GR8Conf 2009: What's New in Groovy 1.6? by Guillaume Laforge

What’s new in Groovy 1.6? Get started with Groovy and learn about all the novelties in the latest release Guillaume Laforge Head of Groovy Development

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… 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 4

nda Ag e > 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 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 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 "Hello " + name; } public static void main(String[] args) { HelloWorld helloWorld = new HelloWorld(); helloWorld.setName("Groovy"); System.out.println( helloWorld.greet() ); } } 7

A Taste of Groovy — Take 2 A Normal 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() ); } } 8

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() 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

The Groovy Web Console A Screenshot 11

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 12

Joint Compilation • Total Java interoperability • Concretely, what does it mean? JInterface GInterface <<implements>> <<implements>> GClass JClass JClass GClass 13

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+/) { ... } 14

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! ””” 15

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) 16

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) 17

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!” } } } } 18

Parsing XML • And it’s so easy to parser XML and navigate through the node graph! • def geocodingUrl = "http://...".toURL() geocodingUrl.withInputStream { stream -> def node = new XmlSlurper().parse(stream) if (node.Response.Status.code == "200") { def text = node.Response.Placemark. Point.coordinates.text() def coord = text.tokenize(','). collect{ Float.parseFloat(it) } (latitude, longitude) = coord[1..0] } } 19

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 21

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 23

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 24

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… 25

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 27

AST Transformations in 1.6 Implement Patterns through Transformations > Several transformations find their way in Groovy 1.6  @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! 28

@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 {} 29

@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 30

@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 31

@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… 32

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() } 34

@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); } } 36

@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 37

Griffon The Swing MVC Framework > Leverages Groovy’s SwingBuilder and Grails’ infrastructure  http://griffon.codehaus.org 38

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 39

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) } } 42

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!" 43

javax.script.* Scripting APIs Groovy Scripting Engine Built-In > The JSR-223 / javax.script.* scripting engine for Groovy is bundled in Groovy 1.6  import javax.script.* def manager = new ScriptEngineManager() def engine = manager.getEngineByName("groovy") assert engine.evaluate("2 + 3") == 5 > To evaluate Groovy scripts at runtime in your application, just drop the Groovy JAR in your classpath! 45

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 47

JMX Builder (2/2) Domain-Specific Language for JMX > 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: "jmx.builder:type=Timer", event: "heartbeat", period: "1s").start() > JMX listener  jmx.listener(event: "…", from: "foo", call: { event -> …}) 48

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 50

Summary

Summary Just Remember that Groovy Rocks! :-) > Any Java developer is a Groovy developer! > Great for your next-generation general purpose programming language, as well as 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 52

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GR8Conf 2009: What's New in Groovy 1.6? by Guillaume Laforge

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GR8Conf 2009: What’s New in Groovy 1.6? by Guillaume Laforge — Presentation Transcript