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Tecnologie Groovy
Prima Parte
Giugno 2013
Francesco Lerro
venerdì 28 giugno 13

Obiettivi del talk
• Mostrare le peculiarità del linguaggio
• Introdurre alcuni tool legati a Groovy
• Farvi venire voglia di provarlo :)

import java.util.List;
import java.util.ArrayList;
class Filter {
! static List<String> filterLongerThan(List<String> xs, int maxLen) {
! ! List<String> results = new ArrayList<String>();
! ! for (int i=0; i < xs.size(); i++){
! ! ! String s = xs.get(i);
! ! ! if (s.length() <= maxLen){
! ! ! ! results.add(s);
! ! ! }
! ! }
! ! return results;
! }
! public static void main(String[] args) {
! ! List<String> names = new ArrayList<String>();
! ! names.add("Giulio"); names.add("Laura");
! ! names.add("Mario"); names.add("Anna");
! ! System.out.println(names);
! ! List<String> shortNames = filterLongerThan(names, 5);
! ! System.out.println("After filtering: " + shortNames.size());
! ! for (int i=0; i < shortNames.size(); i++) {
! ! ! String s = shortNames.get(i);
! ! ! System.out.println(s);
! ! }
! }
}

class Filter {
! static List<String> filterLongerThan(List<String> xs, int maxLen) {
! ! List<String> results = []
! ! for (int i=0; i < xs.size(); i++){
! ! ! String s = xs[i]
! ! ! if (s.length() <= maxLen){
! ! ! ! results << s
! ! ! }
! ! }
! ! return results;
! }
! public static void main(String[] args) {
! ! List<String> names = ["Giulio", "Laura", "Mario", "Anna"]
! ! System.out.println(names);
! ! List<String> shortNames = filterLongerThan(names, 5);
! ! System.out.println("After filtering: " + shortNames.size());
! ! for (int i=0; i < shortNames.size(); i++) {
! ! ! String s = shortNames[i]
! ! ! System.out.println(s);
! ! }
! }
}

class Filter {
static List<String> filterLongerThan(List<String> xs, int maxLen) {
List<String> results = []
for (int i=0; i < xs.size(); i++){
String s = xs[i]
if (s.length() <= maxLen){
results << s
}
}
return results;
}
public static void main(String[] args) {
List<String> names = ["Giulio", "Laura", "Mario", "Anna"]
System.out.println(names);
List<String> shortNames = filterLongerThan(names, 5);
System.out.println("After filtering: " + shortNames.size());
for (int i=0; i < shortNames.size(); i++) {
String s = shortNames[i];
System.out.println(s);
}
}
}

class Filter {
xs.each { s ->
if (s.length() <= maxLen){
results << s
}
}
return results;
}
println(names);
println("After filtering: " + shortNames.size());
shortNames.each { println(it) }
}
}

class Filter {
results = xs.findAll { s -> s.length() <= maxLen }
return results;
}
println(names)
List<String> shortNames = filterLongerThan(names, 5)
println("After filtering: " + shortNames.size())
}
}

class Filter {
xs.findAll { s -> s.length() <= maxLen }
}
println(names);
println("After filtering: " + shortNames.size());
}
}

class Filter {
}
println(names)
println("After filtering: " + shortNames.size())
}
}

class Filter {
}
println(names)
println("After filtering: ${shortNames.size()}")
}
}

class Filter {
int maxLen = 5
println(names)
List<String> shortNames = names.findAll { s -> s.length() <= maxLen }
}
}
-70%

class Filter {
int maxLen = 5
println(names)
List<String> shortNames = names.findAll { s -> s.length() <= maxLen }
}
}

+
Smalltalk {

+
optionally typed,
dinamico,
funzionale

Opzionalmente tipizzato

Dinamico
• Aggiunta a compile-time di funzionalità:
metodi, propietà, costruttori
• Runtime mixins ed invocazione di metodi il
cui nome risiede in una variabile

Dinamico - ExpandoMetaClass

Dinamico - ExpandoMetaClass
Aggiunta funzionalità a
compile-time anche se final

Dinamico - Metodi su collection

Dinamico - Mixin di metodi
@Category(Vehicle) class FlyingAbility {
def fly() { "${name}: fly!" }
}
@Category(Vehicle) class DivingAbility {
def dive() { "${name}: dive!" }
}
interface Vehicle {
String getName()
}
@Mixin(FlyingAbility)
class Plane implements Vehicle {
String getName() { "Concorde" }
}
@Mixin([DivingAbility, FlyingAbility])
class JamesBondVehicle implements Vehicle {
String getName() { "James Bond's vehicle" }
}
assert new Plane().fly() == "Concorde: fly!"
assert new JamesBondVehicle().fly() == "James Bond's vehicle: fly!"
assert new JamesBondVehicle().dive() == "James Bond's vehicle: dive!"

