Groovy - Grails as a modern scripting language for Web applications

Groovy & Grails
Scripting for Modern Web Applications

Rohit Nayak
Talentica Software

Agenda

Demo: Quick intro to Grails

Scripting, Web Applications and Grails/Groovy

REST service in Grails
− Demo
− Internals

Web Client in Grails
− Demo
− Internals

Perspective

Maggi

grails create-app Maggi

Domain class: Noodle, Packaging

grails generate-all Noodle, Packaging

grails run-app

Web Frameworks with Scripting

Ruby on Rails (2004)


CakePHP (2005)


Django / Python (2005)


Groovy on Grails (2006)

Power of these frameworks

Baked Experience


The Language


Agility / Productivity

Baked Experience

Model View Controller

Object-Relational Mapping

Templates

Layout

URL rewriting

Ajax support

XML / JSON support

The Language

Dynamic

More expressive code

Smaller code

Native support for Lists, Hashmaps

Lang. support for IO, Net, XML

Idioms for common Design Patterns

Agile

Scaffolding

Unit tests

No compile cycles

Built-in webservers

Fail faster!

http://www.zacker.org/ruby-on-rails (Nov 2nd)

HelloWorld.java
public class HelloWorld {
String name;
public void setName(String name)
{ this.name = name; }
public String getName() { return name; }
public String hello()
{ return “Hello “+ name; }
public static void main(String args[]) {
HelloWorld helloWorld = new HelloWorld();
helloWorld.setName(“Java”);
System.out.println( helloWorld. hello() );
}
}

HelloWorld.groovy
class HelloWorld {
String name
def hello() { "Hello $name" }
}
def helloWorld = new HelloWorld(name:"Groovy")
println helloWorld.hello()

Key Groovy Features

Java-like syntax

Complements Java

Object-oriented

Targets Java VM (JSR-241)
− Invoke Java class within Groovy
− Invoke Groovy class within Java

Dynamic

Scripting (JSR-223)

Brevity

Brevity

Optional semicolons, package prefixes

Automatic imports (java.util.*, java.net.*,
java.io.*, groovy…)

GroovyBeans (generated accessors)

Optional typing

Optional return

Groovy Gravy

GStrings: ”$book.title: $book.author (${book.reviewers.length})”

Regular expressions: assert ‘12345’ =~ /d+/

Only objects: primitives converted to Reference Types

Lists: def list = [1, 2, 'hello', new java.util.Date()]

Maps: def map = ['name':‘Indic Threads', 'location':‘Pune']

Closures [1,2,3].collect {it*2} ===> [2, 4, 6]

String literals – single, double, triple quotes

Closures

Block of statements

First class objects

Parameters including default values

Carries local context
def foo(n) { // method
return { n += it } // returns closure
}
def accumulator = foo(1) //curried closure
assert accumulator(2) == 3 //assert used for self-documenting, unit-testing
assert accumulator(1) == 4

Dynamic Programming

Add methods, properties to classes/objects
at run-time

Mixins to inject behaviour

Can extend class field-access mechanism

Dynamic method invocation

Poolster

Online “football pools” application

Entities: Game, User

Game  Stake, Option, Ends

To join User chooses an Option

REST Webservice backend

Clients: iPhone, Grails, Android, Silverlight

Grails – Philosophy

Convention over Configuration
− Magic directories
− Implicit table names, column names

Don’t Repeat Yourself
− Database maps to domain
− hasMany defines relationship & declares variable
− Layout, form validations

Lightweight
− Modify and F5

Strong shoulders
− Spring (Grails MVC, DI, Transactions)
− Hibernate (GORM)
− Ant, JUnit, SiteMesh

Grails – Key Features

Database constraints, composition

MySQL integration

URL Mapping

Authentication / Filters

Bootstrapping

Unit test

Logging

Grails Web Application

Custom Tag libraries

Session variables

Sitemesh layout

Templates

Internationalization

Unseen Gravy

JUnit test cases, Mocking/Stubbing

Web testing with Canoo Webtest

Bootstrapping

Pagination

Cons

Learning curve

Performance ?!

Early adopter issues

Scripted In Groovy

Canoo WebTest

Tellurium

Ant / Maven config files

SoapUI script step

Spring beans

<YOUR APP HERE> 

Invoking Groovy Scripts
import java.io.File;
import groovy.lang.Binding;
import groovy.util.GroovyScriptEngine;

public class ScriptEngineEmbedGroovy{
public static void main(String args[]) throws Throwable{
String[] paths = {"C:groovy"};
GroovyScriptEngine gse = new GroovyScriptEngine(paths);
Binding binding = new Binding();
Object[] path = {"C:musicmp3"};
binding.setVariable("args",path);
gse.run("Songs.groovy", binding);
}
}

Getting Started

groovy.codehaus.org

grails.org

Free e-books
− Beginning Groovy and Grails (Apress)
− Getting started with Grails (InfoQ)

refcardz.com cheat sheets

ibm.com Mastering Grails, Practically Groovy

Groovy - Grails as a modern scripting language for Web applications

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