Java, Ruby & Rails

The Java platform “ It’s all about the Java Virtual Machine. That’s the integration hub.” Gosling, Sun Tech Days 2007 Lots of new languages for the JVM Scala, Clojure, Groovy, Jython, (J)Ruby, JavaScript (Rhino), JavaFX The DaVinci Machine JSR-292 Target JDK 7 invokedynamic instruction

Why Ruby? Ubiquity C-Ruby (MRI) JRuby IronRuby (.NET) Rubinius, Maglev, YARV Scripting java shebang/backticks Rails Framework Support from Sun, Thoughtworks Most likely to succeed?

What is Ruby? Created by Yukihiro Matsumoto (Matz) in 1993 “ A dynamic, open source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write.” The principle of least surprise Runtime efficiency not a top priority “ More powerful than Perl, more OO than Python” MRI is the specification RubySpec is in the works

Ruby Characteristics Interpreted Object oriented ” myString”.upcase 2_500.+2 44.modulo 5 Reflective Garbage collected Duck typing If it walks like a duck and quacks like a duck it must be a duck

Dynamic features Reopen existing classes redefine methods “ monkeypatching” Meta-programming Method aliasing alias_method :validates_size_of , :validates_length_of method_missing Eg provide a generic sort method sort_by_x Closures

Core Ruby tools (j)ruby the interpreter (j)irb interactive ruby, ~readline support, tab completion ri ruby interactive ~man pages rdoc html doc ~javadoc rake ant/make for ruby gem package manager

Ruby anatomy Classes are CamelCased Methods are under_scored Generally no need for curly braces, parentheses, semicolon or return statement code more compact Comments =begin block comment =end # line comment Variables Constant @@classVariable @instanceVariable localVariable :symbol

Ruby structure Modules Module::Class Mix-ins interfaces with functionality Namespace Subclass < Superclass Single inheritance only Files are named *.rb can hold many classes require ’file’ include Module searches $LOAD_PATH

Access modifiers private Private to this instance (might be a subclass) You can’t specify the receiver, not even self protected Can be called by instances of the same class Eg use for comparators public FFA private :method or private (until end) The modifiers are methods, not keywords

Testing Test::Unit::TestCase xUnit for ruby JRuby to test Java code? JtestR to invoke Code coverage might be an issue RSpec BDD

Method signature - Java Method overloading Number of method signatures increases fast if flexibility is wanted

Method signature – PL/SQL Named parameters Still have to change method signature too add parameters

Method signature – Ruby Hash as optional parameter, not named parameters No need to change method signature Hash doesn’t need curly braces Method overload unavailable *args => arguments array

More syntax examples =~ regexp matcher myString =~ /[0-9]+/ %w[] String array myArray = %w[ruby java haskell] {||} or do || end closures (and embedded variables) myHash.each { |k, v| puts k+’ is ‘+v } myHash.each do |key, val| puts “#{key} is #{val}” end

Ruby on Rails MVC Framework “ Rails is the most well thought-out web development framework I’ve ever used. And that’s in a decade of doing web applications for a living. I’ve built my own frameworks, helped develop the Servlet API, and have created more than a few web servers from scratch. Nobody has done it like this before.” -James Duncan Davidson, Creator of Tomcat and Ant “ Rails is the killer app for Ruby.” Yukihiro Matsumoto, Creator of Ruby

RoR principles Opinionated software Convention over configuration DRY REST GET /products #get all GET /products/42 #get id=42 POST /products #create Fast feedback loop just reload, no compile Rails itself is a gem

Ruby on Rails concepts rails <appname> generates skeleton routes.rb ~struts-config.xml *.html.erb ~JSP Generators Generates model, view, controller, tests Partials (html.erb snippets) Plugins (instead of gems) Default database is sqlite3 (via JDBC for JRuby) Filters (defined in controller)

RoR tools rails <appname> -d <database> script/generate scaffold Person name:string script/server script/console irb with access to the application script/dbconsole enter SQL script/server –debugger debugger in the code drops to console

ActiveRecord O/R mapping Db migrations, dev, test, prod up and down database agnostic rake db:migrate config/database.yml Opinionated software primary key named id pluralization class Book => db books

RoR model example class BlogPost < ActiveRecord::Base belongs_to :author has_many :comments validates_presence_of :title end comments table needs blog_post_id blog_posts table needs author_id New post need title field

ActiveSupport::TestCase Inherits Test::Unit::TestCase Provides helpers, eg http calls <app>/test functional integration unit fixtures/fixtures.yml rake

Jruby Motivation The JVM Sneak into the enterprise Reuse infrastructure Integrate with Java applications Performance and scalability

JRuby on Rails Develop as Java Netbeans Eclipse Integrate with Java Call EJBs Use JMS queues Use JNDI Use JAAS Deploy on Java As *.war using warbler Rails deployer (JBoss, Glassfish)

Java integration include Java / require ”java” include Java::JavaxSwing include_class "javax.naming.InitialContext” require ”path/to/my.jar” prefix javaclasses to avoid name collisions String => JString include_class 'java.lang.String’ {|package,name| "J#{name}" } Method alias System.currentTimeMillis => System.current_time_millis Getters and setters behaves like attr_accessor fields

IDE support Eclipse - DLTK (Dynamic Languages Toolkit) Eclipse foundation plugin Support for TCL, Python, Ruby No Rails Eclipse - Aptana RadRails RDT Ruby Editor Rails support generators/scripts Visual debug Testrunner Netbeans Official plugin

Conclusion Ruby is sweet! Syntactic sugar Fun to work with Ruby is useful! Integrate with Java OO scripting Rails is probably fast enough Ruby is hard! “ Good programmers become better, bad programmers become worse” Test, test, test

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