Download - Wicket and Scala

Daan van Ettenhttp://stuq.nl

Amsterdam, March 24, 2009

Basic Wicket and Scala

Goal:

After this talk, you can start coding Wicket in Scala.

Overview

ScalaWhat is

?

Hello, World!

Functional concepts

Simple project

Java Scala

Who am I?

Daan van Etten

Daan van Etten

Software Engineer

Software Engineer

Daan van Etten

@work

Software Engineer

Daan van Etten

Let’s begin

ScalaWhat is

?

Scala

History

Scala

1958

Scala

Martin Odersky

Scala

Compilers

Scala

Functional languages

(more about that later)

Scala

GenericJava

Scala

Java 5Generics

Scala

New javac

Scala

2001

Scala

Scala

Scala

First release

Scala

2003

Scala

Object Oriented

Scala

Functional

Scala

Statically typed

Scala

Type inference

var foo = 8foo = “bar”

type mismatch;found: String("bar")required: Int

Scala

Every value is an object

var foo = 8def bar(a: String)= println(a)

1 + 3 - 61.+(3).-(6)

Scala

Every operation is a method call

Scala

Compiles toJava bytecode

Scala

Runs on theJava VM

Scala

ScalableFrom small scripts to large systems

Scala

Hello, World!

Scala

object HelloWorld { def main(args: Array[String]) { println("Hello, world!") } }

Scala

20 seconds

Scala

Functional concepts

ScalaDesign goals:

Embrace immutabilityAvoid state

Scala

Cleaner code

More !ne-grained reuseNo Iterator loops needed :-)

Scala

Better optimizationsMulti-core!

Lazy evaluationRecursion

Scala

What aboutthe functions?

1 + 3 - 61.+(3).-(6)

Scala

Every operation is a method call

Scala

def function1(x : Int) = { def function2() = { println(x) } function2()}

Function nesting

Scala

def foo (cb: ()=>Unit): Unit = { while (true) { cb(); Thread.sleep(1000); }}

foo(Unit : println("hi"))

First-class functions

First-class functions in libraries

Scala

val numbers = List(2,5,8,9)numbers.foreach( (x: Int) => print(x) )

Anonymous functions

Scala

((i:Int, j:Int) => i + j)(3, 4)

Java:int calc(int i, int j){ return i + j; }; calc(3, 4);

Scala

Partially applied functions

def calc(x:Int, y:Int, z:Int)=x+y+z

val calcPart = calc(1, _:Int, 3)

calcPart(4)

Simple project

+

+

Hello, Wicket World!

object HelloWorld { def main(args: Array[String]) { println("Hello, world!") } }

+

class HelloWorld extends WebApplication { def main(args: Array[String]) { println("Hello, world!") } }

+

class HelloWorld extends WebApplication {

}

+

class HelloWorld extends WebApplication { def getHomePage = classOf[HomePage]}

+

class HelloWorld extends WebApplication { def getHomePage = classOf[HomePage]}class HomePage extends WebPage {

}

+

class HelloWorld extends WebApplication { def getHomePage = classOf[HomePage]}class HomePage extends WebPage {

}

+

var name = "" val form = new Form("form") add(form) form.add(new TextField("name", new PropertyModel(this, "name"))) form.add(new Label("helloworld", new PropertyModel(this, "name")))

<body> <p><b>Hello, Wicket World!</b></p> <form wicket:id="form"> What's your name? <br/> <input wicket:id="name"/> <input type="submit" value = "OK" />

<p>Your name is: <b><span wicket:id="helloworld"/></b> </p> </form></body>

+

EASYREUSABLE

NON-INTRUSIVESAFE

EFFICIENT SCALABLE

EASYPOJO-centric

EASYAll code in Java

EASYAll code in Java

or Scala

EASYMaximum type safety and

compile-time problem diagnosis

EASYMinimum reliance on

special tools

REUSABLE

REUSABLE

Function reuse

REUSABLE

NON-INTRUSIVE

HTML or other markupnot polluted with

programming semantics

NON-INTRUSIVE

But... Scala != Java

NON-INTRUSIVE

NON-INTRUSIVE

?

Code is secure by default

SAFE

SAFEAll logic in Java (or Scala)

with maximum type safety

EFFICIENT / SCALABLE

E!cient and lightweight


Scala means reducingthe amount of code.


