Groovy & Grails: Scripting for Modern 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 usage

Agile Scaffolding Unit tests No build 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 Anonymous block of statements First class objects Parameters including default values Return value Binds variables in definition scope

Pluggable Behavior - Groovy def sum(num, closure) { def sum=0 1.upto(num) { if (closure(it)) sum+=it } } total=sum(10){it%2==0} println "Total: ${total}"

Pluggable Behavior - Java public static int sum(int num, Algo algo) { int val=0; for (int i=1; i<=n, i++) { if (algo.eval(i)) val+=i; } return val; } public static void main (String[] args) { int total; total = sum(10, new Algo() { public boolean eval(int i) { return i%2==0; } } }); System.out.println("Total: " + total); }

Dynamic Programming Add methods, properties to classes/objects at run-time Mixins to inject behaviour class ListUtils { static foo(List list) { "foo called" } } List.metaClass.mixin ListUtils assert "foo called" == [1, 2, 3].foo() Can extend class field-access mechanism Dynamic method invocation myObj.”$action”()

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 model class hasMany defines relationship & declares variable Layout, form validations Lightweight Modify and F5 Strong shoulders Spring (Grails MVC, DI, Transactions) Hibernate (GORM) Ant, JUnit, SiteMesh, log4j, OSCache

Grails – Key Features Database mapping, relations MySQL integration URL Mapping Authentication / Filters Logging

Grails Web Application Rest Service Proxy Custom Tag libraries Sitemesh layout Templates

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

Cons Learning curve Performance ?! Early adopter issues Dynamic/Functional programming

Scripted In Groovy Canoo WebTest Tellurium Ant / Maven config files SoapUI script step Spring beans

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[] var1 = 123; binding.setVariable("args",var1); String ret = gse.run(“DoSomething.groovy", binding); } }

Groovy Script Eval import javax.script.ScriptEngine; import javax.script.ScriptEngineManager; public class CalcMain { public static void main(String[] args) throws Exception { ScriptEngineManager factory = new ScriptEngineManager(); ScriptEngine engine = factory.getEngineByName("groovy"); // basic example System.out.println(engine.eval("(1..10).sum()")); //  55 // example showing scripting variables engine.put("first", "HELLO"); engine.put("second", "world"); System.out.println(engine.eval("first.toLowerCase() + second.toUpperCase()")); //  helloWORLD } }

Using Grails Web UI Flow Prototyping REST Service Prototyping Supporting Web Apps Internal Web Apps

Using Groovy Glue together existing components Reengineering legacy components Externalizing business logic, rules Domain Specific Languages Smart Configuration Scripting language of choice

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: Scripting for Modern Web Applications

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