måndag, oktober 02, 2006

The JRuby Tutorial #3: Playing with Mongrel

This part of the tutorial will be based on some slightly not-released software, but since it is so cool, I bet you will try it anyway. Basically, what I'm going to show you is how to get Mongrel 0.4 working with JRuby, and then how you can serve your JRuby on Rails-application with said version of Mongrel.

What you'll need
First of all, check out the latest trunk version of JRuby. There are some smoking new fixes in there that is needed for this hack. Next, you will also need to check out the 0.4-branch of Mongrel. This can be done with the following command:
svn co svn://rubyforge.org/var/svn/mongrel/branches/mongrel-0.4
You need to manually copy two parts of mongrel into your JRuby home. If $MONGREL_SRC is the name of the directory where you checked out mongrel, these commands will suffice:
cp -r $MONGREL_SRC/lib/mongrel* $JRUBY_HOME/lib/ruby/site_ruby/1.8
cp $MONGREL_SRC/projects/gem_plugin/lib/gem_plugin.rb $JRUBY_HOME/lib/ruby/site_ruby/1.8
echo '#\!/usr/bin/env jruby' > $JRUBY_HOME/bin/mongrel_rails
cat $MONGREL_SRC/bin/mongrel_rails >> $JRUBY_HOME/bin/mongrel_rails
chmod +x $JRUBY_HOME/bin/mongrel_rails
You will need to download the JRuby-specific http11-extension library. This can be downloaded here, and should also be put in the $JRUBY_HOME/lib/ruby/site_ruby/1.8-directory.

You're now set to go.

Simple web hosting
I will now show how to set up at small web server, that can serve both files and servlets. There really isn't much to it. First of all, we need to include some libraries:
require 'mongrel'
require 'zlib'
require 'java'
include_class 'java.lang.System'
Next step is to create a simple HttpHandler (which is like a Servlet, for you Java-buffs):
class SimpleHandler < Mongrel::HttpHandler
def process(request, response)
response.start do |head,out|
head["Content-Type"] = "text/html"
results = <<-"EDN";
Your request:
<a href=\"/files\">View the files.</a><br/>

if request.params["HTTP_ACCEPT_ENCODING"] == "gzip,deflate"
head["Content-Encoding"] = "deflate"
# send it back deflated
out << Zlib::Deflate.deflate(results)
# no gzip supported, send it back normal
out << results
Now, this handler basically just generates a bunch of HTML and sends it back. The HTML contains the request parameters. Just to show how easy it is to combine Java-output with Ruby-output, I have added a call to System.currentTimeMillis. This could of course by anything. The last part is to actually make this handler active also. To finalize, we also start the server:
@simple = SimpleHandler.new
@http_server = Mongrel::HttpServer.new('',3333)
@http_server.register("/", @simple)
if ARGV[0]
@files = Mongrel::DirHandler.new(ARGV[0])
@http_server.register("/files", @files)

puts "running at"

If you start this script with:
jruby testMongrel.rb htdocs
you can visit localhost:3333 and expect to see some nice output.

Making it work with Rails
A prerequisite for this part is that you have a functional JRuby on Rails-application using ActiveRecord-JDBC. If that is the case, you just need to go your application directory and execute this command:
$JRUBY_HOME/bin/mongrel_rails --prefix "" start
and everything should just work.

So, that's it. JRuby on Rails, with Mongrel. Enjoy.

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