Bye Merb Welcome Rack

saoj — GMT

The answer to my prayers has just arrived. It looks like a miracle, but it is actually a [i]Rack[/i] (not a hack).

Welcome to [url="http://rack.rubyforge.org/"]Rack[/url], a foundation framework that makes it easy to write your own web frameworks in Ruby. You can think of it as a Java Servlet API, at least the basic request and response paradigm.

Rack comes with [i]handlers[/i] for the most common Ruby web servers, such as [url="http://mongrel.rubyforge.org/"]Mongrel[/url] and WEBrick. For sanity reasons we will stick to Mongrel.

So I have given up Merb and welcome Mongrel + Rack + [url="http://www.kuwata-lab.com/erubis/"]Erubis[/url]. Erubis is a fast template engine for Ruby that we are going to use for our HTML page generators. You can think of Erubis as a Ruby Server Pages implementation, much like JSP.

Aside from the Mentawai web framework implementation, I wanted a web container as similar to Tomcat as possible when it comes to functionality. Therefore I implemented the following features not currently (as of 0.3.0) supported by Rack:

:arrow: Support for different applications (web contexts) running in the same server instance
:arrow: Support for session expiration and invalidation in a thread-safe way
:arrow: Support for added_to_session and removed_from_session callbacks (pretty much like [url="http://java.sun.com/products/servlet/2.2/javadoc/javax/servlet/http/HttpSessionBindingListener.html"]HttpSessionBindingListener[/url])
:arrow: Support for custom tags, but since we are using Erubis, a better name is: [i]custom page methods[/i] (more on that later)

Another great thing of Ruby is RubyGems. It can take some days to hack all the pieces together to make your gem available to the world, but thanks to [url="http://newgem.rubyforge.org/"]newgem[/url] this process can now take some hours instead of days. :-)

So ramp up your shell console and type:
[code]
C:\>gem -v
1.0.1
[/code]
You should see 1.0.1 as above. If you don't, just type:
[code]
c:\>gem update --system
[/code]
Wait until your RubyGems is updated to the latest version.

Then you need to install Mongrel, Rack, Erubis and Mentawai, in any order.
[code]
c:\>gem install mongrel
...
c:\>gem install rack
...
c:\>gem install erubis
...
c:\>gem install mentawai
...
[/code]
That's it. You are ready to play with all these precious [i]gems[/i]. Type [i]menta [/i]to make sure Mentawai was installed correctly:
[code]
C:\>menta
mentawai 0.5.0 - The Mentawai Web Framework implemented in Ruby
More information on http://www.mentaframework.org

-v,--version Show version
-h,--help Show this help
Create blank menta app
[/code]
Now all you have to do is go to a directory such as c:\my_ruby_projects and type [i]menta [/i] to create your blank Mentawai application:
[code]
C:\my_ruby_projects>menta HelloMenta
Create menta app "HelloMenta"
To run: ruby start.rb inside "HelloMenta"
[/code]
Success! Go to the [i]HelloMenta [/i]directory and check the files.
[code]
C:\my_ruby_projects\HelloMenta>dir
Volume in drive C has no label.
Volume Serial Number is 94CE-46A6

Directory of C:\my_ruby_projects\HelloMenta

03/17/2008 06:31 PM .
03/17/2008 06:31 PM ..
03/17/2008 06:31 PM actions
03/17/2008 06:31 PM 242 app_manager.rb
03/17/2008 06:31 PM 476 start.rb
03/17/2008 06:31 PM views
2 File(s) 718 bytes
4 Dir(s) 36,571,320,320 bytes free
[/code]
:arrow: The [i]start.rb[/i] file is what you will use to start the web server to serve your application.
:arrow: The [i]app_manager.rb[/i] is the old and famous Mentawai application manager.
:arrow: The [i]/actions[/i] directory is where you will place your actions
:arrow: The [i]/views[/i] directory is where you will place your pages (erubis templates)

Before we go into more details about these files, let's run our application so we can be happy:
[code]
c:\my_ruby_projects\HelloMenta\ruby start.rb
Loading app manager: app_manager.rb
Initializing application manager...
File mask: ./actions/**/*.rb
Loading ./actions/hello.rb
[/code]
Now point your browser to http://localhost:8081/Hello.mtw?username=Jack and you should see the results of your action.

[u]The start.rb file:[/u]
[code]
require 'rubygems'
require 'mentawai'

server = Mentawai::Server.new
server.host = '0.0.0.0'
server.port = 8080

# Setup the ROOT context (ROOT web application)
server.application('/', 'app_manager.rb', 'AppManager')

# You can setup as many applications as you want
# Ex:
# server.application('/myapp1', 'myapp1.rb', 'AppManager')
# server.application('/myapp2', 'myapp2.rb', 'AppManager')

# Start mongrel web server to server you mentawai app
server.start
[/code]
The comments say it all. You can create as many web applications and each one will have its own context path. For each application you specify a context path, the application manager file and the application manager class name. Then you start the server.

[u]The app_manager.rb file:[/u]
[code]
include Mentawai::Core

class AppManager < ApplicationManager

def init(appContext)
action("Hello").on(:success => Forward.new("hello.erb"))
addPageMethod(:m_my_method, 'Mentawai::Page::Method::Out', 'print')
end

end
[/code]
That's the good and old application manager. Mentawai has conventions for everything as well. Note how you can define your own page methods. (more about page methods in a later article!)

[u]The hello.rb action file:[/u]
[code]

class Hello < Mentawai::Core::Action

def execute

puts "Inside action Hello!"

username = input['username']

username = "NO USER" if username.nil?

output['username'] = username.upcase

:success

end
end
[/code]
[u]The hello.erb view page:[/u]
[code]

Hello1: <%= m_out('username') %>

Hello2: <%= m_my_method('username') %>

[/code]
That's it for now. After we have a solid foundation for the Mentawai architecture, we can start coding all the thousands features of the Mentawai framework. Thanks to Rack it looks like we are in the right track!

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Bye Merb Welcome Rack

Hello1: <%= m_out('username') %>

Hello2: <%= m_my_method('username') %>