What's New in Groovy 1.6?

What’s new in Groovy 1.6 Guillaume Laforge SpringSource Groovy Project Manager

Guillaume Laforge Groovy Project Manager — SpringSource

Working on Groovy since 2003

JSR-241 Spec Lead

Initiator of the Grails web framework

Co-author of Groovy in Action

Speaker: JavaOne, QCon, JavaPolis/Devoxx, JavaZone, Sun Tech Days, SpringOne/The Spring Experience, JAX, DSL DevCon, and more…

What’s new in Groovy 1.6? Article Published by InfoQ

This presentation was prepared with the examples I’ve used in my article written for InfoQ

http://www. infoq . com/articles/groovy-1-6

Read this article for more detailed explanations of all the new features in Groovy 1.6

Agenda

Groovy Overview

Performance Improvements

Syntax Enhancements

Compile-Time Metaprogramming

The Grape Module System

Swing-Related Improvements

Runtime Metaprogramming Additions

JSR-223 Scripting Engine Built-In

JMX Builder

OSGi Readiness

Groovy in a Nutshell Simplify the Life of Java Developers

Groovy is a dynamic language for the Java Virtual Machine

With a Meta-Object Protocol

Compiles down to bytecode

Open Source Apache licensed project

Relaxed grammar derived from the Java 5 grammar

Borrowed some good ideas from Smalltalk/Python/Ruby

Java 5 features out of the box: annotations , generics , static imports, enums…

Flat learning curve

Features at a Glance Lots More Than This!

Fully Object-Oriented

Joint compiler : seamless Java integration

Closures : reusable blocks of code / anon functions

Properties : forget about getters and setters

Optional typing: your choice!

BigDecimal arithmetic by default for floating point

Handy APIs

XML, JDBC, JMX, template engine, Swing UIs

Strong ability for authoring Domain-Specific Languages

Syntax-level “builders”

Adding properties to numbers: 10.dollars

Operator overloading: 10.meters + 20.kilometers

A Taste of Groovy — Take 1 A Normal Java Program

public class HelloWorld { private String name; public void setName(String name) { this.name = name; } public String getName() { return name; } public String greet() { return "Hello " + name; } public static void main(String[] args) { HelloWorld helloWorld = new HelloWorld(); helloWorld.setName("Groovy"); System.out.println( helloWorld.greet() ); } }

A Taste of Groovy — Take 2 A Valid Groovy Program

public class HelloWorld { private String name; public void setName(String name) { this.name = name; } public String getName() { return name; } public String greet() { return "Hello " + name; } public static void main(String[] args) { HelloWorld helloWorld = new HelloWorld(); helloWorld.setName("Groovy"); System.out.println( helloWorld.greet() ); } }

A Taste of Groovy — Take 3 A Groovier Program!

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

The Groovy Web Console A Groovy Playground

Groovy works nicely on Google App Engine

You can also deploy Grails applications

You can play with Groovy in the web console

http: //groovyconsole . appspot . com/

The Groovy Web Console A Screenshot

Agenda

Groovy Overview

Syntax Enhancements

JMX Builder

OSGi Readiness

Performance Improvements Both Runtime & Compile-Time

The Groovyc compiler is 3x to 5x faster

With a clever class lookup cache

Certain online micro-benchmarks show 150% to 460% increase in performance compared to Groovy 1.5

Thanks to advanced call-site caching techniques

Beware of micro-benchmarks!

Makes Groovy one of the fastest dynamic languages available

Agenda

Groovy Overview

Syntax Enhancements

JMX Builder

OSGi Readiness

Multiple Assignment Assign Multiple Variables at Once

Newly defined variables

def (a, b) = [1, 2] assert a == 1 assert b == 2

Assign to existing variables

def lat, lng (lat, lng) = geocode(‘Paris’)

The classical swap case

(a, b) = [b, a]

Extra elements  not assigned to any variable

Less elements  null into extra variables

More Optional Return In if/else and try/catch Blocks

The return keyword is optional for the last expression of a method body

But if / else & try / catch didn’t return any value

def method() { if (true) 1 else 0 } assert method() == 1

def method(bool) { try { if (bool) throw new Exception("foo") 1 } catch(e) { 2 } finally { 3 } } assert method(false) == 1 assert method(true) == 2

Annotation Definition The Missing Bit of Java 5 Support

Groovy support for Java 5 features is now complete with the missing annotation definition

Nothing to show here, it’s just normal Java :-)

Note that the sole dynamic language supporting annotation is… Groovy

Opens the door to EJB3 / JPA / Spring annotations / Guice / TestNG…

Agenda

Groovy Overview

Syntax Enhancements

JMX Builder

OSGi Readiness

Meta-What? Meta-Programming

The ability of a language to modify itself

Groovy 1.6 introduces AST Transformations

Abstract Syntax Tree

Goodbye to a lot of boiler-plate technical code!

