Ice Breakers

Factories, Factories, Factories

Java Enterprise Architecture

Why Ruby?

Keep it Simple - Web Apps Case Study

  1. No Enterprise Java Application Server
    • Use Embedded Jetty Library to Run Container-Less
  2. No Enterprise Java Database Server
    • Use Embedded SQLite Library
  3. No Enterprise Java Application Framework
    • Use Embedded Ruby Library
  4. No Enterprise Java IDE
    • Use Command Line, Programmer’s Editor

Case Study: How to Install Container-Less Jetty Web Server

Step 1: Copy jetty-webapp-7.x.jar (~ 1 Meg)

Step 2: There is no step 2.

Think Different - What’s Container-Less?

Container-Less? Run your web application as a plain old Java process.

Why:

A Simple Web App using Jetty

The simplest possible Jetty server:

import org.eclipse.jetty.server.Server;
    
public class SimpleServer
{
  public static void main(String[] args) throws Exception
  {
    Server server = new Server(8080);
    server.start();
    server.join();
  }
}

A Simple Web App using Jetty (Cont.)

import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.webapp.WebAppContext;

public class AppServer
{

  public static void main(String[] args) throws Exception
  {
    Server server = new Server(8080);
 
    WebAppContext webapp = new WebAppContext();
    webapp.setContextPath("/");
    webapp.setWar( "./links.war");
    server.setHandler(webapp);
 
    server.start();
    server.join();
  }
}

Compile

javac -cp .;./jetty-webapp-7.x.jar AppServer.java

Let’s Build a Link Bookmarking and Voting Web App

Create a Web App using Ruby on Rails

Create Web App Structure

$ rails links

Create SQLite Schema (db/migrate/create_db.rb)

create_table :links do |t|
  t.string  :title,  :null => false 
  t.string  :url,    :null => false
  t.integer :points, :default => 0
  t.timestamps   # note: macro adds created_at, updated_at
end

Create SQLite DB

$ rake db:setup     # note: rake is ruby make (simple build tool)

Model / View / Controller (MVC)

Model (models/link.rb)

class Link < ActiveRecord::Base

  # self.table_name = 'links'
 
  attr_accessor :score 

  def recalc_score
    time_elapsed = (Time.now - self.created_at) / 36000  # in hours
    self.score = ((self.points-1) / (time_elapsed+2)**1.8)
  end
 
  def self.hot
    self.all.each { |rec| rec.recalc_score }.sort { |l,r| l.score <=> r.score }.reverse
  end
  
end

Model / View / Controller (MVC)

Controller (controllers/links_controller.rb)

class LinksController < ApplicationController
  
  # GET /
  def index    
    @links = Link.order( 'created_at desc' ).all
  end

  # GET /hot
  def hot
    @links = Link.hot
    render :index
  end

  # POST /
  def create
    l = Link.new( params[:link] )
    l.save!
    redirect_to :back    
  end

  # PUT /:id/vote/:type
  def vote
    l = Link.find( params[:id] )
    l.points += params[:type].to_i
    l.save!
    redirect_to :back    
  end
  
end

Model / View / Controller (MVC)

View (views/links/index.html.erb)

<table id='links'>
<% @links.each do |l| %>

<tr>
  <td class='points'>
    <%= form_for l, :url => vote_link_path( l, :type => '1' ), :method => 'PUT' do |f| %>
      <%= f.submit '+1' %>
    <% end %>
      
    <%= l.points %>

    <%= form_for l, :url => vote_link_path( l, :type => '-1' ), :method => 'PUT' do |f| %>
      <%= f.submit '-1' %>
    <% end %>            
  </td>
  <td><span class='title'><%= link_to l.title, l.url %></span>
      <span class='host'>(<%= l.url_host %>)</span>
      <span class='created-at'>posted <%= time_ago_in_words(l.created_at) %> ago</span>
  </td>
</tr>
  
<% end %>
</table>

<div id='post-link'>

  <%= form_for :link, :url => links_path() do |f| %>
    <%= f.text_field :title, :placeholder => 'Title' %>
    <%= f.text_field :url,   :placeholder => 'URL' %>
    <%= f.submit 'Save Link' %>
  <% end %>
  
</div>

Zip Up and Run It

Zip Up as Java Web Archive (links.war)

$ rake war      # warble

Run it

$ java -cp .;./jetty-webapp-7.x.jar AppServer

Surprise ??

