1. Guillaume Laforge / Groovy Project Manager / SpringSource
What’s new in Groovy 1.6?
All the novelties of the latest version!
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2. Guillaume Laforge
Groovy Project Manager — SpringSource
Working on Groovy since 2003
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> JSR-241 Spec Lead
Initiator of the Grails web framework
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Co-author of Groovy in Action
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Speaker: JavaOne, QCon, JavaPolis/Devoxx,
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JavaZone, Sun Tech Days, SpringOne/The Spring
Experience, JAX, DSL DevCon, and more…
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3. What’s new in Groovy 1.6?
Article Published by InfoQ
This presentation was prepared with the examples
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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
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5. Groovy in a Nutshell
Simplify the Life of Java Developers
Groovy is a dynamic language for the Java Virtual
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Machine
With a Meta-Object Protocol
Compiles down to bytecode
Open Source Apache licensed project
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> 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
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6. Features at a Glance
Fully Object-Oriented
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Joint compiler: seamless Java integration
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Closures: reusable blocks of code / anon functions
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Properties: forget about getters and setters
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Optional typing: your choice!
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BigDecimal arithmetic by default for floating point
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Handy APIs
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XML, JDBC, JMX, template engine, Swing UIs
Strong ability for authoring Domain-Specific Languages
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Syntax-level “builders”
Adding properties to numbers: 10.dollars
Operator overloading: 10.meters + 20.kilometers
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7. 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() );
}
}
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8. 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() );
}
}
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9. 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()
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10. The Groovy Web Console
A Groovy Playground
Groovy works nicely on Google App Engine
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You can also deploy Grails applications
You can play with Groovy in the web console
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http://groovyconsole.appspot.com/
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12. Performance Improvements
Both Runtime & Compile-Time
The Groovyc compiler is 3x to 5x faster
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With a clever class lookup cache
Certain online micro-benchmarks show
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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
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14. Multiple Assignment
Assign Multiple Variables at Once
Newly defined variables
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def (a, b) = [1, 2]
assert a == 1
assert b == 2
Assign to existing variables
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def lat, lng
(lat, lng) = geocode(‘Paris’)
The classical swap case
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(a, b) = [b, a]
Extra elements ⇒ not assigned to any variable
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> Less elements ⇒ null into extra variables
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15. More Optional Return
In if/else and try/catch Blocks
The return keyword is optional for the last expression
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of a method body
But if/else & try/catch didn’t return any value
def method() { if (true) 1 else 0 }
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assert method() == 1
def method(bool) {
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try {
if (bool) throw new Exception(quot;fooquot;)
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} catch(e) { 2 }
finally {3}
}
assert method(false) == 1
assert method(true) == 2
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16. Annotation Definition
The Missing Bit of Java 5 Support
Groovy support for Java 5 features is now complete
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with the missing annotation definition
Nothing to show here, it’s just normal Java :-)
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Note that the sole dynamic language
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supporting annotation is… Groovy
Opens the door to EJB3 / JPA / Spring annotations /
Guice / TestNG…
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18. Meta-What?
Meta-Programming
The ability of a language to modify itself
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Groovy 1.6 introduces AST Transformations
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Abstract Syntax Tree
Goodbye to a lot of boiler-plate technical code!
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Two kinds of transformations
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Global transformations
Local transformations: triggered by annotations
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19. AST Transformations in Groovy 1.6
Implement Patterns through Transformations
Several transformations finds their way
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@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!
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20. @Singleton
(Anti-)Pattern Revisited
The evil Java singleton
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public class Evil {
public static final Evil instance = new Evil ();
private Evil () {}
Evil getInstance() { return instance; }
}
In Groovy:
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@Singleton() class Evil {}
There’s also a « lazy » version
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@Singleton(lazy = true) class Evil {}
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21. @Immutable
The Immutable… Boiler-Plate Code
To properly implement immutable classes
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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
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@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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22. @Lazy
Not Just for Lazy Dudes!
When you need to lazy evaluate / instantiate
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complex data structures for class fields, mark them
as @Lazy
class Dude {
@Lazy pets = retriveFromSlowDB()
}
Groovy will handle the boiler-plate code for you
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23. @Delegate
Not Just for Managers!
You can delegate to fields of your class
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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…
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27. @Bindable (1/2)
Event-Driven Made Easy
Speaking of boiler-plate code… property change listeners
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import java.beans.PropertyChangeSupport;
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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);
}
}
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28. @Bindable (2/2)
Event-Driven Made Easy
Groovy’s solution
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class MyBean {
@Bindable String prop
}
Interesting in Griffon and Swing builder
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textField text: bind { myBean.prop }
Also of interest: @Vetoable
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29. Griffon
The Swing MVC Framework
Leverages Groovy’s SwingBuilder
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and Grails’ infrastructure
http://griffon.codehaus.org
Don’t miss the next session on!
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30. Swing Console Improvements
The console can be run as an applet
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> 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
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33. ExpandoMetaClass DSL
Less Repetition
EMC is a way to change the behavior of types at runtime
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Before
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Number.metaClass.multiply = { Amount amount ->
amount.times(delegate) }
Number.metaClass.div = { Amount amount ->
amount.inverse().times(delegate) }
Now in Groovy 1.6
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Number.metaClass {
multiply { Amount amount -> amount.times(delegate) }
div { Amount amount ->
amount.inverse().times(delegate) }
}
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34. Runtime Mixins
Inject New Behavior to Types at Runtime
class FlyingAbility {
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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;
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36. javax.script.* Scripting APIs
Groovy Scripting Engine Built-In
In Groovy 1.6, the JSR-223 / javax.script.* scripting
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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
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application, just drop the Groovy JAR in your
classpath!
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41. OSGi Readiness
The Groovy JAR contains OSGi metadata
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Can be reused in OSGi containers out-of-the-box
Tutorials on Groovy and OSGi
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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
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43. Summary
Just Remember that Groovy Rocks! :-)
Groovy 1.6 provides
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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
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