INTRODUCTIE IN GROOVY

AMIS – 26 november 2012

private String name;

public void setName(String name) {

this.name = name;

}

public String getName() {

return name;

}

OVER JAVA

• Academisch

• Uitgewerkt concept, Super uitgespecificeerd

• Bewezen

• Performant, Platform onafhankelijk

• Robust, Secure (?)

• Antiek

• Modern in 1995

• Vergelijk: C#, Python, Ruby, JavaScript, Smalltalk, Go

• Autistisch

import java.io.*;

import java.math.BigDecimal;

import java.net.*;

import java.util.*;

OVER JAVA – VERGELIJKING

Java

public class Pet {

private PetName name;

private Person owner;

public Pet(PetName name, Person owner) {

this.name = name;

this.owner = owner;

}

public PetName getName() {

return name;

}

public void setName(PetName name) {

this.name = name;

}

public Person getOwner() {

return owner;

}

public void setOwner(Person owner) {

this.owner = owner;

}

}

C#

public class Pet

{

public PetName Name { get; set; }

public Person Owner { get; set; }

}

OVER JAVA – VERGELIJKING

Java

Map<String, Integer> map =

new HashMap<String, Integer>();

map.put("een", 1);

map.put("twee", 2);

map.put("drie", 3);

map.put("vier", 4);

map.put("vijf", 5);

map.put("zes", 6);

Python

map = {'een':1, 'twee':2, 'drie':3,

'vier':4, 'vijf':5, 'zes':6}

OVER JAVA – VERGELIJKING

Java

FileInputStream fis = null;

InputStreamReader isr = null;

BufferedReader br = null;

try {

fis = new FileInputStream("file.txt");

isr = new InputStreamReader(fis);

br = new BufferedReader(isr);

String line;

while ((line = br.readLine()) != null) {

System.out.println(line);

}

} catch (IOException e) {

throw new RuntimeException(e);

} finally {

if (br != null)

try { br.close();

} catch (IOException e) { }

if (isr != null)

try { isr.close();

} catch (IOException e) { }

if (fis != null)

try { fis.close();

} catch (IOException e) { }

}

Python

with open('file.txt', 'r') as f:

for line in f:

print line,

OVER GROOVY

• Sinds: 2003

• Door: James Strachan

• Target: Java ontwikkelaars

• Basis: Java

• Plus: “Al het goede” van Ruby, Python en Smalltalk

• Apache Licence

• Uitgebreide community

• Ondersteund door SpringSource (VMWare)

• “The most under-rated language ever”

• “This language was clearly designed by very, very lazy

programmers.”

OVER GROOVY

• Draait in JVM

• Groovy class = Java class

• Perfecte integratie met Java

HELLO WORLD - JAVA

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());

}

}

HELLO WORLD - GROOVY

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());

}

}

HELLO WORLD - GROOVY

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());

}

}

HELLO WORLD - GROOVY

public class HelloWorld {

String 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());

}

}

HELLO WORLD - GROOVY

public class HelloWorld {

String 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());

}

}

HELLO WORLD - GROOVY

class HelloWorld {

String name

def greet() {

return "Hello " + name

}

static main(args) {

def helloWorld = new HelloWorld()

helloWorld.setName("Groovy")

System.out.println(helloWorld.greet())

}

}

HELLO WORLD - GROOVY

class HelloWorld {

String name

def greet() {

return "Hello " + name

}

static main(args) {

def helloWorld = new HelloWorld()

helloWorld.setName("Groovy")

System.out.println(helloWorld.greet())

}

}

name:"Groovy")

HELLO WORLD - GROOVY

class HelloWorld {

String name

def greet() { "Hello " + name }

static main(args) {

def helloWorld = new HelloWorld(name:"Groovy")

println(helloWorld.greet())

}

}

HELLO WORLD - GROOVY

class HelloWorld {

String name

def greet() { "Hello " + name }

static main(args) {

def helloWorld = new HelloWorld(name:"Groovy")

println(helloWorld.greet())

}

}

HELLO WORLD - GROOVY

class HelloWorld {

def name

def greet() { "Hello $name" }

}

def helloWorld = new HelloWorld(name:"Groovy")

println helloWorld.greet()

HELLO WORLD - GROOVY

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());

}

}

class HelloWorld {

def name

def greet() { "Hello $name" }

}

def helloWorld = new HelloWorld(name:"Groovy")

println helloWorld.greet()

GROOVY CONSOLE

GROOVY INTEGRATION

• Als Programmeertaal

– Compileert design-time

– Configuratie in Ant build script

GROOVY INTEGRATION - ANT

<?xml version="1.0" encoding="windows-1252" ?>

<project xmlns="antlib:org.apache.tools.ant" name="Project1">

...

<path id="groovy.lib" location="${workspace.dir}/groovy-all-2.0.1.jar"/>

...

<taskdef name="groovyc" classname="org.codehaus.groovy.ant.Groovyc“

classpathref="groovy.lib"/>

...

<target name="compile">

<groovyc srcdir="${src.dir}" destdir="${output.dir}">

<javac source="1.6" target="1.6"/>

</groovyc>

</target>

...

