Groovy to infinity and beyond - GR8Conf Europe 2010 - Guillaume Laforge

to Infinity
and Beyond
mercredi 19 mai 2010

to infinity
and beyond!

Guillaume Laforge
SpringSource, a division of VMWare


Guillaume Laforge
Groovy Project Manager
on Groovy since 2003!
JSR-241 Spec Lead
Head of Groovy Development
at SpringSource (division of VMWare)
Initiator of the Grails framework
Creator of the Gaelyk toolkit
Co-author of Groovy in Action
International speaker


Agenda
Past
Groovy 1.6 ﬂashback

Present
Groovy 1.7 novelties
A few Groovy 1.7.x reﬁnements

Future
What’s cooking for 1.8 and beyond


looking into the Past

Big highlights of Groovy 1.6
Greater compile-time and runtime performance
Multiple assignments
Optional return for if/else and try/catch/ﬁnally
Java 5 annotation deﬁnition
AST Transformations
The Grape module and dependency system
Various Swing related improvements
JMX Builder
Metaprogramming additions
JSR-223 scripting engine built-in
Out-of-the-box OSGi support


Multiple assignement
// multiple assignment
def (a, b) = [1, 2]
assert a == 1 && b == 2

// with typed variables
def (int c, String d) = [3, "Hi"]
assert c == 3 && d == "Hi"

def geocode(String place) { [48.8, 2.3] }
def lat, lng
// assignment to existing variables
(lat, lng) = geocode('Paris')

// classical variable swaping example
(a, b) = [b, a]


More optional return
// optional return for if statements
def m1() {
    if (true) 1
    else 0
}
assert m1() == 1

// optional return for try/catch/finally
def m2(bool) {
    try {
        if (b) throw new Exception()
        1
    } catch (any) { 2 }
    finally { 3 }
}
assert m2(true) == 2 && m2(false) == 1


AST Transformation (1/2)
Groovy 1.6 introduced AST Transformations
AST: Abstract Syntax Tree
Ability to change what’s being compiled by the
Groovy compiler... at compile time
No runtime impact!
Change the semantics of your programs! Even hijack the
Groovy syntax!
Implementing recurring patterns in your code base
Remove boiler-plate code
Two kinds: global and local (triggered by anno)


AST Transformations (2/2)
Transformations introduced in 1.6
@Singleton
@Immutable, @Lazy, @Delegate
@Newify
@Category, @Mixin
@PackageScope
Swing’s @Bindable and @Vetoable
Grape’s own @Grab


@Immutable
To properly implement immutable classes
No mutations — state musn’t change
Private ﬁnal ﬁelds
Defensive copying of mutable components
Proper equals() / hashCode() / toString()
for comparisons or fas keys in maps
@Immutable class Coordinates {
Double lat, lng
}
def c1 = new Coordinates(lat: 48.8, lng: 2.5)
def c2 = new Coordinates(48.8, 2.5)
assert c1 == c2


Grab a grape!
Simple distribution and sharing of Groovy scripts
Dependencies stored locally
Can even use your own local repositories

@Grab(group   = 'org.mortbay.jetty',
      module  = 'jetty‐embedded',
      version = '6.1.0')
def startServer() {
    def srv = new Server(8080)
SIONS)
    def ctx = new Context(srv , "/", SES
    ctx.resourceBase = "."
ovy")
     ctx.addServlet(GroovyServlet, "*.gro
    srv.start()
}


Metaprogramming additions (1/2)
ExpandoMetaClass DSL
factoring EMC changes

Number.metaClass {
    multiply { Amount amount ‐>
        amount.times(delegate)
    }
    div { Amount amount ‐>
        amount.inverse().times(delegate)
    }
}


Metaprogramming additions (2/2)
Runtime mixins
class FlyingAbility {
    def fly() { "I'm ${name} and I fly!" }
}

class JamesBondVehicle {
    String getName() { "James Bond's vehicle" }
}

JamesBondVehicle.mixin FlyingAbility

assert new JamesBondVehicle().fly() ==
    "I'm James Bond's vehicle and I fly!"