=> One Plain Old Java Process - Embedded Jetty, Embedded SQLite, Embedded Ruby

Case Study: How to Install Embedded Ruby

Step 1: Copy jruby-complete-1.7.x.jar

Step 2: There is no step 2.

Java Web Archive (.war) Directory Structure

links.war

|_ images
|  | _<empty>
|_ stylesheets
|  |_ application.css
|_ javascripts
|  | _<empty>
|_ WEB-INF
   |_ app
   |  |_ controllers
   |  |  |_ links_controller.rb
   |  |_ models
   |  |  |_ link.rb
   |  |_ views
   |     |_ layouts
   |     |  |_ application.html.erb
   |     |_ links
   |        |_ index.html.erb
   |_ config
   |  |_ database.yml
   |  |_ routes.rb
   |_ db
   |  |_ links.sqlite3
   |_ lib
      |_ jruby-complete-1.7.x.jar
      |_ jruby-rack-1.x.jar
      |_ gems.jar

What’s missing in Java? What’s wrong with Java?

Anyone?

Simple Data Structures (Maps, Arrays)

Example:

{ customer:
  { id: '12345',
    first_name: 'Carlos',
    last_name:  'Lafata',
    address:
    [
      { typ:      'home',
        line1:    'Burgring 11',
        city:     'Wien',
        zip_code: '1010' },
      { typ:      'work',
        line1:    'Nestroyplatz 12',
        city:     'Wien',
        zip_code: '1020' }
    ] }
}

Quiz: Built into what modern languages?

[ X ] JavaScript

[ X ] Ruby

[ X ] Scala

[ ] ~~Java~~

[ ] ~~COBOL~~

Simple Code Blocks (Higher Order Functions, Functions as First Class Types)

Example:

// Assign Function to Variable

var greet =  function() {  document.write( 'Welcome. Benvenuti. Willkommen.' ); }

// Call Function Stored in Variable

greet();

// Function as Function Parameter

function say( what )
{
  what();
  what();
  what();
}

// Pass Function Stored in Variable to Function

say( greet );

Quiz: Built into what modern languages?

[ X ] JavaScript

[ X ] Ruby

[ X ] Scala

[ ] ~~Java~~

[ ] ~~COBOL~~

Part II

Building Web Services (HTTP APIs) with Ruby (and Sinatra)

Agenda

What’s Sinatra?

Simple (yet powerful and flexible) micro webframework.

require 'sinatra'

get '/' do
  'Hallo Wien!'
end

Sinatra itself less than 2000 lines of code.

Installation. Type in your terminal (shell):

$ gem install sinatra

What’s Sinatra? (Continued)

Example - hallo.rb:

require 'sinatra'

get '/' do
  'Hallo Wien!'
end

Run script (server):

$ ruby hallo.rb

>> Sinatra has taken the stage...
>> Listening on 0.0.0.0:4567, CTRL+C to stop

Open browser:

Let a Thousand Sinatra Clones Bloom

Micro Frameworks Inspired by Sinatra

Express.js (in Server-Side JavaScript w/ Node.js):

var express = require( 'express' );
var app = express();

app.get( '/', function( req, res ) {
  res.send( 'Hallo Wien!' );
});

app.listen( 4567 );

Scotty (in Haskell):

import Web.Scotty

main :: IO ()
main = scotty 4567 $ do
    get "/" $ text "Hallo Wien!"

Dancer (Perl), Fitzgerald (PHP), Ratpack (Groovy), Zappa (CoffeeScript), Mercury (Lua), Frank (F#), Nancy (C#/.NET), Bogart (C), Flask (Python), and many more.

Why Sinatra? Goodies

1) Single file scripts

2) Easy to package up into a gem. Example:

$ gem install beerdb     # Yes, the beerdb includes a Sinatra app.

3) Lets you build command line tools. Example:

$ beerdb serve           # Startup web service (HTTP API).

4) Lets you mount app inside app (including Rails). Example:

mount BeerDb::Server, :at => '/api/v1'

Example Web Service (HTTP API) - Routes

Lets build a beer and brewery API.

Get beer by key /beer/:key. Examples:

Get brewery by key /brewery/:key. Examples:

Bonus:

Get random beer /beer/rand and random brewery /brewery/rand.

Sinatra in Action - get '/beer/:key'

beerdb/server.rb:

get '/beer/:key' do |key|

  beer = Beer.find_by_key!( key )
  json_or_jsonp( beer.as_json )

end

get '/brewery/:key' do |key|

  brewery = Brewery.find_by_key!( key )
  json_or_jsonp( brewery.as_json )

end

That’s it.

