <context-param>
    <param-name>public.root</param-name>
    <param-value>/</param-value>
  </context-param>
 
  <context-param>
    <param-name>rackup</param-name>
    <param-value>
        $:.unshift '/Users/cschneid/servers/apache-tomcat-6.0.14/webapps/jruby-sinatra/WEB-INF/'
        $:.unshift '/Users/cschneid/servers/apache-tomcat-6.0.14/webapps/jruby-sinatra/WEB-INF/sinatra/lib'
 
        puts "====================="
        puts "====================="
        puts "====================="
 
        puts "Current file is: #{__FILE__}"
        puts "Dollar 0 is: #{$0}"
 
        puts "List of load paths:"
        puts $:.map {|a| puts a }
 
        puts "====================="
        puts "====================="
        puts "====================="
 
        puts "Requiring sinatra"
        require "sinatra"
 
        puts "Setting up the sinatra app options"
        Sinatra::Application.default_options.merge!(
          :run => false,
          :env => :production
        )
 
        puts "About to require test"
        require 'test'
 
        puts "About to run sinatra"
        run Sinatra.application
    </param-value>
  </context-param>
 
 
  <filter>
    <filter-name>RackFilter</filter-name>
    <filter-class>org.jruby.rack.RackFilter</filter-class>
  </filter>
 
  <filter-mapping>
    <filter-name>RackFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
 
  <listener>
    <listener-class>org.jruby.rack.RackServletContextListener</listener-class>
  </listener>
 
</web-app>

The problem - the load fails on the Sinatra::Application.default_options.merge line. The first time you access default_options, it generates the hash. Every subsequent time, it just hands back the already created instance. Since this is the first time, it attempts to create the default_options structure. It gets a “root” of the directory tree from $0. And then later combines it with ‘/views’ and ‘/public’. The problem lies in the fact that we have a ruby script embedded inside the web.xml file. It doesn’t have a reasonable $0 to even set, so it doesn’t. If you ask for __FILE__, it just reports back with “<script>”. End result: you get a simple “can’t convert nil into String” exception thrown.

Next Steps - I don’t know, I think we should probably wean Sinatra off of $0 if at all possible. Or at least figure out how to set it to something reasonable so that default_options doesn’t blow up. If anybody has any ideas on how to go about this, let me know, since this doesn’t have an obvious fix that I see. Mainly, I don’t want to break functionality elsewhere (for plain ruby).

This entry was posted on Monday, June 9th, 2008 at 10:22 pm and is filed under Programming, Ruby, Sinatra. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.