A Tour Through the Groovy Ecosystem

A Tour Through the Groovy Ecosystem
at

Examples available on Github
https://github.com/xlson/presentations/tree/master/
groovy-ecosystem-dyncon_2011

Saturday, March 12, 2011

Leonard Axelsson
• Groovy developer since 2007
• Co-Founder of SweGUG
–Swedish Groovy User Group
• Speaker at Javaforum,
GTUG, Agical Geeknight,
JFokus, SweGUG @xlson
• Developer/Consultant at http://xlson.com/
Agical


a long long time ago
(4 years or so ;)


Overview
• Part 1: Groovy intro ~15 mins

• Short and sweet

• Part 2: Ecosystem ~20 mins

• Mapping the wilderness

• Part 3: Questions?!?!? :)


Groovy Overview

• Originated in 2003

• Under the Apache License

• Runs on the Java Virtual Machine

• Grammar derived from Java 1.5


Groovy Overview
• Dynamic language

• Inspired by Python, Ruby and Smalltalk

• Object Oriented

• Easy to learn for Java devs

• Supports Java style code out of the box

• Scriptable

• Embeddable


Dynamic Language
• No compile-time checking

• int i = “Hello” throws exception at runtime

• Ducktyping

• def keyword allows you to care about what
the object does, not what it is

• Supports custom DSLs
new DateDSL().last.day.in.december( 2009 )

http://groovyconsole.appspot.com/view.groovy?id=27001


The obligatory Hello
World


How many in here
know Groovy?


Ok, so how many in here know
some Java?


HelloWorld.java
class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}


HelloWorld.groovy
class HelloWorld {
}
}


Removing ...
class HelloWorld {
}
}


Removing ...
class HelloWorld {
System.out.println("Hello World!")
}
}


Removing ...
class HelloWorld {
println("Hello World!")
}
}


Removing ...
println("Hello World!")


This is it
println "Hello World!"


Feature Overview
• Properties

• dynamic getters and setters

• Closures

• reusable blocks of code

• Meta Object Protocol

• rewrite behaviour at runtime

• Many additions to the JDK


Primitives are objects
to
int a = 5 // Normal string
long b = 1 String message = 'got $5?'
float f = 5.4
double d = 5.4 // Double quoted string supports macros
String longerMessage = "Have you $message"

// Multiline strings available as well
String email = """Hi!
How are you?

/Leo"""

println message
println longerMessage
println email


Plain Old Groovy
Objects


POGO’s
• Properties

• getters and setters are created
automatically


POGO’s
• Properties

• getters and setters are created
automatically

• Named Parameters

• clariﬁes intent


POGO’s

class Person {
String name
String lastname
}

def anders = new Person(name: 'Anders', lastname: 'Andersson')
assert anders.getName() == 'Anders'

// Anders gets married and changes his lastname
anders.setLastname("Sundstedt")
assert anders.lastname == "Sundstedt"


POGO’s
• Getters and setters can be overridden
class Person {
def name
def lastname

String setLastname(String lastname) {
this.lastname = lastname.reverse()
}
}

def anders = new Person(name: 'Anders', lastname: 'Andersson')

// Anders does a strange change of his lastname
anders.lastname = "Sundstedt"
assert anders.lastname == "tdetsdnuS"


Built in syntax for lists
and maps


Lists
List syntax:
def names = ['Leonard', 'Anna', 'Anders']
assert names instanceof List
assert names.size() == 3
assert names[0] == 'Leonard'


Maps
def map = [name: 'Leonard',
lastname: 'Axelsson']
assert map.name == 'Leonard'
assert map['lastname'] == 'Axelsson'

map.each{ key, value ->
println "Key: $key, Value: $value"
}

Output:
Key: name, Value: Leonard
Key: lastname, Value: Axelsson


each, ﬁnd and ﬁndAll
class Person {
String name
String lastname
boolean male
}

def ages = [new Person(name: 'Bo', lastname: 'Olsson', male: true),
new Person(name: 'Gunn', lastname: 'Bertilsson', male: false),
new Person(name: 'Britt', lastname: 'Olsson', male: false)]
// Print all names
ages.each { println "$it.name $it.lastname" }

// Find one male
assert ages.find{ person -> person.male }.name == 'Bo'

// or find all females
assert ages.findAll{ Person p -> !p.male }.size() == 2


Putting the basics
together

(0..7).collect{(('a'..'z')+('A'..'Z')+(0..9))[new Random().nextInt(62)]}.join()


AST Transformations
Compile-time meta programming


@Log

import groovy.util.logging.*

@Log
class LogDemo {

def usesLogger() {
log.info "Uses the log annotation."
}

static void main(String[] args) {
new LogDemo().usesLogger()
}
}


@Immutable
import groovy.transform.*

@Immutable
class User {
String name
String lastname
}

def user = new User(name: 'Leo', lastname: 'Axelsson')

try {
user.name = 'Anders'
} catch(ReadOnlyPropertyException e) {
println("Changing a property of an Immutable object will not work.")
}

println user


@EqualsAndHashCode

import groovy.transform.*

@EqualsAndHashCode
class User {
String name
String lastname
}

def user1 = new User(name: 'Leo', lastname: 'Axelsson')
def user2 = new User(name: 'Leo', lastname: 'Axelsson')

assert user1 == user2


Mapping the
ecosystem
So, we’ve already started, but let’s do some more
sightseeing...


