Groovy: to Infinity and Beyond -- JavaOne 2010 -- Guillaume Laforge

Guillaume Laforge

• Groovy Project Manager
• JSR-241 Spec Lead
• Head of Groovy Development
at SpringSource
• Initiator of the Grails framework

• Co-author of Groovy in Action

• Speaker: JavaOne, QCon, JavaZone, Sun TechDays,
Devoxx, The Spring Experience, SpringOne, JAX,
Dynamic Language World, IJTC, and more...

Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 2

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


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 (bool) 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 */ })

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



AIC and NC


Fo rJ ava
’n p aste
c opy
atib ility
co mp
s ake :-)


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


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

• Since Groovy 1.7.0, Groovy 1.7.1, 1.7.2, 1.7.3,
1.7.4 and 1.7.5 have been released already!

• 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 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 


Groovy 1.8 & beyond

• Still subject to discussion
• Always evolving roadmap
• Things may change!


What we’re working on

• More runtime performance improvements
• Closure annotation parameters
• Closure composition
• New AST transformations
• Gradle build
• Modularizing Groovy
• Align with JDK 7 / Java 7 / Project Coin
• Enhanced DSL support
• AST Templates


Closure annotation parameters

• 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 annotation parameters!
– 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
– André 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 })


Closure composition

• Functional flavor!

def plus2  = { it + 2 }
def times3 = { it * 3 }
 
def composed1 = plus2 << times3
assert composed1(3) == 11
assert composed1(4) == plus2(times3(4))
 
def composed2 = times3 << plus2
assert composed2(3) == 15
assert composed2(5) == times3(plus2(5))
 
// reverse composition
assert composed1(3) == (times3 >> plus2)(3)


build
dh oc oo vy
or e a lar Gr
M o du Hans!
or e m rom
M 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 (or 8?) / 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

• Command expressions
– basically top-level statements without parens
– combine named and non-named arguments in the mix
•for nicer Domain-Specific Languages
– (methodName arguments )*


Before GEP-3

• The idea: extend command-expressions, beyond
top-level statements, for chained method calls
• Before

send("Hello").to("Graeme")

check(that: margherita).tastes(good)

sell(100.shares).of(MSFT)

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

wait(10.minutes).and(execute {  })

blend(red, green).of(acrylic)


With GEP-3

• After

send "Hello"  to "Graeme"

check that: margherita  tastes good

sell 100.shares  of MSFT

take 2.pills  of chloroquinine  after 6.hours

wait 10.minutes  and execute {  }

blend red, green  of acrylic


With GEP-3

• After
Less
& co pare
ns
send "Hello"  to "Graeme"

check that: margherita  tastes good mm
sell 100.shares  of MSFT
as
take 2.pills  of chloroquinine  after 6.hours

wait 10.minutes  and execute {  }

blend red, green  of acrylic


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]...

’s s till
Gro ovy
ova tive
inn
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
e Laforg velopment
Gui llaum ovy De m
of Gro e@gmail.co
Head laforg
g
Email: @glaforge
r:
Twitte


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/
• Puzzle: http://www.everystockphoto.com/photo.php?imageId=263521
• Light bulb: https://newsline.llnl.gov/retooling/mar/03.28.08_images/lightBulb.png


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