groovy fly through

Fly Through

Who?

<niklas.lindstrom@valtech.se>

@niklasl

Trust me?

Used dynamic langs on the JVM since 2000.

Groovy since 2004/2007

What?

A Dynamic Language for the JVM

A modern language

Inspired by best features:

JavaRuby

PythonSmalltalk

...

Java

The Premise

The Platform

Exciting?

Modern GC

JIT

Puts hardware to good use(mem, multi-core, I/O)

Java = Community

Well-established libraries (jdk, commons, ...).

Loads of opens source stuff.

Evolution

Groovy extends Java.

Really. 100% semantically, 90% syntactically.

CreativeTools

What does it look like?

class First {

static void main(String[] args) { println "You just gave me " + args[0] }

}

Shorter

println "You just gave me ${args[0]}"

Many Variants

class Think {

String value

def getMeaning() { "You just gave me ${value}." }

static main(args) { def first = args? args[0] : "nothing" println new Think(value:first).meaning }

}

Usages

Everywhere.

Groovy classes are real classes in Java.

Cherry-pick

● Small scripts● API experimentation● Tools for batch and analysis● Tests, Specs● Building

Entire applications

Seamlessly cross-compiles with Java.

Write any or all parts in Groovy, using any Java framework.

Ceremonypublic class Item {

private String name; private String description;

public Item() {}

public String getName() { return name; }

public String setName(String name) { this.name = name; }

public String getDescription() { return description; }

public void setDescription(String description) { this.description = description; }

}

Pragmatic

class Item { String name String description}

Compact Properties

new Date().time // same as getTime()

Dynamic

def v = "string.."v = 1

assert v instanceof String

No cast needed

Just access methods and properties expected to be there.

But..

Types have significance..

Type Hybrid

Dynamic refs are declared with def.

Typed refs are auto-cast & converted:

String v = 123v.bytes[-1] == '3'

GroovyCastException

Date dd = "hi!"

Small Values of Cool

Optional Parens

client.sendMessage "Message: ${msg}"

client.quit()

Access else null

response?.entity

Use all

files*.name

Slice

def l = ['a', 'b', 'c', 'd']

assert l[1..-2] == ['b', 'c']

Map Expandos

Map map = ['a': 1, b: 2]

assert map['a'] == 1assert map.b == 2

map.c = 3map['d'] = 3

assert map['c'] == map.d

Closures

Code block literals.

Syntax:

def items = ["a", "b", "c", "def"]

items.eachWithIndex { item, i -> println "${i+1}: ${item}"}

Sift and Transform

def values = ["1", "2", "12", "123"]

def some = values.findAll { it.size() > 1 }

def ints = some.collect { (it as int) * 2 }

assert ints == [24, 246]

GDK

new File("urls.txt").eachLine {

def url = new URL(it)

def file = new File("./${url.path}")

file.parentFile.mkdirs()

file.bytes = url.bytes

}

Xml...

def slurper = new XmlSlurper()def html = slurper.parse(new File("/some.xhtml"))

html.body.'*'.each { println it.'@id'}

Spock

def "lists should be appendable"() { given: def a = []

when: a << 1

then: a == [1]}

Mocks

EventHandler handler = Mock()

handler.handle(someAllowedEvent) >> true

handler.handle(_) >> false

Data-driven

expect:a.toUpperCase() == bwhere: a | b"a" | "A""b" | "B""c" | "C""d" | "D"

PowerAsserts

assert a == [1]

ERROR org.codehaus.groovy.tr...rt.PowerAssertionError:assert a == [1] | | | false []

Environments

Scripts

$ groovy setup_db.groovy

REPL

$ groovyshgroovy:000> import org.apache.commons.io.*

Groovy Console

Building

Ant

Maven

Gradle

Grab with Grape

@Grab('org.mortbay.jetty:jetty-embedded:6.1.0')import org.mortbay.jetty.Server

def server = new Server(8080)server.start()

IDE:s

Amazing IntelliJ support.

Eclipse known to be good..

The Power of Prototyping

"You can use Groovy asan exploratory languagefor functionality spikes."

More Info

<http://groovy.codehaus.org/>

<http://spockframework.org/>

.. the web is full of groovy:

<http://groovyconsole.appspot.com/>

Groovy Style For the Java Guy

Thank you!

CC Images

Groovy-logo, "Groovy Duke"

"Tools""Shell""Tadpole"