JMX Builder
A DSL for handling JMX
in addition of Groovy MBean
// Create a connector server
def jmx = new JmxBuilder()
jmx.connectorServer(port:9000).start()

// Create a connector client
jmx.connectorClient(port:9000).connect()

//Export a bean
jmx.export { bean new MyService() }

// Defining a timer
jmx.timer(name: "jmx.builder:type=Timer",
event: "heartbeat", period: "1s").start()

// JMX listener
jmx.listener(event: "someEvent", from: "bean",
call: { evt ‐> /* do something */ })


into the Present...

Big highlights of Groovy 1.7
Anonymous Inner Classes and Nested Classes
Annotations anywhere
Grape improvements
Power Asserts
AST Viewer
AST Builder
Customize the Groovy Truth!
Rewrite of the GroovyScriptEngine
Groovy Console improvements
SQL support reﬁnements


AIC and NC
Anonymous Inner Classe and Nested Classes


AIC and NC
Anonymous Inner Classe and Nested Classes

For J ava
pa ste
co py’n
pa tibi lity
com
sak e :-)


Annonymous Inner Classes
bo olean called = false
Timer ti mer = new Timer()

timer.schedule(n ew TimerTask() {
    void run() {
         called = true
    }
}, 0)

sleep 100
assert called


Annonymous Inner Classes
bo olean called = false
Timer ti mer = new Timer()

timer.schedule(n ew TimerTask() {
    void run() {
         called = true
    }
{ called = true }
}, 0) as TimerTask

sleep 100
assert called


Nested Classes

class Environment {
    static class Production
         extends Environment {}
    static class Development
         extends Environment {}
}

new Environment.Production()


Anotations anywhere

You can now put annotations
on imports
on packages
on variable declarations

Examples with @Grab following...


Grape improvements (1/3)
@Grab on import

@Grab(group = 'net.sf.json‐lib',
     module = 'json‐lib',
    version = '2.3',
classifier = 'jdk15')
import net.sf.json.groovy.*

assert new JsonSlurper().parseText(
new JsonGroovyBuilder().json {
    book(title: "Groovy in Action",
        author:"Dierk König et al")
ion"
}.toString()).book.title == "Groovy in Act


Shorter module / artifact / version parameter
Example of an annotation on a variable declaration

@Grab('net.sf.json‐lib:json‐lib:2.3:jdk15')
()
def builder = new net.sf.json.groovy.JsonGroovyBuilder

def books = builder.books {
nig")
    book(title: "Groovy in Action", author: "Dierk Koe
}
assert books.toString() ==
    '{"books":{"book":{"title":"Groovy in Action",' +
    '"author":"Dierk Koenig"}}}'''


Groovy 1.7 introduced Grab resolver
For when you need to specify a speciﬁc repository
for a given dependency

@GrabResolver(
name = 'restlet.org',
root = 'http://maven.restlet.org')
@Grab('org.restlet:org.restlet:1.1.6')
import org.restlet.Restlet


Power Asserts (1/2)
Much better assert statement!
Invented and developed in the Spock framework

Given this script...

def energy = 7200 * 10**15 + 1
def mass = 80
def celerity = 300000000

assert energy == mass * celerity ** 2


Power Asserts (2/2)
You’ll get a more comprehensible output


Spock testing
framework

Easier AST Transformations
AST Transformations are a very powerful feature
But are still rather hard to develop
Need to know the AST API closely

To help with authoring your own transformations,
we’ve introduced
the AST Viewer in the Groovy Console
the AST Builder


AST Viewer


AST Builder
// Ability to build AST parts
// ‐‐> from a String
new AstBui lder().buildFromString(''' "Hello" ''')

// ‐‐> from code
new AstBuilder().buildFromCode { "Hello" }

// ‐‐> from a specification
{
List<ASTNo de> nodes = new AstBuilder().buildFromSpec
    block {
        returnStatement {
            constant "Hello"
        }
    }
}


