This document provides an overview of Ruby for Java developers, covering the history and culture of both languages, their technical backgrounds, key differences in their languages and frameworks, and how Ruby on Rails works. It demonstrates Ruby concepts through examples and concludes with a discussion on performance and common use cases for each language.

1. Ruby for Java
Developers
!
Robert Reiz

2. Robert Reiz
http:/
/robert-reiz.com
https:/
/twitter.com/robertreiz
!
http:/
/about.me/robertreiz
!
http:/
/www.VersionEye.com

3. Agenda
History
Java/Ruby Culture Background
Java/Ruby Tech. Background
Ruby Lang
Rails - Short Intro + Tools
Rails Demo App
Performance
Else
The End

4. A Presentation is no
Documentation
A good presentation supports only the speaker

5. History
Yukihiro Matsumoto in Japan
1993 first ideas
1995 Version 0.95 released

6. History
"I wanted a scripting language that was more
powerful than Perl, and more object-oriented
than Python. That's why I decided to design my
own language."
- Matsumoto

7. History
"Often people, especially computer engineers, focus on
the machines. They think, "By doing this, the machine
will run faster. By doing this, the machine will run more
effectively. By doing this, the machine will something
something something." They are focusing on machines.
But in fact we need to focus on humans, on how humans
care about doing programming or operating the
application of the machines. We are the masters. They
are the slaves."
- Matsumoto

8. History
for (int i = 0 ; i < 3 ; i++){
System.out.println(“Hallo World”);
}
3.times{
print “Hallo World”
}

9. History
Language developed by Open Standards
Promotion Center of the InformationTechnology Promotion Agency
2011: Japanese Industrial Standard (JIS X
3017)
2012: International standard (ISO/IEC 30170)

10. Culture Background
“Java Programmers are writing strange
Ruby Code.”

11. Java Culture
JME
Java for Desktops
(Swing, AWT,
JavaFX)
J EE

12. Java Culture = Enterprise Culture
Enterprise Environment

13. Java Culture
Waterfall
Servlet
LDAP
Intranet
Eclipse
Excel
Application Server
Oracle
Jira
Deadlines
Outlook
Requirements
SVN
SLAs
EJB

14. Ruby Culture
Start-Up Culture in Silicon Valley

15. Ruby Culture
Start-Up Environment (Epicenter Cafe @ SF)

16. Ruby Culture
Start-Up Environment (The Summit @ SF)

17. Ruby Culture
Hackathon

18. Fail fast
Fail early

19. Ruby Culture
Login with Twitter / Facebook
OAuth
Cloud
Internet
GMail
SaaS
Agile
PostgreSQL
SimpleNote
RTM
Heroku
NoSQL
Textmate
Dropbox
Ideas
GitHub

20. Java Tech. Background
WAR
EAR
WAR
EAR
WAR
App-Server
DB
SAP
LDAP
This makes sense for big companies with different apartments.
But it doesn’t make sense for a small Start-Up!

21. Ruby Tech. Background
In a typical Ruby environment there is usually ...
No SAP
No LDAP
No Oracle
No App-Server
No WAR
No EAR

22. Ruby Tech. Background
Just the App!
Application
Everything else is secondary!

23. Java Language
640 Pages

24. Java Language
Inheritance
Polymorphismus
AutoBoxing
Interfaces
Object Oriented
Annotations
Generics
static typing
Enums

25. Java Language
More language features don’t make a language
better. Just more complicated and more difficult
to learn.
Without monster tools like Eclipse it is nearly not
possible to use the language.

26. Can you write down the Java code to open this
file and output the content?
!
- Without IDE
- Without Google
text_file.txt

27. Java
import java.io.*;
!
class FileRead {
public static void main(String args[]) {
try{
FileInputStream fstream = new FileInputStream("text_file.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
while ((strLine = br.readLine()) != null) {
System.out.println (strLine);
}
in.close();
} catch (Exception e) {
System.err.println("Error: " + e.getMessage());
}
}
}

28. Ruby
puts File.read 'text_file.txt'

29. Python
f = open('text_file.txt', 'r')
Perl
open FILE, "text_file.txt" or die $!;

30. Ruby Language
Polymorphismus
Inheritance
Object Oriented
Duck typing
dynamic typing

31. Ruby Language
No Interfaces
No static types
No Generics
No Annotations

32. Java
Ruby
package xyz;
!
import xyz;
!
public class User {
!
public void sayHello(){
System.out.println(“Hello”);
}
!
class User
!
def say_hello
p “Hello”
end
!
}
end
User user = new User()
user.sayHello()
user = User.new
user.say_hello

33. Java
Ruby
package xyz;
!
import xyz;
!
class User
!
def say_hello
p “Hello”
end
public class User {
!
public void sayHello(){
System.out.println(“Hello”);
}
!
private
!
!
private String secretHero(){
return “secret hero”;
}
!
}
def secret_hero
“secret hero”
end
!
end

