web stacks

01-chain-of-responsibility.java

> Gives more than one object an opportunity 
> to handle a request by linking receiving objects together.


//Handler
public interface EmailHandler
{
	//reference to the next handler in the chain
	public void setNext(EmailHandler handler);
		
	//handle request
	public void handleRequest(Email email);
}

public class BusinessMailHandler implements EmailHandler
{
	private EmailHandler next;

	public void setNext(EmailHandler handler)
	{
	    next = handler;
	}
	
	public void handleRequest(Email email)
    {
		if(!email.getFrom().endsWith("@businessaddress.com")
		{
		    next.handleRequest(email);
		}
		else
		{
		    //handle request (move to correct folder)
		}

	}	

}

02-wsgi.py

def hello(environ, start_response):
    start_response('200 OK', [('Content-type','text/plain')])
    return ["Hello World!"]

# The Web Server Gateway Interface is a Python standard created in 2003 by Philip J. Eby
class Middleware(object):
    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        return self.app(environ, start_response)

app = Middleware(hello)

from wsgiref import simple_server

httpd = simple_server.WSGIServer(
    ('0.0.0.0', 8000),
    simple_server.WSGIRequestHandler,
)
httpd.set_app(app)
httpd.serve_forever()

03-rack.rb

require 'rack'
 
app = Proc.new do |env|
    ['200', {'Content-Type' => 'text/html'}, ['A barebones rack app.']]
end

class Middleware
  def initialize(app)
    @app = app       
  end                

  def call(env)
    # transform request
    new_env = cond? ? transform(env) : env
    # intercept
    return [status, headers, res] if cond?
    
    # transform responce 
    status, headers, response = @app.call(new_env)
    new_responce cond? ? transform(response) : response
    [status, headers, new_response]   
  end                
end              

use Middleware
Rack::Handler::WEBrick.run app

04-node-connect.js

var connect = require('connect')
var http = require('http')

var app = connect()

// gzip/deflate outgoing responses
var compression = require('compression')
app.use(compression())

// list of banned IPs
var banned = [
'127.0.0.1',
'192.168.2.12'
];

// the middleware function
blacklist = function() {
    
    return function(req, res, next) {
        if (banned.indexOf(req.connection.remoteAddress) > -1) {
            res.end('Banned');
        }
        else { next(); }
    }
    
};
app.use(blacklist());

// respond to all requests
app.use(function(req, res){
  res.end('Hello from Connect!\n');
})

//create node.js http server and listen on port
http.createServer(app).listen(3000)

05-ring.clj

(defn handler [req]
  {:status 200
   :headers {"Content-Type" "text/html"}
   :body "Hello World"})

(defn middleware [h & opt]
  (fn [req]
     (let [res (h req)]
        (transform res)))

(def app (-> handler middleware mw2 mw3))

(use 'ring.adapter.jetty)
(use 'hello-world.core)
(run-jetty app {:port 3000})

standard-middlewares.md

Standard Middlewares

• params
• multipart
• static files
• assets pipline
• session
• flash
• content type

https://github.com/ring-clojure/ring/tree/master/ring-core/src/ring/middleware

Advanced Patterns

https://github.com/ring-clojure/ring/wiki/Middleware-Patterns

• json request
• REST methods