GPars
• Parallelization framework

• Features

• Actors

• Agents

• Dataﬂow

• Parallell Collection Processing


GPars
@Grab(group='org.codehaus.gpars', module='gpars', version='0.10')
import groovyx.gpars.GParsExecutorsPool

def importProcessingData = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 ,18, 19, 20]

time('Parallel execution') {
GParsExecutorsPool.withPool {
importProcessingData.eachParallel { data ->
// Insert arbitrary heavy operation here
sleep 200
}

}
}

time('Linear execution') {
importProcessingData.each {
// Insert arbitrary heavy operation here
sleep 200
}
}

def time(String desc, task) {
def startTime = new Date().time
def result = task()
def executionTime = new Date().time - startTime
println "$desc took: $executionTime ms."
result
}


GPars
• Output (executed on dual-core machine):
Parallel execution took: 1449 ms.
Linear execution took: 4006 ms.


@Grab and grape
• Dependency management using Apache Ivy

• Uses Maven Central

• grape

• Commandline tool to manage dependencies

• @Grab annotation

• Provides dependcies in scripts


Web


Grails
• Convention Over Conﬁguration

• Used on one of Great Britains biggest(?)
public sites: Sky.com

• Stands upon the shoulders of giants

• Rich plugin system


Grails
-14 :20
• Convention Over Conﬁguration
13 :40
ow at
orr ! :)
tom rrien biggest(?)
• Used on one of Great Britains s
ails k Ju
public sites:r Sky.com
ou tG en
ab with H
ore
M • Stands upon the shoulders of giants
• Rich plugin system


Testing,
what to say about testing...
• Spock

• EasyB

• GroovyTestCase

• MockFor()

• Expandos and Maps

• Geb

• SoapUI

• Groovy Remote Control


Spock

• Great testing framework

• Easy to read (and write)


Spock:
Readable tests
@Grab('org.spockframework:spock-core:0.5-groovy-1.8')
@GrabExclude('org.codehaus.groovy:groovy-all:1.8.0-beta-3')
import spock.lang.*

class ReadableSpec extends Specification {

def "All is well in math-land"() {
expect:
sum == a + b

where:
a | b | sum
1 | 5 | 6
6 | 2 | 8
}
}


Spock:
Unroll your tests
@Grab('org.spockframework:spock-core:0.5-groovy-1.8')
@GrabExclude('org.codehaus.groovy:groovy-all:1.8.0-beta-3')
import spock.lang.*

class UnrolledSpec extends Specification {

@Unroll({"The sum of $a and $b should be $sum."})
def "All is well in math-land"() {
expect:
sum == a + b

where:
a | b | sum
1 | 5 | 6
6 | 2 | 8
10 | 2 | 11
}
}


Geb
• Wanna surf programmatically?

• Geb == really nice and easy browser
automation

• jQuery style for navigation API

• even supports calling out to jQuery

• Page objects


Geb:
Headless Browsing

@Grab('org.codehaus.geb:geb-core:0.5.1')
@Grab('org.seleniumhq.selenium:selenium-htmlunit-driver:2.0a7')
import geb.Browser

Browser.drive("http://xlson.com/") {
assert title == "Leonard Axelsson"
}


Geb:
Finding Dyncon using Firefox
@Grab('org.codehaus.geb:geb-core:0.5.1')
@Grab('org.seleniumhq.selenium:selenium-firefox-driver:2.0a7')
import geb.Browser

Browser.drive("http://google.se/") {
assert title == 'Google'
$("input", name: "q").value("Dyncon 2011")
$("input", name: "btnG").click()

waitFor { title.startsWith("Dyncon 2011") }

def firstLink = $("li.g", 0).find("a.l")
assert firstLink.text() == "Dyncon 2011"
firstLink.click()
}


Building


AntBuilder

• Gives you the power of Ant in Groovy

• ..the power of what?

• Well, platform independent ﬁle handling
among other things


AntBuilder
def ant = new AntBuilder()

// lets just call one task
ant.echo("hello")

// here is an example of a block of Ant inside GroovyMarkup
ant.sequential {
echo("inside sequential")
myDir = "target/AntTest/"
mkdir(dir:myDir)
copy(todir:myDir) {
fileset(dir:"src/test") {
include(name:"**/*.groovy")
}
}
echo("done")
}

// now lets do some normal Groovy again
file = new File("target/AntTest/groovy/util/AntTest.groovy")
assert file.exists()


Gradle
• Easy to get started with

• Bye bye ‘copy-paste’-pattern

• Declarative OR Build by Convention

• Extremely Extendable

• Integrates with Ivy for dependency
management


Gradle:
Highlights
• Easy for the ﬁrst 80% of functionality

• ...easy for the 20% last as well

• Keeps track of what’s changed

• Works everywhere thanks to the Gradle
Wrapper


Gradle:
Simply Groovy
apply plugin: 'groovy'
apply plugin: 'application'

repositories {
mavenCentral()
}

dependencies {
groovy 'org.codehaus.groovy:groovy-all:1.7.9'
}

mainClassName='HelloWorld'


Gradle:
Multiproject

• Head out to the code... :)


Other goodies


Griffon

• Grails for the desktop

• Early days but lots of plugins

• DSL for Swing

• Extends SwingBuilder


GroovyServ

• Speeds up execution of Groovy scripts

• Groovy for small utils ﬁnally valid!


GroovyServ:
Pretty XML on the commandline

#!/usr/bin/env groovyclient

println(prettyPrintXml(System.in.text))

def prettyPrintXml(text) {
def xmlNode = new XmlParser().parseText(text)
def writer = new StringWriter()
def printer = new XmlNodePrinter(new PrintWriter(writer))
printer.preserveWhitespace = true
printer.print(xmlNode)
writer.toString().trim()
}


Links
• Groovy

• http://groovy.codehaus.org/

• Groovy Goodness (great tips and trix)

• http://mrhaki.blogspot.com/

• Groovy Web Console (on Appengine)

• http://groovyconsole.appspot.com/

• My blog

• http://xlson.com/

• SweGUG

• http://groups.google.com/group/swegug


A Tour Through the Groovy Ecosystem

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