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Rapid Web Application Development using Ruby on Rails Sang Shin ●Sun Microsystems, Inc. ● javapassion.com ●

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You can try all the demos yourself! Join “Ruby, JRuby, Rails” free online course! www.javapassion.com/rubyonrails

Topics • • • • • • •

What is and Why Ruby on Rails (Rails)? Rails Basics Step by step for building “Hello World” Rails application ActiveRecord ActionController ActionView Deployment

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What is and Why Ruby on Rails (RoR)?

What Is “Ruby on Rails”? • A full-stack MVC web development framework • Written in Ruby • First released in 2004 by David Heinemeier Hansson • Gaining popularity

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“Ruby on Rails” Principles • Convention over configuration > Why punish the common cases? > Encourages standard practices > Everything simpler and smaller

• Don’t Repeat Yourself (DRY) > Repetitive code is harmful to adaptability

• Agile development environment > No recompile, deploy, restart cycles > Simple tools to generate code quickly > Testing built into the framework 6

Rails Basics

“Ruby on Rails” MVC

source: http://www.ilug-cal.org

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Step By Step Process of Building “Hello World” Rails Application

Steps to Follow 1.Create “Ruby on Rails” project > IDE generate necessary directories and files

2.Create and populate database tables 3.Create Models (through Rails Generator) > Migrate database

4.Create Controllers (through Rails Generator) 5.Create Views 6.Set URL Routing > Map URL to controller and action

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Demo: Building “Hello World” Rails Application Step by Step. http://www.javapassion.com/handsonlabs/rails_basics/#Exercise_1

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Key Learning Points • How to create a Rails project > Rails application directory structure > Concept of environments - development, test, and

production

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How to create a database using Rake How to create and populate tables using Migration How to create a model using Generator How to use Rails console 12

Key Learning Points • How to create a controller using Generator > How to add actions to a controller

• How to create a related view > How a controller and a view are related > How to create instance variables in an action and they

are used in a view

• How to set up a routing • How to trouble-shoot a problem 13

Demo: How to create an input form. http://www.javapassion.com/handsonlabs/rails_basics/#Exercise_4

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Key Learning Points • How to use form_tag and text_field helpers to create an input form • How input form fields are accessed in an action method through params

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Scaffolding

What is Scaffolding? • Scaffolding is a way to quickly create a CRUD application > Rails framework generates a set of actions for listing,

showing, creating, updating, and destroying objects of the class > These standardized actions come with both controller logic and default templates that through introspection already know which fields to display and which input types to use

• Supports RESTful view of the a Model 17

Demo: Creating a Rails Application using Scaffolding http://www.javapassion.com/handsonlabs/rails_scaffold/#Exercise_1

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Key Learning Points • How to perform scaffolding using Generator • What action methods are created through scaffolding • What templates are created through scaffolding

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ActiveRecord Basics

ActiveRecord Basics • Model (from MVC) • Object Relation Mapping library > A table maps to a Ruby class (Model) > A row maps to a Ruby object > Columns map to attributes

• Database agnostic • Your model class extends ActiveRecord::Base

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ActiveRecord Class • Your model class extends ActiveRecord::Base class User < ActiveRecord::Base end

• You model class contain domain logic class User < ActiveRecord::Base def self.authenticate_safely(user_name, password) find(:first, :conditions => [ "user_name = ? AND password = ?", user_name, password ]) end end

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Naming Conventions • Table names are plural and class names are singular > posts (table), Post (class) > students (table), Student (class) > people (table), Person (class)

• Tables contain a column named id

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Find: Examples • find by id Person.find(1)

# returns the object for ID = 1

Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6)

• find first

Person.find(:first) # returns the first object fetched by SELECT * FROM peop Person.find(:first, :conditions => [ "user_name = ?", user_name]) Person.find(:first, :order => "created_on DESC", :offset => 5)