</project>

GROOVY INTEGRATION

• Als Programmeertaal

– Compileert design-time

– Configuratie in Ant build script

• Als Scripttaal

– Compileert run-time

• (Groovy compiler is geschreven in Java)

GROOVY INTEGRATION - SCRIPTING

GroovyShell gs = new GroovyShell();

Object result = gs.evaluate("...");

GROOVY FEATURES

• Native syntax

– Lists

def list = [1, 2, 3, 4]

– Maps:

def map = [nl: 'Nederland', be: 'Belgie']

assert map['nl'] == 'Nederland'

&& map.be == 'Belgie'

– Ranges:

def range = 11..36

– Regular Expressions

assert 'abc' ==~ /.\wc/

GROOVY FEATURES

• Native syntax (vervolg)

– GStrings

"Hello $name, it is now: ${new Date()}"

– Multiline Strings

def string = """Dit is regel 1.

Dit is regel 2."""

– Multiple assignment

def (a, b) = [1, 2]

(a, b) = [b, a]

def (p, q, r, s, t) = 1..5

GROOVY FEATURES

• New Operators

– Safe navigation (?.)

person?.adress?.streetname

in plaats van

person != null ? (person.getAddress() != null ?

person.getAddress().getStreetname() : null) :

null

– Elvis (?:)

username ?: 'Anoniem'

– Spaceship (<=>)

assert 'a' <=> 'b' == -1

GROOVY FEATURES

• Operator overloading

– Uitgebreid toegepast in GDK, voorbeelden:

def list = ['a', 'b', 1, 2, 3]

assert list + list == list * 2

assert list - ['a', 'b'] == [1, 2, 3]

new Date() + 1 // Een date morgen

GROOVY FEATURES

• Smart conversion (voorbeelden)

– to Numbers

def string = '123'

def nr = string as int

assert string.class.name == 'java.lang.String'

assert nr.class.name == 'java.lang.Integer'

– to Booleans (Groovy truth)

assert "" as boolean == false

if (string) { ... }

– to JSON

[a:1, b:2] as Json // {"a":1,"b":2}

– to interfaces

GROOVY FEATURES

• Closures

– (Anonieme) functie

• Kan worden uitgevoerd

• Kan parameters accepteren

• Kan een waarde retourneren

– Object

• Kan in variabele worden opgeslagen

• Kan als parameter worden meegegeven

– Voorbeeld:

new File('file.txt').eachLine({ line ->

println line

})

– Kan variabelen buiten eigen scope gebruiken

it

GROOVY FEATURES

• Groovy SQL

– Zeer mooie interface tegen JDBC

– Gebruikt GStrings voor queries

– Voorbeeld:

def search = 'Ki%'

def emps = sql.rows ( """select *

from employees

where first_name like $search

or last_name like $search""" )

GROOVY FEATURES

• Builders

– ‘Native syntax’ voor het opbouwen van:

• XML

• GUI (Swing)

• Json

• Ant taken

• …

– Op basis van Closures

GROOVY QUIZ

• Geldig?

def l = [ [a:1, b:2], [a:3, b:4] ]

def (m, n) = l

class Bean { def id, name }

new Bean().setName('Pieter')

[id:123, name:'Pieter'] as Bean

geef mij nu een kop koffie, snel

def

GROOVY FEATURES

• Categories

– Tijdelijke DSL (domain specific language)

– Breidt (bestaande) classes uit met extra functies

– Voorbeeld:

use(TimeCategory) {

newDate = (1.month + 1.week).from.now

}

GROOVY FEATURES

• (AST) Transformations

– Verder reduceren boiler plate code

– Enkele patterns worden meegeleverd, o.a.:

• @Singleton

• @Immutable / @Canonical

• @Lazy

• @Delegate (multiple inheritance!)

GROOVY CASES

• Java omgeving

– Als je werkt met: (ook in productie)

• Beans

• XML / HTML / JSON

• Bestanden / IO algemeen

• Database via JDBC

• Hardcore Java classes (minder boilerplate)

• DSL

• Rich clients (ook JavaFX)

– Functioneel programmeren in Java

– Prototyping

– Extreme dynamic classloading

• Shell scripting

GROOVY HANDSON

“ADF SCRIPTENGINE”

• Combinatie van:

– ADF

– Groovy

• met wat nieuwe constructies (“omdat het kan”)

• Features

– Programmaflow in Groovy

– Builder syntax voor tonen schermen in ADF

• Control state is volledig serialiseerbaar (high availability enzo)

– Bindings (à la EL ValueBindings)

– Mooie API (à la Grails) richting Model (bijv. ADF BC,

WebServices, etc...)

“ADF SCRIPTENGINE”

• Voorbeeld script

– Handmatig aanvullen lege elementen in een XML fragment

GROOVY TEASER

• Method parameters with defaults

• Method with named parameters

• Creating Groovy API’s

• Runtime meta-programming

• Compile-time meta-programming

• Interceptors

• Advanced OO (Groovy interfaces)

• GUI’s

• …