Introduction to Grails

James Williams

Introduction

James Williams

Groovy committer

Author of Google charts plugin

Griffon co-creator

Creator of SwingXBuilder

Agenda

What is Grails?

Domain Classes

Controllers

GSP/Taglibs

Plugins

Web Services

Conclusion

What is Grails?

Rapid web application development

Full-stack MVC framework

Open source

Runs on the JVM

What is Grails? (cont'd)

Integrates best of breed tools...

And many more...

Grails Quickstart

Install Grails

Run grails create-app

Run grails run-app

Domain Classes

Core objects that make up a Grails app

Are seamlessly persisted to storage

Can have constraints on values

Can have relationships with other domain classes

Constraints

Determine the validity of member fields

blank

creditCard

email

inList

matches

max

maxSize

min

minSize

notEqual

nullable

range

scale

size

unique

url

validator

Grails ORM (GORM)

No hassle database persistence

Leverages Hibernate but minus .hbm files and other messy configuration files

Provides dynamic domain class methods like...

create

save

delete

update

get

find

findAll

addTo

count

....

Relationships

One to one

One to many (hasMany)

Many to many

Demo

Domain Classes Demo

Controllers

Manages requests and response for domain objects

Unless overridden, maps requests to a REST-like structure
//action_name

It's actions can be generated on the fly by the application

Groovy Server Pages

Provide views for domain objects

Like JSP, GSPs can be a mix of markup, Groovy code and GSP tags*

Generally correspond to an associated action in the controller

Code fragments use the and forms, though this is discouraged

Typical GSP

%>

Taglibs

Allow the developer to simplify blocks of code

Similar to JSP tag libs
class SimpleTagLib {
def emoticon = { attrs, body
out