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Dynamic attribute-based finders • Dynamic attribute-based finders are a cleaner way of getting (and/or creating) objects by simple queries without turning to SQL • They work by appending the name of an attribute to find_by_ or find_all_by_, so you get finders like > Person.find_by_user_name(user_name) > Person.find(:first, :conditions => ["user_name = ?", user_name]) > Person.find_all_by_last_name(last_name) > Person.find(:all, :conditions => ["last_name = ?", last_name]) > Payment.find_by_transaction_id 25

ActiveRecord Migration

ActiveRecord Migration • Provides version control of database schema > Adding a new field to a table > Removing a field from an existing table > Changing the name of the column > Creating a new table

• Each change in schema is represented in pure Ruby code

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Example: Migration • Add a boolean flag to the accounts table and remove it again, if you’re backing out of the migration. class AddSsl < ActiveRecord::Migration def self.up add_column :accounts, :ssl_enabled, :boolean, :default => 1 end def self.down remove_column :accounts, :ssl_enabled end end

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Demo: How to add a field to a table using Migration http://www.javapassion.com/handsonlabs/rails_scaffold/#Exercise_2

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Key Learning Points • How to add a new field to a table using Migration • How to create a migration file using Generator • How to see a log file

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ActiveRecord Validation

ActiveRecord::Validations • Validation methods class User < ActiveRecord::Base validates_presence_of :username, :level validates_uniqueness_of :username validates_oak_id :username validates_length_of :username, :maximum => 3, :allow_nil validates_numericality_of :value, :on => :create end 32

Validation

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Demo:

Validation http://www.javapassion.com/handsonlabs/rails_scaffold/#2.4

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ActiveRecord:: Associations

Associations • Associations are a set of macro-like class methods for tying objects together through foreign keys. • They express relationships like "Project has one Project Manager" or "Project belongs to a Portfolio". • Each macro adds a number of methods to the class which are specialized according to the collection or association symbol and the options hash. • Cardinality > One-to-one, One-to-many, Many-to-many 36

One-to-many • Use has_many in the base, and belongs_to in the associated model class Manager < ActiveRecord::Base has_many :employees end class Employee < ActiveRecord::Base belongs_to :manager # foreign key - manager_id end 37

Demo: Association http://www.javapassion.com/handsonlabs/rails_activerecord/

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ActionController Basics

ActionController • Controller is made up of one or more actions that are executed on request and then either render a template or redirect to another action • An action is defined as a public method on the controller, which will automatically be made accessible to the webserver through Rails Routes • Actions, by default, render a template in the app/views directory corresponding to the name of the controller and action after executing code in the action.

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ActionController • For example, the index action of the GuestBookController would render the template app/views/guestbook/index.erb by default after populating the @entries instance variable. class GuestBookController < ActionController::Base def index @entries = Entry.find(:all) end def sign Entry.create(params[:entry]) redirect_to :action => "index" end end

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Deployment

Web Servers • By default, Rails will try to use Mongrel and lighttpd if they are installed, otherwise Rails will use WEBrick, the webserver that ships with Ruby. • Java Server integration > Goldspike > GlassFish V3

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Goldspike • Rails Plugin • Packages Rails application as WAR • WAR contains a servlet that translates data from the servlet request to the Rails dispatcher • Works for any servlet container • rake war:standalone:create

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Demo:

Deployment through Goldspike http://www.javapassion.com/handsonlabs/rails_deploy/#Exercise_1

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JRuby on Rails

Why “JRuby on Rails” over “Ruby on Rails”? • Java technology production environments pervasive > Easier to switch framework vs. whole architecture > Lower barrier to entry

• Integration with Java technology libraries, legacy services • No need to leave Java technology servers, libraries, reliability • Deployment to Java application servers 47

“JRuby on Rails”: Java EE Platform • Pool database connections • Access any Java Naming and Directory Interface™ (J.N.D.I.) API resource • Access any Java EE platform TLA: > Java Persistence API (JPA) > Java Management Extensions (JMX™) > Enterprise JavaBeans™ (EJB™) > Java Message Service (JMS) API > SOAP/WSDL/SOA 48

Rapid Web Application Development using Ruby on Rails Sang Shin ●Sun Microsystems, Inc. ● javapassion.com ●

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