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Groovy overview, DSLs and ecosystem - Mars JUG - 2010
 

Groovy overview, DSLs and ecosystem - Mars JUG - 2010

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Groovy overview, DSLs and ecosystem - Mars JUG - 2010 Groovy overview, DSLs and ecosystem - Mars JUG - 2010 Presentation Transcript

  • Groovy Overview, DSLs, ecosystem Presentation given for the Mars JUG by Guillaume Laforge Groovy Project Manager Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited.
  • Guillaume Laforge • Groovy Project Manager • JSR-241 Spec Lead • Head of Groovy Development at SpringSource / VMWare • Initiator of the Grails framework • Co-author of Groovy in Action • Member of @lescastcodeurs • 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
  • Contact information • Email – glaforge@gmail.com • Twitter – @glaforge • Blog – http://glaforge.free.fr/blog/groovy • Groovy mailing-lists – http://old.nabble.com/codehaus---Groovy-f11866.html Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 3
  • A little story Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 4
  • nd a Ag e • Introduction to Groovy – syntax basics – useful APIs • Domain-Specific Languages • Rich ecosystem Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 5
  • nd a Ag e • Introduction to Groovy Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 6
  • Groovy in a few words • Groovy is a dynamic language for the JVM – with a Meta Object Protocol – compiles directly to bytecode – provides seamless Java interoperability • Groovy was created in 2003, is hosted at Codehaus, and is under the Apache license • Relaxed grammar deriving from Java 5 – annotations, generics, static imports, enums, varargs... – borrowed good ideas from Ruby, Python, Smalltalk –flat learning curve for Java developers Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 7
  • Most popular alternative language for the JVM • In terms of... – Poll and survey popularity – Books available on the shelves – Jobs on the job boards – Integration in other products – Download numbers – Community activity – Innovation Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 8
  • In terms of polls & surveys Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 9
  • In terms of books Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 10
  • In terms of jobs Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 11
  • In terms of integration in other projects and products • Groovy is integrated in many Open Source projects and Commercial products – Spring, IntelliJ IDEA, SAP Composition on Grails, RIFE, Mule ESB, Apache Camel, eXo Platform, SOAP UI, JBoss SEAM, XWiki, Oracle OC4J, SpringSource tcServer, Oracle Data Integrator, Canoo WebTest, Oracle Busines Components, IBM WebSphere sMash, CodeStreet MarketData Works, SpringSource Hyperic HQ – Mutual of Omaha, US National Cancer Institute, Patterson Institute for Cancer Research, IRSN... • and certainly many more I’ve forgotten! Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 12
  • In terms of download numbers • Number of downloads per month – 2003: a few hundreds – 2005: ~5k – 2008: ~35k – 2009: ~70k • Add to that number – all the integrations... – all the artifacts downloads from Maven’s repository! • Highly successful OSS project! Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 13
  • In terms of community activity • Very high traffic on the mailing-lists – 1500+ members • Dedicated conferences – Groovy Grails eXchange – SpringOne 2GX – GR8 Conference (Europe / USA) – Excellent coverage of Groovy and Grails at all major conferences around the world • Dedicated podcast – GrailsPodcast • Dedicated online PDF magazine – GroovyMag Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 14
  • In terms of innovation • JAX Innovation Award – Biggest German Java conference • Groovy won first prize in 2007 – Grails scored second in 2008 – Spring arrived first in 2006 Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 15
  • Features at a glance • Fully Object-Oriented: same as Java • Closures: reusable/assignable code blocks • Properties: no more boring getters/setters • Optional typing: your choice! • Various shortcut notations: native syntax for lists, maps, ranges, regex... • Handy wrapper APIs: XML, JDBC, template engine, Swing UIs, collection methods... • Strong ability for authoring DSLs • A rich and lively ecosystem of additional modules Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 16
  • Mandatory Hello World • Java public class HelloWorld { private String name; style... public String getName() { return name; } public void setName(String name) { this.name = name; } public String greet() { return "Hello " + name; } ) { public static void main(String[] args ld(); HelloWorld helloWorld = new HelloWor helloWorld.setName("Groovy"); )); System.out.println(helloWorld.greet( } } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 17
  • Mandatory Hello World • Groovy public class HelloWorld { private String name; style... public String getName() { return name; } public void setName(String name) { this.name = name; } public String greet() { return "Hello " + name; } ) { public static void main(String[] args ld(); HelloWorld helloWorld = new HelloWor helloWorld.setName("Groovy"); )); System.out.println(helloWorld.greet( } } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 18
  • Mandatory Hello World • Groovy style... class HelloWorld { String name String greet() { "Hello $name" } } def helloWorld = new HelloWorld(name: "Groovy") println helloWorld.greet() Take 2! Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 19
