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Grails Web app development with pleasure

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Learn more about Grails, how easily you can use it in your projects, ... Co-author of Groovy in Action. By Dierk K nig, et al. Vice-President Technology. Agenda ... – PowerPoint PPT presentation

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Title: Grails Web app development with pleasure


1
GrailsWeb app development with pleasure!
  • Guillaume Laforge
  • Vice-President, Technology
  • G2One, Inc.
  • http//www.g2one.com

2
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!
3
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

4
Agenda
  • Whats Grails?
  • The Problem with the usual web frameworks
  • The different layers
  • Other cool features
  • The plugin system
  • Summary
  • QA

5
Whats Grails?
  • From 10,000 feet
  • From 1,000 feet
  • Near the ground

6
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!

7
Whats Grails? (2/3)
  • From 1,000 feet




8
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

9
The Grails Stack
10
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

11
The Problem
  • Whats the problem with Web frameworks?
  • Why has it got to be complex?
  • What are the pain points?

12
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

13
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

14
The Different Layers
  • Bottom-up!
  • Transparent persistence
  • Controllers and services
  • Groovy Server Pages, templates taglibs

15
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

16
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
17
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()

18
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
19
ltDEMO/gt
20
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 )

21
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 )

22
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()

23
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
24
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

25
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!"

26
Pain Point 3 The View Layer
  • JSP cluttered with scriptlets
  • Taglibs are painful

spring.tld
c.tld
struts.tld
fmt.tld
grails.tld
27
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

28
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

29
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

30
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

31
What else?
  • Custom URL mapping
  • Conversation flows
  • ORM DSL
  • http//grails.org/GORM-MappingDSL
  • Develop with pleasure with IntelliJ IDEA
  • http//grails.org/IDEAIntegration

32
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

33
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/)

34
Conversations flows (1/2)
  • Leverages Spring WebFlow
  • Supports Springs scopes
  • Request
  • Session
  • Conversation
  • Flash
  • Possibly to specify services scope
  • DSL for constructing flows

35
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()

36
Grails plugin system
  • Beyond the out-of-the-box experience,
  • extend Grails with plugins
  • and write your own!

37
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

38
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

39
Sweet spotEnterprise-readiness
  • Skills, libraries, app servers

40
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!

41
Lets Wrap Up
  • Summary
  • Resources
  • QA

42
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

43
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

44
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

45
QA
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