The document discusses next-generation programming languages that run on the Java Virtual Machine (JVM), focusing on Groovy and the Grails web application framework. It provides an overview of Groovy's features like closures and first-class containers. It also demonstrates building a sample web application in Groovy/Grails and discusses how Groovy integrates seamlessly with Java.

1. Cool Web Apps with Grails, Groovy and Next-Gen Scripting Languages William Grosso Twofish

6. Who Am I?

9. Up and running for >3 months without any attention from me

17. But I Wasn’t Completely Right JVM Platform Libraries and Application Frameworks Your App / Your Web App Your Libraries Your Prototypes Down here, Java, super clear semantics, WORA etcetera win Hmm. Community properties probably only matter for largish things that you share or keep and reuse for a long time. Maybe we can do better than Java?

18. Lots of people having similar thoughts. The JVM is robust enough, and the platform is robust enough, and … that people are starting to seriously layer languages on top.

19. Short list of “interesting” languages: Jython JRuby Scala Groovy Kawa Clojure PHP NetRexx (??)

20. Completely a sidenote: If you’re curious about programming language design, this is the single best site on the web

21. Closures have been THE hot topic in commercial language design

22. Odersky’s claim: closures + first class containers + super strong typing are the bees knees

23. Complexity is bad. Java is near the edge of the cliff. 4.5M PDF and a Tiny Thumbnail? For Generics? Ruby has a similar problem (more later)

24. Desiderata for the Tiers JVM Platform Libraries and Application Frameworks Your App Your Libraries Your Prototypes Strong typing Absolutely clear semantics Minimal evolution of language None of the other stuff is necessary Looks like Java Clear, readable code Non-verbose language Complete integration with Java First class containers Closures Great XML support Rapid Prototyping (REPL) Metaobject Protocol

27. Looks Like Java Go read the code examples It’s easy

28. Let’s Look at Concurrency Not Java def? 1 .. 8 sleep 30 But … it’s close

30. import groovy.swing.*; import java.awt.*; import javax.swing.*; class Model extends Observable { static CURRENCY = ["USD", "EURO", "YEN"] private Map rates = new HashMap() private long value void initialize(initialRates) { (0..CURRENCY.size() - 1).each { setRate(CURRENCY[it], initialRates[it]) } } // setting rate for currency void setRate(currency, f) { rates.put(currency, f); setChanged(); notifyObservers(currency); } // setting new value for currency void setValue(currency, double newValue) { value = Math.round(newValue / rates[currency]); setChanged(); notifyObservers(null); } // getter for value for particular currency def getValue(currency) { value * rates[currency] } } class RateView extends JTextField implements Observer { private Model model; private currency; public void setModel(Model model) { this.model?.removeObserver(this) this.model = model model.addObserver(this) } public void update(Observable o, Object currency) { if (this.currency == currency) text = String.format("%15.2f", model.rates[currency]) } } class ValueView extends JTextField implements Observer { private Model model private currency public void setModel(Model model) { this.model?.removeObserver(this) this.model = model model.addObserver(this) } public void update(Observable o, Object currency) { if (currency == null || this.currency == currency) text = String.format("%15.2f", model.getValue(this.currency)); } }

31. swing = new SwingBuilder() model = new Model() frame = swing.frame(title: "Groovy SwingBuilder MVC Demo", layout: new GridLayout(4, 3), size: [300, 150], defaultCloseOperation: WindowConstants.EXIT_ON_CLOSE) { label("currency") label("rate") label("value") for (c in Model.CURRENCY) { label(c) widget(new RateView(), model: model, currency: c, action: swing.action(closure: { event -> event.source.model.setRate(event.source.currency, event.source.text.toDouble()); })) widget(new ValueView(), model: model, currency: c, action: swing.action(closure: {event -> event.source.model.setValue(event.source.currency, event.source.text.toDouble()); })) } } frame.show() model.initialize([1.0, 0.83, 0.56]);

35. weekMap = [ "Su" : "Sunday", "Mo" : "Monday", "Tu" : "Tuesday", "We" : "Wednesday", "Th" : "Thursday", "Fr" : "Friday", "Sa" : "Saturday" ] weekMap.each() { key, value -> println "${key} == ${value}" }

39. Don’t believe me? Neal likes Java a LOT more than I do

45. Chris will talk more about GORM later on

47. What’s Martin Fowler been doing since the refactoring book anyway?

50. MarkupBuilder import groovy.xml.MarkupBuilder def writer = new StringWriter() def xml = new MarkupBuilder(writer) xml.records() { car(name:'HSV Maloo', make:'Holden', year:2006) { country('Australia') record(type:'speed', 'Production Pickup Truck with speed of 271kph') } car(name:'P50', make:'Peel', year:1962) { country('Isle of Man') record(type:'size', 'Smallest Street-Legal Car at 99cm wide and 59 kg in weight') } car(name:'Royale', make:'Bugatti', year:1931) { country('France') record(type:'price', 'Most Valuable Car at $15 million') } } println writer.toString()

53. The Rails guys invented the “movie to demo the framework” idea and their movies are still WOW OH WOW GOOD

55. In 4 years, Rails has made very impressive strides. Market leader in the “early stage startup” category.

57. Backwards compatibility is not a huge priority

58. Backwards compatibility is not a huge priority

59. This is scary

60. Of course, Java is mostly developed by Sun ….

61. This is from a Ruby guy who doesn’t like JRuby very much …

67. SWAG Estimate: About ¾ of plugins are mentioned here (BIRT, for example, is not)

70. <<IntelliJ>>

75. Additional Reading

76. This is a great series of articles. Whenever anyone tells you a technology is going to be big, ask yourself: WWTT?