Grails Web app development with pleasure

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GrailsWeb app development with pleasure!

• Guillaume Laforge
• Vice-President, Technology
• G2One, Inc.
• http//www.g2one.com

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Goal of This Talk
Discovering the Grails web framework
Learn more about Grails, how easily you can use
it in your projects, and how to get back the
pleasure of web development!
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Guillaume Laforge

• Groovy Project Manager
• JSR-241 Spec Lead
• Initiator of the Grails framework
• Co-author of Groovy in Action
• By Dierk König, et al.
• Vice-President Technology

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Agenda

• Whats Grails?
• The Problem with the usual web frameworks
• The different layers
• Other cool features
• The plugin system
• Summary
• QA

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Whats Grails?

• From 10,000 feet
• From 1,000 feet
• Near the ground

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Whats Grails? (1/3)

• From 10,000 feet
• Grails is an MVC action-based framework
• Principles
• CoC Convention over Configuration
• DRY Dont Repeat Yourself
• The essence of Ruby on Rails, but with the tight
  integration with the Java ecosystem
• Protect your investment!

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Whats Grails? (2/3)

• From 1,000 feet

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Whats Grails? (3/3)

• Near the ground
• Grails is built on proven solid OSS bricks
• Spring IoC, DI, Spring MVC, transactions
• Hibernate ORM, querying mechanism
• Groovy for everything that matters
• SiteMesh page layout and composition
• Quartz for job scheduling
• AJAX integration with different libraries
• Jetty HSQLDB for fast development cycles

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The Grails Stack
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Why Groovy?

• Java-like syntax
• Flat learning curve
• The same programming models
• Same OO, security, threading models
• The same libraries
• JDK, and any in-house or OSS JAR
• And Groovy has
• Closures, properties, malleable syntax for DSLs

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The Problem

• Whats the problem with Web frameworks?
• Why has it got to be complex?
• What are the pain points?

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Has it got to be complex?

• Struts / Spring / Hibernate is okay

• But its slow to start with
• Seting up the project takes time
• It gets complicated pretty rapidly
• Dive into Spring Hibernate to wireeverything
  together
• There are so many layers
• DAOs, DTOs, more abstraction layers
• Too many configuration files
• Often too much XML for everything

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The Pain Points

• ORM persistence overly hard to master and get
  right
• Numerous layers and configuration files lead to
  chaos
• Ugly JSPs with scriptlets and the complexity of
  JSP tags
• Grails addresses the fundamental flaws in Java
  web application development today without
  compromising the platform

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The Different Layers

• Bottom-up!
• Transparent persistence
• Controllers and services
• Groovy Server Pages, templates taglibs

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Grails MVC at a Glance

• Model
• GORM Grails Object Relational Mapping
• Controller
• Multi-action controller
• Also the Service layer Quartz job scheduling
• View
• GSP Groovy Server Pages
• Tag libraries

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Pain Point 1 Peristence

• ORM is quite hard to master and get right
• Many configuration files

hibernate.cfg.xml
ejb-cmp.xml
ibatis.xml
persistence.xml
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GORM Grails Object Relational Mapping

• Hibernate under the hood
• Domain model is a set of POGOs
• Plain Old Groovy Objects
• POGOs are transparently mapped!
• No hibernate.cfg.xml
• But can be overriden if needed
• All domain classes get useful instance and static
  methods for free
• Book.count(), Book.list(), Book.get(id)
• book.save(), book.delete(), book.update()

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Example

• Grails provides a default ORM mapping strategy
  for Hibernate

// A Book domain class class Book String
title Date releaseDate static belongsTo
author Author // A one-to-many class User
String name static hasMany
bookmarks Bookmark
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ltDEMO/gt
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Constraints

• Constraints are added in domain classes through a
  static constraint field
• static constraint isbn(matches
  "0-990-9X")
• Many constraints available
• blank, creditcard, email, blank, nullable,
  matches, range, unique, url
• You can create your own validator
• myField(validator it 2 0 )

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No more DAOs!

• Dynamic finder methods
• Book.findByTitle("The Stand") Book.findByTitleLik
  e("Harry Pot") Book.findByReleaseDateBetween(sta
  rt, end) Book.findByTitleLikeOrReleaseDateLessTha
  n( "Grails", someDate)
• Find by relationship
• Book.findAllByAuthor( Author.get(1) )
• Affect sorting
• Book.findAllByAuthor( me, sort title, order
  asc )

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Querying

• Query by example
• Book.find ( new Book(title The Shining) )
• HQL queries
• Book.find(" from Book b where b.title like Lord
  of ")
• Book.find(" from Book b where b.title like ? ",
  Lord of)
• Criteria builder
• def results Account.createCriteria()
  like("holderFirstName", "Fred") and
  between("balance", 500, 1000)
  eq("branch", "London") order("holderLastNa
  me", "desc") .list()

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Pain Point 2 Services, Nav. Pres. Logic

• Numerous layers
• Conf file chaos

faces-config.xml
struts-config.xml
xwork.xml
web.xml
applicationContext.xml
sitemesh.xml
tiles.xml
validator.xml
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Controllers

• class BookController
• def index redirect(actionlist,paramsparams
  )
• def list bookList Book.list( params )
  
• def show book Book.get( params.id )
• def edit
• def book Book.get( params.id )
• if(!book)
• flash.message "Book params.id not
  found"
• redirect(actionlist)
• else return book book
• http//localhost8080/myapp/book/show

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Services Scheduled Tasks

• Services are Groovy classes that should contain
  your business logic
• Automatic injection of services in controllers
  services simply by declaring a field
• class BookController MySuperService
  mySuperService
• Recuring events (Quartz)
• Intervals, or cron definitions
• class MyJob def cronExpression "0 0 24
  ?" def execute() print "Job
  run!"

