Paco van der Linden, werkzaam als Senior ADF Ontwikkelaar bij AMIS, heeft met Groovy een aantal interessante oplossingen ontwikkeld. De kennis en ervaring die hij daarbij met Groovy in combinatie met Java (en ADF) heeft opgedaan, heeft hij op maandag 26 november gedeeld in een kennissessie.

1. AMIS – 26 november 2012
INTRODUCTIE IN GROOVY

2. 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
private String name;
public void setName(String name) {
this.name = name;
}
import java.io.*;
import java.math.BigDecimal;
public String getName() {
import java.net.*;
return name;
import java.util.*;
}

3. OVER JAVA – VERGELIJKING
Java C#
public class Pet { public class Pet
private PetName name; {
private Person owner; public PetName Name { get; set; }
public Person Owner { get; set; }
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;
}
}

4. OVER JAVA – VERGELIJKING
Java Python
Map<String, Integer> map = map = {'een':1, 'twee':2, 'drie':3,
new HashMap<String, Integer>(); 'vier':4, 'vijf':5, 'zes':6}
map.put("een", 1);
map.put("twee", 2);
map.put("drie", 3);
map.put("vier", 4);
map.put("vijf", 5);
map.put("zes", 6);

5. OVER JAVA – VERGELIJKING
Java Python
FileInputStream fis = null; with open('file.txt', 'r') as f:
InputStreamReader isr = null; for line in f:
BufferedReader br = null; print line,
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) { }
}

6. 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.”

7. OVER GROOVY
• Draait in JVM
• Groovy class = Java class
• Perfecte integratie met Java

8. 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());
}
}

9. 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());
}
}

10. 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());
}
}

11. 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());
}
}

12. 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());
}
}

13. 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())
}
}

14. HELLO WORLD - GROOVY
class HelloWorld {
String name
def greet() {
return "Hello " + name
}
static main(args) {
name:"Groovy")
def helloWorld = new HelloWorld()
helloWorld.setName("Groovy")
System.out.println(helloWorld.greet())
}
}

15. HELLO WORLD - GROOVY
class HelloWorld {
String name
def greet() { "Hello " + name }
static main(args) {
def helloWorld = new HelloWorld(name:"Groovy")
println(helloWorld.greet())
}
}

16. HELLO WORLD - GROOVY
class HelloWorld {
String name
def greet() { "Hello " + name }
static main(args) {
def helloWorld = new HelloWorld(name:"Groovy")
println(helloWorld.greet())
}
}

17. HELLO WORLD - GROOVY
class HelloWorld {
def name
def greet() { "Hello $name" }
}
def helloWorld = new HelloWorld(name:"Groovy")
println helloWorld.greet()

18. HELLO WORLD - GROOVY
public class HelloWorld { class HelloWorld {
def name
private String name; def greet() { "Hello $name" }
}
public void setName(String name) {
this.name = name; def helloWorld = new HelloWorld(name:"Groovy")
} println helloWorld.greet()
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());
}
}

19. GROOVY CONSOLE

20. GROOVY INTEGRATION
• Als Programmeertaal
– Compileert design-time
– Configuratie in Ant build script

21. 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>

22. GROOVY INTEGRATION
• Als Programmeertaal
– Compileert design-time
– Configuratie in Ant build script
• Als Scripttaal
– Compileert run-time
• (Groovy compiler is geschreven in Java)

23. GROOVY INTEGRATION - SCRIPTING
GroovyShell gs = new GroovyShell();
Object result = gs.evaluate("...");

24. 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/

25. 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

26. 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

27. 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

28. 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

29. 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 it
line
})
– Kan variabelen buiten eigen scope gebruiken

30. 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""" )

31. GROOVY FEATURES
• Builders
– ‘Native syntax’ voor het opbouwen van:
• XML
• GUI (Swing)
• Json
• Ant taken
• …
– Op basis van Closures

32. GROOVY QUIZ
• Geldig?
def l = [ [a:1, b:2], [a:3, b:4] ]
def (m, n) = l
class Bean { def id, name }
def
new Bean().setName('Pieter')
[id:123, name:'Pieter'] as Bean
geef mij nu een kop koffie, snel

33. 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
}

34. GROOVY FEATURES
• (AST) Transformations
– Verder reduceren boiler plate code
– Enkele patterns worden meegeleverd, o.a.:
• @Singleton
• @Immutable / @Canonical
• @Lazy
• @Delegate (multiple inheritance!)

35. 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

36. GROOVY HANDSON

37. “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...)

38. “ADF SCRIPTENGINE”
• Voorbeeld script
– Handmatig aanvullen lege elementen in een XML fragment

39. 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
• …