Bonus:

get '/beer/:key' do |key|

  if ['r', 'rnd', 'rand', 'random'].include?( key )
    beer = Beer.rnd.first
  else
    beer = Beer.find_by_key!( key )
  end

  json_or_jsonp( beer.as_json )
end

get '/brewery/:key' do |key|

  if ['r', 'rnd', 'rand', 'random'].include?( key )
    brewery = Brewery.rnd.first
  else
    brewery = Brewery.find_by_key!( key )
  end

  json_or_jsonp( brewery.as_json )
end

What’s JSON?

JSON = JavaScript Object Notation

Example - GET /beer/ottakringerhelles:

{
  key: "ottakringerhelles",
  title: "Ottakringer Helles",
  synonyms: "16er Blech|16er Hüs'n",
  abv: "5.2",
  og: "11.8",
  tags: [ "lager" ],
  brewery: {
    key: "ottakringer",
    title: "Ottakringer Brauerei"
  },
  country: {
   key: "at",
   title: "Austria"
  }
}

What’s JSONP?

JSONP = JSON with Padding. Why?

Call Home Restriction. Cross-Domain Browser Requests Get Blocked.

Hack: Wrap JSON into a JavaScript function/callback e.g. functionCallback( <json_data_here> ) and serve as plain old JavaScript.

Example - Content-Type: application/json:

{
  key: "ottakringerhelles",
  title: "Ottakringer Helles",
  synonyms: "16er Blech|16er Hüs'n",
  abv: "5.2",
  ...
}

becomes Content-Type: application/javascript:

functionCallback(
  {
    key: "ottakringerhelles",
    title: "Ottakringer Helles",
    synonyms: "16er Blech|16er Hüs'n",
    abv: "5.2",
    ...
  }
);

Bonus: Little Sinatra helper for JSON or JSONP response (depending on callback parameter).

def json_or_jsonp( json )
  callback = params.delete('callback')

  if callback
    content_type :js
    response = "#{callback}(#{json})"
  else
    content_type :json
    response = json
  end
end

Serializers - From Ruby Objects (in Memory) to JavaScript Object (in Text)

JSON built into Ruby 2.0 as a standard library. Example:

require 'json'

hash =
{
  key:   "ottakringerhelles",
  title: "Ottakringer Helles"
}

1) JSON.generate

puts JSON.generate( hash )

>> {"key":"ottakringerhelles","title":"Ottakringer Helles"}

2) #to_json

puts hash.to_json

>>  {"key":"ottakringerhelles","title":"Ottakringer Helles"}

Serializers - From Ruby Objects (in Memory) to JavaScript Object (in Text) Continued

Serializers for your Models. Example:

class BeerSerializer

  def initialize( beer )
    @beer = beer
  end

  attr_reader :beer

  def as_json
    data = { key:      beer.key,
             title:    beer.title,
             synonyms: beer.synonyms,
             abv:      beer.abv,
             ...
           }
    data.to_json
  end

end # class BeerSerializer

And add as_json to your Model. Example:

class Beer < ActiveRecord::Base

  def as_json_v2( opts={} )
    BeerSerializer.new( self ).as_json
  end

end # class Beer

Appendix: What’s Rack?

Lets you mix ‘n’ match servers and apps.

Lets you stack apps inside apps inside apps inside apps inside apps.

Good News: A Sinatra app is a Rack app.

Learn more about Rack @ rack.github.io.

Appendix: Sinatra Books

Sinatra: Up and Running by Alan Harris, Konstantin Haase; November 2011, O’Reilly, 122 Pages

Jump Start Sinatra by Darren Jones; January 2013, SitePoint, 150 Pages

What’s vienna.rb? Ruby User Group Vienna

Next meetup: Fri, October 11th @ Sektor5

Talks (*)

Jakob Sommerhuber - sponsor talk

Martin Schürrer - Erlang/OTP in production for highly-available, scalable systems

Markus Prinz - How to improve your code

Gerald Bauer - working with Sinatra

Kathrin Folkendt - ‘Chapter one’ (lightning talk on getting started with Rails, and building her first web app)

(*) preliminary program

That’s it. Thanks.

1) Don’t put yourself in the Java ghetto (or Java rules the world hybris)

=> Learn new concepts or languages

2) Web architecture is more than Java enterprise architecture

=> Learn HTML, JS, CSS, HTTP (REST), SQL/NoSQL, etc.

Questions? Comments?