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2006 JavaOneSM Conference | Session BOF-2521 |

Rapid Web Application Development with Grails

Graeme RocherManaging DirectorAgilize ithttp://www.agilizeit.com

Session ID# BOF-2521

2006 JavaOneSM Conference | Session BOF-2521 | 2

Learn how to rapidly create web applications using the agile web application framework Grails

Rapid Web Application Development with GrailsGoal of this Talk


Agenda

Groovy & GrailsGetting StartedThe Application DomainControllersGroovy Servers Pages (GSP)Tag LibrariesAjax SupportScaffoldingJava Integration


Agenda



Groovy & Grails

● Grails: MVC web framework inspired by:● Convention over Configuration● Don’t Repeat Yourself (DRY)● Ruby on Rails

● Built on solid foundations:● Spring IoC, MVC and WebFlow● Hibernate● SiteMesh

● Why Groovy?● Meta-Programming● Closure Support● Syntactically Expressive● Java Integration

Source: Please add the source of your data here


Agenda



Getting Started

● Grails available from http://grails.org● Stable & Development snapshots available● Simple installation:

● Download & extract zip● Set GRAILS_HOME variable● Add $GRAILS_HOME\bin to PATH variable

● Run “grails create-app”



+ PROJECT_HOME+ grails-app

+ conf+ controllers+ domain+ i18n+ services+ taglib+ views

+ lib+ spring+ hibernate+ src+ web-app

Project Infrastructure

Main Grails resources

Additional Spring configuration

Additional Hibernate mapping

Web resources e.g. CSS, JavaScript etc.

Java sources

Jar archive libraries


Command Line Targets

● Apache Ant bundled with Grails● Many useful targets available:

● create-* (for creating Grails artifacts)● generate-controller● generate-views● run-app● test-app● run-webtest



The Data Source

// data source located in grails-app/conf

Class ApplicationDataSource {

@Property pooled = false

@Property dbCreate = “create-drop”

@Property url = “jdbc:hsqldb:mem:testDb”@Property driverClassName = “org.hsqldb.jdbcDriver”@Property username = “sa”@Property password = “sa”

}

Whether connectionPooling is enabled

DB Auto creation withhbm2ddl

Remaining connectionsettings


Agenda



The Application Domain

● Domain classes hold state and implement behaviour

● They are linked together via relationships (e.g. one-to-many)

● In Java domain classes have traditionally been handled by Object-Relational Mapping (ORM)

● Grails provides simple ORM built on Hibernate



Grails ORM (GORM)● Extremely simple. No special class to extend or file to configure!

class ExpenseReport {

@Property Long id

@Property Long version

@Property relatesToMany = [items:ExpenseItem]

@Property Set items

@Property Date submissionDate

@Property String employeeName

}

Each domain class has an ‘id’ and ‘version’

Defines one-to-manyrelationship

to ExpenseItem


Grails ORM (GORM)● We’ve got this far, so lets define the other side!

class ExpenseItem {

@Property Long id

@Property Long version

@Property belongsTo = ExpenseReport

@Property String type

@Property Currency currency

@Property Integer amount

}

Defines the owningside of the relationship

Each property mapsTo a column


Grails Constraints

● Validation constraints can be defined using the ‘constraints’ property

class ExpenseItem {

…

@Property constraints = {type(inList:['travel', 'accomodation'])

amount(range:1..999)

}

}

Each node relates to a property

Ensures the ‘type’ propertyIs one of the values in the list‘amount’ must be

in a range greater than 0but less than 1000


Dynamic Methods & Properties

● Grails injects methods and properties into domain classes at runtime:

def r = ExpenseReport.findByEmployeeName('fred')

def r = ExpenseReport

.findBySubmissionDateGreaterThan(lastMonth)

def reports = ExpenseReport.findAll()

assert ! (new ExpenseItem().validate())

def er = new ExpenseReport(employeeName: 'Edgar')

.save()


Agenda



Controllers

● Controllers handle requests and prepare responses

● Response created by either delegating to a view or writing to the response

● A controller is a class containing closure properties that act on requests

● The convention used for the name of the controller and the actions within map to URIs.



