Groovy and Grails talk

Groovy and Grails Prabhu prabhu@prabhu-s.com

Groovy • is an agile and dynamic language for JVM • Features inspired from Python, Ruby … • Seamless integration with all existing Java classes and libraries. • Groovysh and GroovyConsole • Can run on .Net 2.0 using IKVM • Latest version 1.5 • http://groovy.codehaus.org

Features • Closures • Dynamic Methods • List & Maps • Better XML/Swing Capabilities

Closure • Statements enclosed within curly braces “{}“ • Can be passed around like variables • Return value either using return keyword or the value of last executed statement.

Closure (Contd) square = { it * it } square (4) Output = 16 “it” implicit parameter representing the passed value.

Closure (Contd) square { it * it return 3 } square (4) Output = 3 (Since there is an explicit return statement!)

Closure (Contd) square = { param1 -> param1 * param1 } square (3) Output = 9 Param1 – Named parameter

Factorial using closures fact = 1 fact = 1 for (i in 2..5) { (2..5).each { number -> fact *= i fact *= number } } print fact print fact // (2..5) = Range

Factorial again! fact = 1 2.upto(5) { num -> fact *= num } print fact // Numbers are treated as object. • upto method generates all number objects • To each object, the closure gets passed around!

Generic Factorial fact = 1 fun = { n-> 2.upto(n) { num -> fact *= num } } fun(5) print fact

Dynamic methods class webcamp { def haveTea() { println quot;Time for teaquot; } } camp = new webcamp() camp.haveTea()

Dynamic methods (Contd) • Add a new method “haveSamosa” class webcamp { def haveTea() { println quot;Time for tea“ } } camp = new webcamp() camp.haveTea() webcamp.metaClass.haveSamosa = { -> println quot;Have Samosa alsoquot; } camp = new webcamp() // Create a fresh object since the class has changed! camp.haveSamosa()

Lists and Maps • Like python List = [2,3,4] Map = [„a‟ : 2, „b‟ : new Date()]

Grails • Web Framework inspired by RoR • Latest version is 1.0.1. – The one in the DVD is 1.0 and doesn‟t run cleanly in windows! • Grails = Spring MVC 2.5.1 + Hibernate 3 + SiteMesh 2.3 • Newbie‟s are unaware that Grails is full and full Spring! • Provides several commands to auto generate code. • Comes bundled with HSQLDB.

Create your first app • Set environmental variables GRAILS_HOME and PATH • grails create-app firstapp

Directory Structure Controllers Domain Views Sources Test cases J2EE Web Appln.

First app Demo • grails create-domain-class <name> • grails create-controller <name> • grails run-app (Starts inbuilt Jetty 6.1.4 server) • Visit http://localhost:8080/firstapp • Demo

Features • Both gsp and jsp are supported. • Specify constraints static constraints = { username (minLength : 3, maxLength: 8, blank:false) password(minLength : 5, maxLength:9, blank:false) } • Specify Optional fields static optionals = [“middle_name”, “addr2”]

Features (Contd) • Dynamic finder methods def search = { render(view : „list‟, model : [userList : User.findAllByUsernameLike ( „%‟ + params.username + „%‟) ] ) } • User.findAllByUsernameLikeAndPassword Like

Features (Contd) • Create Advanced Search criteria using Hibernate Criteria Builder. def criteria = User.createCriteria() // Dynamic method def results = criteria { and ( like („username‟ , „%‟ + params.username + „%‟) le(„age‟, params.age) ) } Render(view:‟list‟, model:[userList : results])

Features (Contd) • Flash scope - Data will be stored as name-value pairs for current request and the next request. • Create custom tags just by creating a new file in grails- app/taglib/<name>TagLib.groovy

Features (Contd) • AJAX Support – Supports prototype, YUI, DOJO – Use render method in your groovy code to render text, HTML, JSON or OpenRico Response XMLs • Plays nicely with flex – Simply add this static expose = [“flex-remoting”] – Automatic flex based CRUD generation and Domain class to AS3 compilation coming up!

Features (Contd) • Plays nicely with EJB – http://www.infoq.com/articles/grails-ejb- tutorial • Has lots of plugins already! – grails install-plugin <name> – grails create-plugin <name>

Scalability • Thanks to Spring and Hibernate, Grails is highly scalable and already enterprise ready!

RoR Competition? • No. – Instead going to compete with Java based frameworks like struts 2, JSF, Seam.

Should I learn? • If you are a Java guy, then yes. • Companies like Oracle have already started showing full support!

Thanks Q&A

Groovy and Grails talk

by desistartups on Feb 23, 2008

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