Customize the Groovy Truth!
Ability to customize the truth by implementing a
boolean asBoolean() method

class Predicate {
    boolean value
    boolean asBoolean() { value }
}

def tr uePred  = new Predicate(value: true)
def fals ePred = new Predicate(value: false)

assert truePred && !falsePred


SQL support reﬁnements
// batch statements
sql.withBatch { stmt ‐>
e ‐>
["Paul", "Jochen", "Guillaume"].each { nam e)"
stmt.addBat ch "insert into PERSON (name) values ($nam
}
}

// transaction support
def persons = sql.dataSet("person")
sql.withTransaction {
  persons.add name: "Paul"
  persons.add name: "Jochen"
  persons.add name: "Guillaume"
  persons.add name: "Roshan"
}


Groovy 1.7.x changes

Groovy 1.7.1 and 1.7.2 have been released
Groovy 1.7.3 is coming soon

Here’s what’s new!


Map improvements
// map auto‐vification
def m = [:].withDefault { key ‐> "Default" }
assert m['z'] == "Default"
assert m['a'] == "Default"

// default sort
m.sort()

// sort with a comparator
m.sort({ a, b ‐> a <=> b } as Comparator)


XML back to String
Ability to retrieve the XML string from a node
from an XmlSlurper GPathResult
def xml = """
<books>
<book isbn="12345">Groovy in Action</book>
</books>
"""
def root = new XmlSlurper().parseText(xml)
def someNode = root.book
def bu ilder = new StreamingMarkupBuilder()

assert build er.bindNode(someNode).toString() ==
"<book isbn='12345'>Groovy in Action</book>"


Currying improvements
// right currying
def divide = { a, b ‐> a / b }
def halver = divide.rcurry(2)
assert halver(8) == 4

// currying n‐th parameter
def jo inWithSeparator = { one, sep, two ‐>
one + sep + two
}
def joinWithComma =
jo inWithSeparator.ncurry(1, ', ')
assert joinWithComma('a', 'b') == 'a, b'


New icon for the Swing console


New String methods
println """ println """
    def method() {     |def method() {
        return 'bar'     |    return 'bar'
    }     |}
""".stripIndent() """.stripMargin('|')

// string "translation" (UNIX tr)
assert 'hello'.tr('z‐a', 'Z‐A') == 'HELLO'
WAAAA!'
asse rt 'Hello World!'.tr('a‐z', 'A') == 'HAAAA
2d!'
assert 'Hell o World!'.tr('lloo', '1234') == 'He224 W4r

// capitalize the first letter
assert 'h'.capitalize() == 'H'
assert 'hello'.capitalize() == 'Hello'
rld'
asse rt 'hello world'.capitalize() == 'Hello wo
mmand)
// tab/space (un)expansion (UNIX expand co
7 8        '
assert '1234567t8t '.expand() == '123456
'
assert '    x    '.unexpand() == '    xt


...and beyond!

Groovy 1.8 & beyond
Still subject to discussion
Always evolving roadmap
Things may change!


What’s cooking?

What we’re working on
More runtime performance improvements
Closure annotations
Gradle build
Modularizing Groovy
Align with JDK 7 / Java 7 / Project Coin
Enhanced DSL support
AST Templates
Towards MOP 2


«Blackdrag»
revealed
the black magic!


Closure annotations
Groovy 1.5 brought Java 5 annotations
What if... we could go beyond what Java offered?
In 1.7, we can put annotations on packages, imports and
variable declarations
But annotations are still limited in terms of parameters
they allow

Here comes closure annotations!
Groovy 1.8 will give us the ability to access annotation
with closure parameters at runtime


GContracts
Closures are already allowed in the Groovy 1.7
Antlr grammar
Andre Steingreß created GContracts,
a «design by contract» module
// a class invariant
@I nvariant({ name.size() > 0 && age > ageLimit() })

// a method pre‐condition
@Requires({ message != null })

// a method post‐condition
@Ensures({ returnResult % 2 == 0 })


bu ild
dh oc oo vy
ore a lar Gr
M du s!
o
e m rom H an
Mor ef
M or


More modular build
«Not everybody needs everything!» ™

A lighter Groovy-core
what’s in groovy-all?