The Controller

● The controller and action name map to the URI: /expenseReport/list

class ExpenseReportController {

@Property list = {

[expenseReports : ExpenseReport.list()]

}

}

The name of theclass is the firsttoken in the URI

Each action is aclosure property

An optional modelis returned as a

map


Data Binding & Flow Control

// save action

@Property save = {

def e = ExpenseItem.get(params.id)

e.properties = params

if(e.save()){

redirect(action:show,id:e.id)

} else {

render( view: 'create',

model:[expenseItem:e] )

}

}

Auto-type conversionfrom request parameters

Dynamic get methodAuto-type conversion

To id type

Example flow control

via render andredirect methods


Agenda



Groovy Server Pages

● A view technology very similar to JSP, but with Groovy as the primary language

● More expressive and concise with support for embedded GStrings & Tags

● Layout support through integration with SiteMesh

● Ability to define dynamic tag libraries


A GSP Example

● The GSP for the list action is named according to convention: grails-app/views/expenseItem/list.gsp

<html>

<body>

<g:each in="${expenseItems}">

${it.type} – amount: ${it.amount}

</g:each>

</body>

</html>

References the modelreturned by the

controller

Embedded GStringexpressions


Agenda

Groovy & GrailsGetting StartedThe Application DomainControllersGroovy Servers PagesTag LibrariesAjax SupportScaffoldingJava Integration

Dynamic Tag Libraries

● Easy definition of simple, logical and iterative tags:

class ExpenseTagLib {

@Property dateFormat = { attrs,body ->

out << new SimpleDateFormat(attrs.format)

.format(attrs.date)

}

}

The name of thetag

The body argument is a closure that can be invoked

The attributes arepassed as a map

Dynamic Tag Libraries

● Using the tag requires no imports or configuration and can be reloaded at runtime!:

Submitted:

<g:dateFormat date="${report.submissionDate}"

format="DD-MM-YYYY" />



<input type="hidden" name="submissionDate"

value="${dateFormat(

date:report.submissionDate,

format:'DD-MM-YYYY')}" />



Tag called by namewith the “g:” prefix

Tag can also becalled as a regular

method!


Agenda

Groovy & GrailsGetting StartedThe Application DomainControllersGroovy Servers PagesTag LibrariesAjax SupportScaffoldingJava Integration


AJAX Support

● Built in “adaptive” tag library for Ajax● Supports Prototype, Rico, and Yahoo (Dojo

coming soon)● Tags for remote linking, asynchronous form

submission etc.● Dynamic “render” method available for

rendering XML snippets, or partial templates● Save/Reload and dynamic tag libraries make

Ajax even easier


Agenda

Groovy & GrailsGetting StartedThe Application DomainControllersGroovy Servers PagesTag LibrariesScaffoldingAjax SupportJava Integration


DEMOScaffolding


Agenda

Groovy & GrailsGetting StartedThe Application DomainControllersGroovy Servers PagesTag LibrariesScaffoldingAjax SupportJava Integration


Java Integration

● Now for the important bit, with Groovy and Grails you can:

● Call any existing Java library seamlessly● Deploy as a WAR onto any JEE application

server● Write your domain model in Java, mapped with

Hibernate, and still use dynamic methods!● Take advantage of Hibernate’s power by

mapping onto legacy systems.● Use Spring’s dependency injection to integrate

Controllers with existing services


DEMOECLIPSE INTEGRATION


Summary

● With the advent on Web 2.0 agility is key● Dynamic frameworks (Grails, Rails, Django etc.)

provide this through quick iterative development with a clear productivity gain

● However, for large scale applications static-typing and IDE support is crucial

● Grails provides the ability to use a blended approach

● And most importantly it runs on the JVM!


For More Information

● Groovy website – http://groovy.codehaus.org● Grails website – http://grails.org● Mailing lists – http://grails.org/Mailing+lists● Graeme’s Blog – http://graemerocher.blogspot.com● Upcoming books ‘The Definitive Guide to Grails’ by

Apress and ‘Groovy in Action’ by Manning


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