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Pain Point 3 The View Layer

• JSP cluttered with scriptlets
• Taglibs are painful

spring.tld
c.tld
struts.tld
fmt.tld
grails.tld
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The view layer

• Spring MVC under the hood
• Support for flash scope between requests
• GSP Groovy alternative to JSP
• Dynamic taglib development
• ? no TLD, no configuration, just conventions
• Adaptive AJAX tags
• Yahoo, Dojo, Prototype
• Customisable layout with SiteMesh
• Page fragments through reusable templates
• Views under grails-app/views

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Groovy Server Pages

• lthtmlgt
• ltheadgt
• ltmeta name"layout" content"main" /gt
• lttitlegtBook Listlt/titlegt
• lt/headgt
• ltbodygt
• lta href"createLinkTo(dir'')"gtHomelt/agt
  
• ltglink action"create"gtNew Booklt/glinkgt
• ltgif test"flash.message"gt
• flash.message
• lt/gifgt
• ltgeach in"bookList"gtit.titlelt/gea
  chgt
• lt/bodygt
• lt/htmlgt

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Dynamic Tag Libraries

• Logical if, else, elseif
• Iterative while, each, collect, findAll
• Linking link, createLink, createLinkTo
• Ajax remoteFunction, remoteLink, formRemote,
  submitToRemote
• Form form, select, currencySelect, localeSelect,
  datePicker, checkBox
• Rendering render, layout, paginate
• Validation eachError, hasError, message
• UI richTextEditor

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Write your Own Taglib

• Yet another Grails convention
• class MyTagLib def isAdmin attrs, body
  -gt def user attrs'user'
  if(user ! null checkUserPrivs(user))
  body()
• Use it in your GSP
• ltgisAdmin user"myUser"gt some restricted
  contentlt/gisAdmingt

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What else?

• Custom URL mapping
• Conversation flows
• ORM DSL
• http//grails.org/GORM-MappingDSL
• Develop with pleasure with IntelliJ IDEA
• http//grails.org/IDEAIntegration

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Custom URL Mappings (1/2)

• Pretty URLs in seconds
• Custom DSL for mapping URLs to controllers,
  actions and views
• Supports mapping URLs to actions via HTTP
  methods for REST
• Supports rich constraints mechanism

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Custom URL Mappings (2/2)

• Pretty URLs in seconds!
• class UrlMappings static mappings
  "/product/id"(controller "product",
  action "show") "/blog/year?/month?
  /day?"(controller "blog",
  action "show") constraints
  year(matches /\d4/)

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Conversations flows (1/2)

• Leverages Spring WebFlow
• Supports Springs scopes
• Request
• Session
• Conversation
• Flash
• Possibly to specify services scope
• DSL for constructing flows

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Conversations flows (2/2)

• Example
• def searchFlow displaySearchForm
  on("submit").to "executeSearch"  
  executeSearch action results
  searchService.
  executeSearch(params.q)
  on("success").to "displayResults"
  on("error").to "displaySearchForm" 
  displayResults()

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Grails plugin system

• Beyond the out-of-the-box experience,
• extend Grails with plugins
• and write your own!

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Plugin Extension Points

• Extend Grails beyond what it offers!
• What can you do with plugins?
• Hook into the build system
• Script the Spring application context
• Register new dynamic methods
• Container configuration (web.xml)
• Adding new artefacts types
• Auto-reload your artefacts

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Plenty of Plugins!

• XFire
• Expose Grails services as SOAP
• Searchable
• Integrate Lucene Compass search
• Remoting
• Expose Grails services over RMI, Burlap, or REST
• Google Web Toolkit
• Integrate Grails with GWT for the presentation
  layer
• Acegi / JSecurity
• Secure your Grails app
• JMS
• Expose services as message-driven beans

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Sweet spotEnterprise-readiness

• Skills, libraries, app servers

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Protect your Investment

• Reuse
• Existing Java libraries (JDK, 3rd party,
  in-house)
• Employee skills knowledge (both prod soft)
• Spring configured beans
• Hibernate mappings for legacy schemas (but still
  benefit from dynamic finders)
• EJB3 annotated mapped beans
• JSPs, taglibs for the view
• Deploy on your pricey Java app-server database
• Grails will fit in your Java EE enterprise
  architecture!

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Lets Wrap Up

• Summary
• Resources
• QA

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Summary

• Groovy is a powerful dynamic language for the
  JVM, that provides agile development on the Java
  platform, without the impedance mismatch of other
  languages
• ? Groovy 1.1 out next week
• Grails is a fully-featured web application
  framework based on proven technologies like
  Spring and Hibernate, which simplifies the
  development of innovative applications
• ? Grails 1.0 at the end of the month

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Resources

• Grails http//grails.org
• Groovy http//groovy.codehaus.org
• Groovy blogs http//groovyblogs.org
• AboutGroovy http//aboutgroovy.com
• Mailing-lists http//grails.org/Mailinglists
• G2One http//www.g2one.com

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G2One, Inc.

• Groovy Grails at the source!
• Graeme Rocher, Grails lead
• Guillaume Laforge, Groovy lead
• Plus key committers
• Professional Services
• Training, support, consulting
• Custom developments
• Connectors, plugins, etc

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QA