Whats New In Groovy 1.6?

What’s new in Groovy 1.6?

Guillaume Laforge
Groovy Project Manager / SpringSource

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…

2009 CommunityOne Conference: EAST | developers.sun.com/events/communityone 2
2

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

3

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

4

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

5

Features at a Glance
Lots More Than This!
> Fully Object-Oriented
> Joint compiler: seamless Java integration
> Closures: reusable blocks of code / anonymous 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

6

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 quot;Hello quot; + name;
}
public static void main(String[] args) {
HelloWorld helloWorld = new HelloWorld();
helloWorld.setName(quot;Groovyquot;);
System.out.println( helloWorld.greet() );
}
}

7

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 quot;Hello quot; + name;
}
public static void main(String[] args) {
HelloWorld helloWorld = new HelloWorld();
helloWorld.setName(quot;Groovyquot;);
System.out.println( helloWorld.greet() );
}
}

8

A Groovier Program!

> class HelloWorld {
String name
String greet() { quot;Hello $namequot; }
}
def helloWorld = new HelloWorld(name: quot;Groovyquot;)
println helloWorld.greet()

9

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/

10

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

11

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

12

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

13

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
14

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(quot;fooquot;)
1
} catch(e) { 2 }
finally { 3 }
}
assert method(false) == 1
assert method(true) == 2
15

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…

16

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

17

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

18

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!

19

@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 {}

20

@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
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@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 = retriveFromSlowDB()
}

> Groovy will handle the boiler-plate code for you

22

@Delegate
Not Just for Managers!

> You can delegate to fields of your class
 Think multiple inheritance
 class Employee {
def doTheWork() { quot;donequot; }
}
class Manager {
@Delegate
Employee slave = new Employee()
}
def god = new Manager()
assert god.doTheWork() == quot;donequot;

> Damn manager who will get all the praise…

23

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

24

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 , quot;/quot;, SESSIONS);
ctx.resourceBase = quot;.quot;
ctx.addServlet(GroovyServlet, quot;*.groovyquot;)
srv.start()
}

25

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

26

@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(quot;propquot;, this.prop, this.prop = prop);
}
}

27

@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

28

Griffon
The Swing MVC Framework

> Leverages Groovy’s SwingBuilder
and Grails’ infrastructure
 http://griffon.codehaus.org

> Don’t miss the Griffon BOF!

29

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

30

31

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

32

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) }
}

33

Runtime Mixins
Inject New Behavior to Types at Runtime

> class FlyingAbility {
def fly() { quot;I'm ${name} and I fly!quot; }
}

class JamesBondVehicle {
String getName() { quot;James Bond's vehiclequot; }
}

JamesBondVehicle.mixin FlyingAbility

assert new JamesBondVehicle().fly() ==
quot;I'm James Bond's vehicle and I fly!quot;

34

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

35

javax.script.* Scripting APIs
Groovy Scripting Engine Built-In
> In Groovy 1.6, the JSR-223 / javax.script.* scripting engine
for Groovy is bundled

 import javax.script.*
def manager = new ScriptEngineManager()
def engine =
manager.getEngineByName(quot;groovyquot;)
assert engine.evaluate(quot;2 + 3quot;) == 5

> To evaluate Groovy scripts at runtime in your application,
just drop the Groovy JAR in your classpath!

36

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

37

JMX Builder (1/2)
Domain-Specific Language for JMX
> Simplify JMX handling with a Builder pattern approach
> Declaratively expose Java/Groovy objects as MBeans
> JMX's event model support
 Inline closures to create event handler & broadcaster

 Closures for receiving event notifications

> Provides a flexible registration policy for MBean
> Exposes attribute, constructors, operations, parameters,
and notifications
> Simplified creation of connector servers & clients
> Support for exporting JMX timers

> http://groovy.codehaus.org/Groovy+JmxBuilder

38

JMX Builder (2/2)
Examples
> Create a connector server
 def jmx = new JmxBuilder()
jmx.connectorServer(port:9000).start()
> Create a connector client
 jmx.connectorClient(port:9000).connect()
> Export a bean
 jmx.export { bean new MyService() }
> Defining a timer
 jmx.timer(name: quot;jmx.builder:type=Timerquot;,
event: quot;heartbeatquot;, period: quot;1squot;).start()
> JMX listener
 jmx.listener(event: quot;…quot;, from: quot;fooquot;,
call: { event -> …})

39

Agenda
> Groovy Overview
> JMX Builder
> OSGi Readiness

40

OSGi Readiness

> The Groovy JAR contains OSGi metadata
 Can be reused in OSGi containers out-of-the-box

> Tutorials on Groovy and OSGi
 http://groovy.codehaus.org/OSGi+and+Groovy
 Will show you how to load Groovy as a service, write, publish and
consume Groovy services, and more

41

Summary
Just Remember that Groovy Rocks! :-)
> Groovy 1.6 provides
 Important performance gains
 Efficient compile-time metaprogramming hooks
 New useful features (JMX, javax.script.*, etc.)
 A script dependencies system
 Various Swing-related improvements
 Several runtime metaprogramming additions

> Get it now!
 http://groovy.codehaus.org/Download

43


Guillaume Laforge
glaforge@gmail.com

Whats New In Groovy 1.6?

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