Two kinds of transformations

Global transformations

Local transformations: triggered by annotations

AST Transformations in Groovy 1.6 Implement Patterns through Transformations

Several transformations finds their way

@Singleton — okay, not really a pattern ;-)

@Immutable , @Lazy , @Delegate

@Newify

@Category and @Mixin

@PackageScope

Swing’s @Bindable and @Vetoable

Grape’s @Grab

Let’s have a look at some of them!

@Singleton (Anti-)Pattern Revisited

The evil Java singleton

public class Evil { public static final Evil instance = new Evil (); private Evil () {} Evil getInstance() { return instance; } }

In Groovy:

@Singleton class Evil {}

There’s also a « lazy » version

@Singleton(lazy = true) class Evil {}

@Immutable The Immutable… Boiler-Plate Code

To properly implement immutable classes

No mutators (state musn’t change)

Private final fields

Defensive copying of mutable components

Proper equals() / hashCode() / toString() for comparisons or for keys in maps, etc.

In Groovy

@Immutable final class Coordinates { Double lat, lng } def c1 = new Coordinates(lat: 48.8, lng: 2.5) def c2 = new Coordinates(48.8, 2.5) assert c1 == c2

@Lazy Not Just for Lazy Dudes!

When you need to lazy evaluate / instantiate complex data structures for class fields, mark them as @Lazy

class Dude { @Lazy pets = retrieveFromSlowDB() }

Groovy will handle the boiler-plate code for you

@Delegate Not Just for Managers!

You can delegate to fields of your class

Think multiple inheritance

class Employee { def doTheWork() { "done" } } class Manager { @Delegate Employee slave = new Employee() } def god = new Manager() assert god.doTheWork() == "done"

Damn manager who will get all the praise…

Agenda

Groovy Overview

Syntax Enhancements

JMX Builder

OSGi Readiness

Grab a Grape Groovy Advanced Packaging Engine

Helps you distribute scripts without dependencies

Just declare your dependencies with @Grab

Will look for dependencies in Maven or Ivy repositories

@Grab(group = 'org.mortbay.jetty', module = 'jetty-embedded', version = '6.1.0') def startServer() { def srv = new Server(8080) def ctx = new Context(srv , "/", SESSIONS); ctx.resourceBase = "." ctx.addServlet(GroovyServlet, "*.groovy") srv.start() }

Agenda

Groovy Overview

Syntax Enhancements

JMX Builder

OSGi Readiness

@Bindable (1/2) Event-Driven Made Easy

Speaking of boiler-plate code… property change listeners

import java.beans.PropertyChangeSupport; import java.beans.PropertyChangeListener; public class MyBean { private String prop; PropertyChangeSupport pcs = new PropertyChangeSupport(this); public void addPropertyChangeListener(PropertyChangeListener l) { pcs.add(l); } public void removePropertyChangeListener(PropertyChangeListener l) { pcs.remove(l); }

public String getProp() {

return prop; }

public void setProp(String prop) { pcs.firePropertyChanged("prop", this.prop, this.prop = prop); } }

@Bindable (2/2) Event-Driven Made Easy

Groovy’s solution

class MyBean { @Bindable String prop }

Interesting in Griffon and Swing builder

textField text: bind { myBean.prop }

Also of interest: @Vetoable

Griffon The Swing MVC Framework

Leverages Groovy’s SwingBuilder and Grails’ infrastructure

http://griffon.codehaus.org

Don’t miss the “Griffon in Depth” BOF-5189!

Wednesday 8:45pm, Gateway 104

Swing Console Improvements

The console can be run as an applet

Code indentation support

Script drag’n drop

Add JARs in the classpath from the GUI

Execution results visualization plugin

Clickable stacktraces and error messages

Not intended to be a full-blown IDE, but handy

Agenda

Groovy Overview

Syntax Enhancements

JMX Builder

OSGi Readiness

ExpandoMetaClass DSL Less Repetition

EMC is a way to change the behavior of types at runtime

Before

Number.metaClass.multiply = { Amount amount -> amount.times(delegate) } Number.metaClass.div = { Amount amount -> amount.inverse().times(delegate) }

Now in Groovy 1.6

Number.metaClass { multiply { Amount amount -> amount.times(delegate) } div { Amount amount -> amount.inverse().times(delegate) } }

Runtime Mixins Inject New Behavior to Types at Runtime

class FlyingAbility { def fly() { "I'm ${name} and I fly!" } } class JamesBondVehicle { String getName() { "James Bond's vehicle" } } JamesBondVehicle.mixin FlyingAbility assert new JamesBondVehicle().fly() == "I'm James Bond's vehicle and I fly!"

Agenda