1. An Introduction to Groovy
and the New Features in 1.6
Get started with Groovy and learn about
all the novelties in the latest release
Guillaume Laforge
Head of Groovy Development
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2. 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…
2
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3. 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
3
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4. 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
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5. Groovy in a Nutshell
Simplify the Life of Java Developers
Groovy is a dynamic language for the JVM
>
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
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6. • Are you a Groovy developer?
6
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7. • Ok, so, are you a Java developer?
7
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8. • Then, yes, you are a Groovy developer!
•Any Java developer is a
also a Groovy developer!
8
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9. 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() );
}
}
9
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10. 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 quot;Hello quot; + name;
}
public static void main(String[] args) {
HelloWorld helloWorld = new HelloWorld();
helloWorld.setName(quot;Groovyquot;);
System.out.println( helloWorld.greet() );
}
}
10
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11. A Taste of Groovy — Take 3
A Groovier Program!
class HelloWorld {
>
String name
String greet() { quot;Hello $namequot; }
}
def helloWorld = new HelloWorld(name: quot;Groovyquot;)
println helloWorld.greet()
11
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12. The Groovy Web Console
A Groovy Playground
Groovy works nicely on Google App Engine
>
You can also deploy Grails applications

You can play with Groovy in the web console
>
http://groovyconsole.appspot.com/

12
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13. The Groovy Web Console
A Screenshot
13
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14. Features at a Glance
Fully Object-Oriented
>
Joint compiler: seamless Java integration
>
Closures: reusable blocks of code / anon functions
>
Properties: forget about getters and setters
>
Optional typing: your choice!
>
BigDecimal arithmetic by default for floating point
>
Handy APIs
>
 XML, JDBC, JMX, template engine, Swing UIs
Strong ability for authoring Domain-Specific
>
Languages
 Syntax-level “builders”
 Adding properties to numbers: 10.dollars
 Operator overloading: 10.meters + 20.kilometers
14
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15. Joint Compilation
• Total Java interoperability
• Concretely, what does it mean?
JInterface GInterface
<<implements>>
<<implements>>
JClass
GClass
GClass
JClass
15
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16. Native Syntax Constructs
• Lists
– def numbers = [1, 2, 3, 4, 5]
• Maps
– def map = [FR: ‘France’, BE: ‘Belgium’]
• Ranges
– def allowed = 18..65
• Regular expressions
– def whitespace = ~/s+?/
– if (‘foo’ ==~ /o+/) { ... }
16
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17. GStrings!
• GStrings are... interpolated strings
– Sorry, not really what you expected!
– Placeholder variables are replaced
– You can have multiline strings
• def person = ‘John’
def letter = “““${new Date()}
Dear ${person},
I hope you’re fine!
”””
17
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18. Closures
• Closures are reusable and assignable code blocks or
anonymous functions
– No need to wait for Java 7/8/9 to get them!
– def greet = { println “Hello ${it}” }
greet(“Guillaume”)
• You can pass parameters
– def greet = { String name ->
println “Hello ${name}”
}
• You can passe closures around
– def method(Closure c) { c(“Hello”) }
method(greet)
18
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19. BigDecimal Arithmetic
• Main reason why financial institutions often decide
to use Groovy for their business rules!
– Although these days rounding issues are overrated!
• Java vs Groovy for a simple interpolation equation
• BigDecimal uMinusv = c.subtract(a);
BigDecimal vMinusl = b.subtract(c);
BigDecimal uMinusl = a.subtract(b);
return e.multiply(uMinusv)
.add(d.multiply(vMinusl))
.divide(uMinusl, 10, BigDecimal.ROUND_HALF_UP);
• (d * (b - c) + e * (c - a)) / (a - b)
19
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20. Groovy Builders
• The Markup builder
– Easy way for creating XML or HTML content
– def mkp = new MarkupBuilder()
mkp.html {
head {
title “Groovy in Action”
}
body {
div(width: ‘100’) {
p(class: ‘para’) {
span “Best book ever!”
}
}
}
}
20
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21. Parsing XML
• And it’s so easy to parser XML and navigate through
the node graph!
• def geocodingUrl = quot;http://...quot;.toURL()
geocodingUrl.withInputStream { stream ->
def node = new XmlSlurper().parse(stream)
if (node.Response.Status.code == quot;200quot;) {
def text = node.Response.Placemark.
Point.coordinates.text()
def coord = text.tokenize(',').
collect{ Float.parseFloat(it) }
(latitude, longitude) = coord[1..0]
}
}
21
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22. 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
>
22
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23. 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
23
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24. 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
>
24
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25. 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
>
25
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26. 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
26
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27. 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…
27
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28. 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
>
28
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29. 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

29
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30. 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!
>
30
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31. @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 {}

31
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32. @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
32
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33. @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
>
33
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34. @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…
>
34
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

35. 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
>
35
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

36. 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()
}
36
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

37. 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
>
37
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

38. @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);
}
}
38
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39. @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
>
39
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40. Griffon
The Swing MVC Framework
Leverages Groovy’s SwingBuilder
>
and Grails’ infrastructure
http://griffon.codehaus.org

40
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41. 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
>
41
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42. 42
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43. 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
>
43
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44. 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) }
}
44
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45. 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;
45
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

46. 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
>
46
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

47. 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!
47
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

48. 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
>
48
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

49. 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
49
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

50. 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 -> …})
50
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51. 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
>
51
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

52. 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
52
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53. Summary
Copyright 2009 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

54. Summary
Just Remember that Groovy Rocks! :-)
Any Java developer is a Groovy developer!
>
Great for admin tasks, extending apps, writing DSLs
>
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

54
Copyright 2008 SpringSource. Copying, publishing or distributing without express written permission is prohibited.

55. GR8 Conference
• If you wish to learn more about
Groovy, Grails and Griffon, register
for the GR8 Conference
• A conference dedicated to Groovy,
Grails, Griffon and other Groovy
related technologies
• Co-organized by SpringSource and the
Danish JUG (Javagruppen)
• Takes place in Copenhagen,
Denmark, on May 18th and 19th
• Use the code SPRING to get a
discount ;-)
55
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56. Questions & Answers
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