Modules
test, jmx, swing, xml, sql, web, template
integration (bsf, jsr-223)
tools (groovydoc, groovyc, shell, console, java2groovy)


Java 7 / JDK 7 / Project Coin
JSR-292 InvokeDynamic
Simple Closures?
Proposals from Project Coin
Strings in switch
Automatic Resource Management
Improved generics type inference (diamond <>)
Simpliﬁed varargs method invocation
Better integral literals
Language support for collections


Improved DSL support

GEP-3: an extended command expression DSL
Groovy Extension Proposal #3
A Google Summer of Code student will work on that

Command expressions
basically top-level statements without parens
combine named and non-named arguments in the mix
for nicer Domain-Speciﬁc Languages


Before GEP-3
The idea: extend command-expressions, beyond
top-level statements, for chained method calls
Before
send("Hello").to("Jochen")
send("Hello", from: "Guillaume").to("Jochen")

sell(100.shares).of(MSFT)

take(2.pills).of(chloroquinine).in(6.hours)

every(10.minutes).execute { }

given { }.when { }.then { }

blend(red, green).of(acrylic)


With GEP-3
After
send "Hello"  to "Jochen"
send "Hello", from: "Guillaume"  to "Jochen"

sell 100.shares  of MSFT

take 2.pills  of chloroquinine  in 6.hours

every 10.minutes  execute {  }

given { } when { } then { }

blend red, green  of acrylic


With GEP-3
After
send "Hello"  to "Jochen"
send "Hello", from: "Guillaume"  to "Jochen"

sell 100.shares  of MSFT
Less
pare
take 2.pills  of chloroquinine  in 6.hours
& co ns
every 10.minutes  execute {  }
mm
given { } when { } then { } as
blend red, green  of acrylic


AST Templates
Since AST, it’s easier to write AST Transformations
But we can even do better!

Hamlet D’Arcy is working on a new proposal
GEP-4 — AST Templates


a new
MOP


Towards a new MOP?
The Meta-Object Protocol show its age
different stratiﬁcation layers
DGM, categories, custom MetaClasses, ExpandoMetaClass...
different characteristics
scope: global, local, thread-bound
works across the hierarchy or not
A better MOP could...
help for performance
offer more granularity
let the developer choose the characteristics he needs
provide a layered approach of changes


Some potential modules
GPars was considered a potential module for
addition into core
but got a life of its own!

Parser combinators
for when you hit the walls of the Groovy syntax
and AST transformations won’t cut it

Pattern matching


Summary (1/2)
No need to wait for Java 7, 8, 9...
closures, properties, interpolated strings, extended
annotations, metaprogramming, [YOU NAME IT]...


Summary (1/2)
No need to wait for Java 7, 8, 9...
closures, properties, interpolated strings, extended
annotations, metaprogramming, [YOU NAME IT]...

oov y’s
Gr ive
no vat
sti ll in
20 03!
si nce


Summary (2/2)
But it’s more than just a language, it’s a very rich
and active ecosystem!
Grails, Griffon, Gradle, GPars, Spock, Gaelyk...


Thanks for your attention!

e
aforg pment
ume L Develo
Guilla Groovy om
He ad of e@ gmail.c
glaforg rge
Email: @glafo
:
Twitter


Questions & Answers


Images used in this presentation
House / past: http://www.flickr.com/photos/jasonepowell/3680030831/sizes/o/
Present clock: http://www.flickr.com/photos/38629278@N04/3784344944/sizes/o/
Future: http://www.flickr.com/photos/befuddledsenses/2904000882/sizes/l/
Cooking: http://www.flickr.com/photos/eole/449958332/sizes/l/
Black dragon: http://www.free-computer-wallpapers.com/pictures/Fantasy-wallpaper/Black_Dragon
Puzzle: http://www.everystockphoto.com/photo.php?imageId=263521
Light bulb: https://newsline.llnl.gov/retooling/mar/03.28.08_images/lightBulb.png
Spock: http://altoladeira.files.wordpress.com/2009/07/spock2.jpg


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