java, ruby & rails

C O N N E C T I N G B U S I N E S S & T E C H N O L O G Y

Java, Ruby & RailsJava, Ruby & Rails

http://www.devoteam.se/index.php


2009-03-18

2 C O N N E C T I N G B U S I N E S S & T E C H N O L O G Y

The Java platform

“It’s all about the Java Virtual Machine. That’s the integration hub.” Gosling, Sun Tech Days 2007Lots of new languages for the JVM Scala, Clojure, Groovy, Jython, (J)Ruby, JavaScript

(Rhino), JavaFXThe DaVinci Machine JSR-292 Target JDK 7 invokedynamic instruction


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Why Ruby?

Ubiquity C-Ruby (MRI) JRuby IronRuby (.NET) Rubinius, Maglev, YARV

Scripting java shebang/backticks

Rails FrameworkSupport from Sun, ThoughtworksMost likely to succeed?


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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 surpriseRuntime efficiency not a top priority“More powerful than Perl, more OO than Python”MRI is the specification RubySpec is in the works


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Ruby Characteristics

InterpretedObject oriented ”myString”.upcase 2_500.+2 44.modulo 5

ReflectiveGarbage collectedDuck typing If it walks like a duck and quacks like a duck it must be a duck


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Dynamic features

Reopen existing classes redefine methods “monkeypatching”

Meta-programmingMethod aliasing alias_method :validates_size_of, :validates_length_of

method_missing Eg provide a generic sort method sort_by_x

Closures


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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


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Ruby anatomy

Classes are CamelCasedMethods are under_scoredGenerally 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


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Example


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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 Modulesearches $LOAD_PATH


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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


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Testing

Test::Unit::TestCase xUnit for ruby

JRuby to test Java code? JtestR to invoke Code coverage

might be an issueRSpec BDD


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Method signature - Java

Method overloadingNumber of method signatures increases fast if flexibility is wanted


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Method signature – PL/SQL

Named parametersStill have to change method signature too add parameters


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Method signature – Ruby

Hash as optional parameter, not named parametersNo need to change method signatureHash doesn’t need curly bracesMethod overload unavailable*args => arguments array


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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


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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


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RoR principles

Opinionated softwareConvention over configurationDRYREST 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


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Ruby on Rails concepts

rails <appname> generates skeleton routes.rb ~struts-config.xml*.html.erb ~JSPGenerators 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)


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RoR tools

rails <appname> -d <database>script/generate scaffold Person name:stringscript/serverscript/console irb with access to the application

script/dbconsole enter SQL

script/server –debugger debugger in the code drops to console


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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


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RoR model example

class BlogPost < ActiveRecord::Base belongs_to :author has_many :comments validates_presence_of :titleend

comments table needs blog_post_idblog_posts table needs author_idNew post need title field


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A/R Metaprogramming


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ActiveSupport::TestCase

Inherits Test::Unit::TestCase Provides helpers, eg http calls

<app>/test functional integration unit

fixtures/fixtures.ymlrake


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Jruby Motivation

The JVMSneak into the enterpriseReuse infrastructureIntegrate with Java applicationsPerformance and scalability


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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)


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Java integration

include Java / require ”java”include Java::JavaxSwinginclude_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


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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


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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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Thank you and Namaste


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Contact

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