34. Java
public String doubleIt(String name){
result = name + “ ” + name;
return result;
}
Ruby
def double_it name
"#{name} #{name}"
end

35. Java
public String greetz(String name){
if (name != null){
result = “Hello” + name;
else {
result = “Hello”;
}
System.out.println( result );
}

36. Ruby
def greetz( name )
if !name.nil?
p "Hello #{name}"
else
p “Hello”
end
end

37. Ruby
def greetz(name)
p "Hello #{name}" if name
p “Hello” unless name
end

38. Ruby
def greetz(name = “Rob”, say_name = true)
p "Hello #{name}" if say_name
p “Hello” unless say_name
end
user.greetz(“Bob”, false)
user. greetz(“Bob”)
user. greetz()

39. Java
List<String> list = new ArrayList<String>();
!
list.add("Spiderman");
list.add("Batman");
list.add("Hulk");
!
for (String name : list){
System.out.println(name);
}

40. Ruby
names = Array.new
names << “Hans”
names << “Tanz”
names[0]
names[1]
names.first
names.last

41. Ruby
names = [‘Spiderman’, ‘Batman’, ‘Hulk’]
names.each do |name|
print “#{name}”
end

42. Ruby
hash = Hash.new
hash[“a”] = 100
hash[“b”] = 200
hash[“a”]
hash.delete(“a”)
hash.first
hash.last
hash.each {|key, value| puts "#{key} is #{value}" }
hash.each_key {|key| puts key }

43. irb

44. Ruby on Rails
Initial Release 2004
David Heinemeier Hansson
Web application framework
MIT License
http:/
/rubyonrails.org/

45. Ruby on Rails
activesupport : 3.2.8
bundler : ~>1.0
activerecord : 3.2.8
actionpack : 3.2.8
activeresource : 3.2.8
actionmailer : 3.2.8
railties : 3.2.8
http:/
/www.versioneye.com/package/rails

46. Ruby on Rails
MVC Framework
Convention over Configuration
KIS
Testable
No UI Components
You are in control

47. Ruby on Rails
REST
Stateless
Session in cookies OR database

48. Ruby on Rails
http:/
/www.myapp.com/photos
http:/
/www.myapp.com/photos/17
http:/
/www.myapp.com/photos/17/edit

49. Bundler - Gemfile
source 'https:/
/rubygems.org'
!
gem 'rails', '3.2.6'
gem 'sqlite3'
gem 'jquery-rails'
!
# Gems used only for assets and not required
# in production environments by default.
group :assets do
gem 'sass-rails', '~> 3.2.3'
gem 'coffee-rails', '~> 3.2.1'
gem 'uglifier', '>= 1.0.3'
end

50. Environments
development:
adapter: sqlite3
database: db/development.sqlite3
pool: 5
timeout: 5000
!
test:
adapter: sqlite3
database: db/test.sqlite3
pool: 5
timeout: 5000
!
production:
adapter: sqlite3
database: db/production.sqlite3
pool: 5
timeout: 5000
export RAILS_ENV=test
export RAILS_ENV=production
export RAILS_ENV=development

51. Rake
require File.expand_path('../config/application', __FILE__)
!
Myapp::Application.load_tasks
rake db:create
rake routes

52. Ruby on Rails
DEMO
live coding

53. Performance
Ruby is slower than Java!
!
... True!
But ...

54. Performance
Client
Request
Response
WEB
Server
40 %
20 %
READ, WRITE
Response
40 %
DB

55. Performance
Request
Response
1
HTML
Page
WEB
Server
N - Requests
to load
additional
Resources

56. Performance

57. Performance

58. Performance
Performance opt. for Web Apps.
Minify
Uglify
CSS Stripes
Opt. HTML
Opt. Database Access

59. Performance
http:/
/guides.rubyonrails.org/asset_pipeline.html
http:/
/tools.pingdom.com/fpt/

60. Who is using Ruby?
Ruby is just good small projects. Right?
-> Right!
Small Projects like ...

61. -> $ 800 Million worth

62. -> $ 1 Billion worth

63. Count of Open Source Projects
Java
Java
Ruby
PHP
0
12500
25000
37500
50000
4061
PHP
R
12320
R
Node.JS
23439
Node.JS
Python
43620
Python
Ruby
48034
2973

64. Ruby on Rails is very
good solution for WebApplications!

65. What is not good for?

66. It is not good for ...
Long living batch jobs
parsing 2 million documents
Use Java or C for that kind of jobs.

67. Links
http:/
/www.ruby-lang.org/en/
http:/
/rubyonrails.org
http:/
/ruby.railstutorial.org
http:/
/rubygems.org/
http:/
/www.heroku.com
http:/
/travis-ci.org

68. Links
http:/
/www.engineyard.com/
https:/
/www.dotcloud.com/
http:/
/www.CloudControl.com/
http:/
/jruby.org/
http:/
/www.ironruby.net/

69. ???