Dinamico - Via annotation
• Iniezione funzionalità via annotation
• @Immutable (@Canonical)
• @Bindable
• @Delegate
• @Newify
• @Lazy
• @Log
• etc.

Dinamico - Esempio @Delegate

Funzionale
• Funzioni come first class citizens (Closure)
• associabili ad una variabile
• usate come parametri di altre funzioni
• componibili
• zucchero sintattico

Funzionale - Esempio di currying

La Groovy “verità”
• Regole per la coercizione in boolean
• Collezioni: true se NON vuote
• Stringhe: true se NON vuote o nulle
• Oggetti: true se NON nulli
• Regexp Pattern: true se MATCH

Groovy truth - Esempi

Groovy truth - Esempi
Usa gli operatori ?. e ?: in
combinazione per evitare NPE

Builder

Slurper
<?xml version="1.0" ?>
<customers>
<customer name="Mario Rossi" />
<customer name="Giovanni Bianchi" />
</customers>
import java.io.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
public class XMLReader {
public static void main(String argv[]) throws Exception {
File file = new File("customers.xml");
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(file);
doc.getDocumentElement().normalize();
NodeList nodeLst = doc.getElementsByTagName("customer");
for (int s = 0; s < nodeLst.getLength(); s++) {
Element item = (Element) nodeLst.item(s);
System.out.println(item.getAttribute("name"));
}
}
}

Slurper
<?xml version="1.0" ?>
<customers>
<customer name="Mario Rossi" />
<customer name="Giovanni Bianchi" />
</customers>
def xmlFile = new File('customers.xml')
def xml = new XmlSlurper().parse(xmlFile)
xml.customer.each {
println it.'@name'.text()
}
Anche per JSON, Config, ...

Performance
• Dinamico implica overhead
• spesso diversi punti %
• Molti miglioramenti da Groovy 2.0
• primitiva invokeDynamic (Java 7)
• @CompileStatic
• Valutare trade-off produttività VS velocità

Performance...
@Grab('com.googlecode.gbench:gbench:0.4.2-groovy-2.1')
import gbench.BenchmarkBuilder
import groovy.transform.CompileStatic
int fib(int n) {
if (n < 2) return n
return fib(n - 1) + fib(n - 2)
}
@CompileStatic
int fib2(int n) {
if (n < 2) return n
return fib2(n - 1) + fib2(n - 2)
}
new BenchmarkBuilder().run {
int n = 20
"Normal Version" { fib n }
"@CompileStatic Version" { fib2 n }
}.prettyPrint()

Performance...
@Grab('com.googlecode.gbench:gbench:0.4.2-groovy-2.1')
import gbench.BenchmarkBuilder
import groovy.transform.CompileStatic
int fib(int n) {
if (n < 2) return n
return fib(n - 1) + fib(n - 2)
}
@CompileStatic
int fib2(int n) {
if (n < 2) return n
return fib2(n - 1) + fib2(n - 2)
}
new BenchmarkBuilder().run {
int n = 20
"Normal Version" { fib n }
"@CompileStatic Version" { fib2 n }
}.prettyPrint()
* JVM: Java HotSpot(TM) 64-Bit Server VM (23.6-b04...
* JRE: 1.7.0_10
* Total Memory: 81.1875 MB
* Maximum Memory: 1123.5625 MB
* OS: Mac OS X (10.7.5, x86_64)
Options
=======
* Warm Up: Auto
* CPU Time Measurement: On
user system cpu real
Normal Version 92622 7 92630 92626
@CompileStatic Version 39974 3 39977 39976

Ecosistema
Geb, Spock, WSLite...

Ecosistema
Nella seconda parte
approfondiremo il discorso
su queste tecnologie!
Geb, Spock, WSLite...

Riferimenti
• Groovy User Guide - http://groovy.codehaus.org/User+Guide
• Bob Brown - The future is Gr8 - http://wordpress.transentia.com.au/wordpress/
2013/05/07/disaster/
• Sergey Dolgopolov - Testing the performance of new Groovy 2.0 release with
GBench - http://www.sergeydolgopolov.me/2012/07/groovy-20-has-been-released-testing-
new.html
• Guillame Laforge - Groovy Ecosystem - http://www.slideshare.net/glaforge/groovy-ecosystem-
jfokus-2011-guillaume-laforge
• Hubert Klein Ikkink (aka mrhaki) - Groovy goodness blog -
http://mrhaki.blogspot.it/
• Geb Samples - http://www.gebish.org
• GPars Samples for Dataflow and Actors - http://gpars.codehaus.org
• Spock Samples - http://code.google.com/p/spock/
• Tim Myer - http://timezra.blogspot.it/2011/11/trampoline-and-memoize.html

Web: http://rolandfg.net Twitter: @flerro

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Groovy: il linguaggio

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