Grails

Mansura Habiba13 november 2011

Introduction

What is Grails?Runs on the Java Virtual MachineUsed Java like dynamic language Groovy Inspired by Rubi on railsCreated and used by Google

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Feature of Grails

• Grails is a rapid web application development framework built on Groovy and Spring

• Grails has full stack environement• Grails is modular and extensible through a

plugin system• Just like Spring Grails deployed in any

environment

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Stack

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JAVA Virtual Machine

JAVA EE JDK Servlet Apache Common Groovy

SiteMesh

SpringMVC, Beans,

Txns

GORM

Hibernet

HSQLBD

Gan

t (G

roo

vy A

nt)

JUnit

Grails

Controller

View (gsp) Service Domainplugin

Full Stack Web Framework

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Web MVC GSP Viewes Servlet Container

Database I18n

Test Support Doc Engine

GORM (Data Access)

Build

An easy to use MVC Framework

Embedded ServletSimple but Powerful

Build in DB access and Modelling

In Memory SQL Database

Build in Internationalizartion

WiKi based HTML Doc Engine

Grails MVC Framework

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Spring Dispatcher Servlet

Grails Dispatcher Servlet

Simple Grails Controller

Simple Grails Controller Helper

User Interface (GSP)

Grails Controller Grails Service/ Plug-ins

Grails DomainDB

GORM

Template (Sitemesh)

Extends

URI Request

URI Request

View

Model & View

mapping

Comparison of Groovy with Ruby and Java

Consideration Java ( JVM ?)

Ruby on Rails

Groovy and Grails

Reduced Time to Market No Yes Yes

Reduced Costs No Yes Yes

Long term scalability Yes No Yes

Recommended for applications currently on Java and PHP

Yes No Yes

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Consideration Java ( JVM ?) Ruby on Rails Groovy and Grails

Lines of codes to write (Prototypical form validation example)

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Readability Lengthy lines of codes make it less readable

Small size helps in readability Good IDE support and hence increases readability.Also size of code governs readability

Performance High Comparitively lower than Java and Grails

Higher than RoR but lesser than Java

Well-structured and updated knowledge base

Yes No Yes

Adaptability with Agile No Yes YesEnterprise support Yes Small applications.

The support of enterprise technologies is not at the focus of the community

Could be used for prototyping and also for real applications

In built testing tools available No Yes Yes

Developer availability Huge supply Not as much compared to Java

Groovy is a natural transition for Java developers

Scalability Yes No YesRichness of API/libraries available

Yes No Yes

Ability to embed in desktop (Java/C++) applications

Yes No Yes

Ease of deployment No Yes YesLearning curve Yes Depends on the history of the

developer.Generally start with the database schema and generate domain objects, view and controller from there

Depends on the history of the developer.Start with the domain objects and generate view, controller and database schema.A lot more people can write proper domain classes than proper database schemata.

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Installation (JDK)

• Download JDK from the following Url• Invoke the installer and follow the

installation• Setup JAVA_HOME as User variable• Add % JAVA_HOME %\bin to Path

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Installation (Grails)

• Download GGTS from the following link http://spring.io/tools/ggts

• Unzip the binary• Plug and play

– No need to set up GRAILS_HOME– No need to modify Path varible– No need to set up Server

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Grails Installation Folder

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IDE

Grails

Server Open Source Licence

Create a Web Application

grails create-app HelloWorld

install-plugin spring-security-

core

s2-quickstart com.grails.tutoria

l User Role

Add properties to generated User

Class

grails generate-all

com.grails.tutorial .User

grails run-app

Application will be available at

http://localhost:8080/HelloWorld

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Grails Web Application: Important files

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Grails Web Application: Url mapping

• Custome DSL for Mapping URLs to view, controller, action

• Support rich constraints for mechanism• Support HTTP method for REST

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Grails Web Application: Url mapping

Grails & validation

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class User { String login String password String emailInteger ageDate birthDate

static constraints = {login size: 5..15, blank: false, unique: true password size: 5..15, blank: falseemail email: true, blank: false age min: 18birthDate max: new Date()}

}

<g:renderErrors bean="${user}" />

<g:hasErrors bean="${user}"> <ul> <g:eachError var="err" bean="${user}"> <li>${err}</li> </g:eachError> </ul> </g:hasErrors>

<div class="fieldcontain ${hasErrors(bean: userInstance, field: 'firstname', 'error')} "><label for="firstname"><g:message code="user.firstname.label" default="Firstname" />

</label><g:textField name="firstname" value="${userInstance?.firstname}" /></div>

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Validating the data : Standerd validation

• nullable - Ensures the property value cannot be null

• blank- Prevents empty fields

• email - Checks for well-formed email addresses

• inList - Displays a combo-box

• Unique - Prevents duplicate values in the database

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• min, max - Minimum, maximum value for a numeric field

• minSize, maxSize Minimum, maximum length for a text field

• matches - Applies a regular expression against a string value

• validator - Set to a closure or

block to use as a custom validation

Grails & Internationalization

• Grails ships with several message bundles for a whole range of languages within the grails-app/i18n directory. For example:– messages.properties– messages_da.properties– messages_de.properties– messages_es.properties– messages_fr.properties

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Default

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Grails & Internationalization

• Reading Messages in the View

• Reading Messages in Controllers

• Reading Messages in Tag Libraries

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<g:message code="my.localized.content" args="${ ['Juan', 'lunes'] }" />

def show() { def msg = message(code: "my.localized.content", args: ['Juan', 'lunes']) }

def myTag = { attrs, body -> def msg = g.message(code: "my.localized.content", args: ['Juan', 'lunes']) }

Grails & Internationalization

grails-app/conf/UrlMappings.groovy

/grails-app/conf/spring/resources.groovy

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Grails & Internationalization

<g:link mapping="storeCategory" params="[lang:'en', category:'new']">Category</g:link>

Grails Plugin

• All available plugin– http://grails.org/plugins/?filter=all

• Plugins are themeselves Grails applications

• Plugins are provided with several hooks during install

• Plugin resources are added to the main application at startup

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Grails Plugin

• > grails list-plugins• > grails install-plugin <name>• > grails plugin-info <name>• > grails create-plugin

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Grails Testcase

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Most used Grails Command

– grails create-app [project_Name]– grails create-domain-class [qualified_domain_class_Name]– grails generate-all/view/controller [qualified_domain_class_Name]– grails install-plugin [plugin-name]– grails run-app– grails test-app– grails war– grails console

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Grails and Mobile Application Development

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1. Sencha/ExtJS (www.sencha.com)

2. Grails (www.grails.org)

3. MySQL (www.mysql.org)

4. Tomcat (tomcat.apache.org)

5. Apache (www.apache.org)

http://www.cubedrive.com/calendarDemo/

SOA and REST with Grails

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Why Grails is Popular

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InfoQ's Top 20 Web Frameworks for the JVM 2013

Why Grails is Popular (Cont..)

• Agile and dynamic language for the Java Virtual Machine

• Java + Additional features.• Makes modern programming features

available to Java developers with almost-zero learning curve

• Supports Domain-Specific Languages and other compact syntax so your code becomes easy to read and maintain

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Why Grails is Popular (Cont..)

• Makes writing shell and build scripts easy with its powerful processing primitives, OO abilities and an Ant DSL

• •Increases developer productivity by reducing scaffolding code when developing web, GUI, database or console applications

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Why Grails is Popular (Cont..)

• Simplifies testing by supporting unit testing and mocking out-of-the-box

• Seamlessly integrates with all existing Java objects and libraries

• Compiles straight to Java byte code so you can use it anywhere you can use Java

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