EASYREUSABLE

NON-INTRUSIVESAFE

EFFICIENT SCALABLE

maven-scala-plugin

maven

mavenUnder <build> <plugins><plugin> <groupId>org.scala-tools</groupId> <artifactId>maven-scala-plugin</artifactId> <executions> <execution> <goals> <goal>compile</goal> <goal>testCompile</goal> </goals> </execution> </executions></plugin>

mavenUnder <pluginRepositories>

<pluginRepository> <id>scala</id> <name>Scala Tools</name> <url>http://scala-tools.org/repo-releases</url> <releases> <enabled>true</enabled> </releases> <snapshots> <enabled>false</enabled> </snapshots></pluginRepository>

mavenUnder <repositories>

<repository> <id>scala</id> <name>Scala Tools</name> <url>http://scala-tools.org/repo-releases</url> <releases> <enabled>true</enabled> </releases> <snapshots> <enabled>false</enabled> </snapshots></repository>

mavenUnder <dependencies>

<dependency> <groupId>org.scala-lang</groupId> <artifactId>scala-library</artifactId> <version>2.7.3</version></dependency>

maven

You can add this to anyJava+Maven project!

maven

Project layout

maven

src

pom.xml

main

java

test

java

maven

src

pom.xml

main

scala

test

scala

maven

src

pom.xml

main

java

test

java

scala

scala

maven

Hello, Wicket World!built in Maven

Download thedemo project.

Java Scala

Java Scala

Java interfaceimplemented in Scala

Java Scala

public interface SomeInterface { void doSomething(String argument);}

class SomeImplementation extends SomeInterface { def doSomething(argument: String):Unit = { println(argument) }}


Java Scala


class SomeImplementation extends SomeInterface { def doSomething(argument: String):unit = { println(argument) }}

?

Java Scala

Scala does not have interfaces!

Java Scala

Scala has traits

Java Scala

class SomeImplementation extends SomeInterface { def doSomething(argument: String) : unit = { println(argument) }}

extending a trait

Java Scala

interface != trait

Java Scala

traits can havemethod

implementations

Java Scala


trait SomeTrait { def doSomething=(argument:String):Unit}

Java Scala


trait SomeTrait { def doSomething(argument:String):Unit def computeSomething = title.length * 10}

Java Scala


class SomeImplementation extends SomeInterface { def doSomething(argument: String):Unit = { println(argument) }}

Java Scala


class SomeImplementation extends SomeInterface {

}

Java Scala

Error: class SomeImplementation needs to be abstract, since method doSomething in trait SomeInterface of type (java.lang.String)Unit is not defined.

Java Scala

Java and Scala combined:Circular dependencies

class SomeImplementation extends SomeInterface { def doSomething=(argument:String):Unit {...}}


Java Scala

public class Other extends SomeImplementation { ...}

Handles circular

dependencies!

Java Scala

maven-scala-plugin

Java Scala

How?

Java Scala

scalac

parses Java code(since 2.7.2)

class SomeImplementation extends SomeInterface { def doSomething=(argument:String):Unit {...}}


Java Scala

public class Other extends SomeImplementation { ...}

Scala home on the web.

Reference manuals, tutorials,news, speci!cations.

http://www.scala-lang.org

http://www.scala-lang.org/

http://www.scala-lang.org/

Interpreter, variables, methods, loops, arrays, lists, tuples, sets, maps, classes,

singletons, traits, mixins.

http://www.artima.com/scalazine/articles/steps.html



Multiple articles covering afeature by feature comparison

of Scala and Java

http://blogs.sun.com/sundararajan/entry/scala_for_java_programmers



Series of 6 great articlescovering a lot of Scala.

Aimed at Java developers.

http://www.codecommit.com/blog/scala/roundup-scala-for-java-refugees



Scala Wiki.

FAQ, code samples, design patterns, Scala job openings

http://scala.sygneca.com/



O"cial mailing lists

Subscribe: empty message [email protected]#.ch

http://www.scala-lang.org/node/199


mailto:[email protected]

mailto:[email protected]


All samples can be downloaded at

http://stuq.nl

http://stuq.nl

http://stuq.nl

Get started with Scala and Wicket!

Thanks!

Download - Wicket and Scala

Top Related