  • Syntax basics • Grammar deriving from Java 5 – annotations, enums, static imports, generics... • Usual Java keywords, control structures... • Same APIs – strings, collections, regex, security, threading... • Same Object Orientation – No impedance mismatch! – Flat learning curve for Java developers! • But offers additional native syntax constructs Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 20
  • On Java interoperability • Groovy is the alternative JVM language providing the best integration with Java JInterface GInterface <<implements>> <<implements>> • Mix and match Groovy and Java GClass JClass – even with a cyclic language dependency JClass GClass • Groovy comes with a «joint compiler» – compiling Groovy as Java stubs – calling the Javac compiler – compiling the Groovy classes • Excellent IDE support (Eclipse/IntelliJ/NetBeans) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 21
  • Native syntax constructs • Lists def someNumbers = [1, 2, 3, 5, 7, 11] • Ranges def range = 1..18 • Maps def states = [CA: ‘California’, TX: ‘Texas’] • Regular expressions ~/fo*/ ‘foo’ =~ /fo*/ ‘foo’ ==~ /fo*/ Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 22
  • GStrings • Sexiest feature of the language! • Ability to embed variables inside strings def firstname = "Guillaume" def lastname = "${firstname} Laforge" e" assert lastname == "Guillaume Laforg def date = "Today is: ${new Date()}" def multiline = """Hello, How are you?""" Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 23
  • Closures • A reusable / assignable code block – CS 101 for a proper definition } def helloPrinter = { println "hello" helloPrinter() def twice = { it * 2 } assert twice(3) == 6 assert twice('foo') == 'foofoo' def mult = { int a, int b -> a * b } def multBy5 = mult.curry(5) assert multBy5(4) == 20 def apply(closure) { closure() } apply { /* do something */ } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 24
  • Time savers • The «Groovy Truth» def blank = ""; assert !blank def empty = []; assert !empty • Safe graph navigation def order = null assert order?.customer?.address == null • Elvis operator def na me = customer.name ?: "Unknown" Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 25
  • GDK: Groovy Development Kit • Thanks to Groovy’s dynamic nature, we «decorate» existing JDK classes to add new handy methods – we can’t extend java.io.File or java.lang.String, can we? n it } new File("apache.log").eachLine { printl (1..100).findAll { it % 2 == 1 } speakers.groupBy { it.lastname } "123".padLeft(5, '0') "ls -la".execute() ) "R3Jvb3Z5IHJvY2tzIQ==".decodeBase64( Th read.start { /* code to execute */ } • Add your own extensions! Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 26
  • Now onto APIs! • After this language crash course, let’s have a look at the APIs Groovy provides: – Markup builders and slurpers – Swing builder – Template engine – JDBC facilities – JMX builder – Ant scripting Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 27
  • Markup builder • Producing markup content new MarkupBuilder().languages { language(name: "Groovy") { feature(coolness: "low", "SQL") ) feature(coolness: "high", "Template" } language(name: "Perl") } • Will yield <languages> <language name = "Groovy"> <feature coolness="low">SQL</feature> ature> <feature coolness="high">Template</fe </language> <language name: "Perl"/> </languages> Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 28
  • XML slurper • Easily parsing and consumming XML content • Navigating through the nodes as an object graph def xml = """ <languages> <language name="Groovy"> <feature coolness="low">SQL</feature> ature> <feature coolness="high">Template</fe </language> <language name="Perl"/> </languages>""" (xml) def root = new XmlSlurper().parseText t() println root.language.feature[1].tex ] == "low" } root.lan guage.feature.findAll{ it['@coolness' .each{ println it.text() } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 29
  • Swing builder • Creating Swing UI with a programmatic descriptive Domain-Specific Language import groovy.swing.SwingBuilder import java.awt.BorderLayout as BL def count = 0 new SwingBuilder().edt { ow: true) { fram e(title: 'Frame', size: [300,300], sh borderLayout() tton!", textlabel = label(text: "Click the bu constraints: BL.NORTH) button(text: 'Click Me', actionPerformed: { count++ me(s)." textlabel.text = "Clicked ${count} ti println "clicked"}, constraints:BL.SOUTH) } } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 30
  • Template engine • Templating capabilities, with embedded GStrings, and scriptlet notation ne import groovy.text.SimpleTemplateEngi def text = ''' Dear <%= firstname %> %>. So nice to meet you in <% print city ${signed}''' e", def binding = [fir stname: "Guillaume", city: "The Hagu signed: "MrG"] () def engine = new SimpleTemplateEngine ke(binding) temp late = engine.createTemplate(text).ma • A template servlet also exists Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 32
  • JDBC facilities • Transparent resource handling thanks to closures ) def sql = Sql.newInstance(url, usr, pwd, driverar)") sql.execut e("insert into table values ($foo, $b, b]) , [a sql.ex ecute("insert into table values(?,?)" .name } it sql.ea chRow("select * from USER") { print ER") def list = sql.rows("select * from US • A poorman’s dataset notion def set = sql.dataSet("USER") set.add(name: "Johnny", age: 33) ame } set.each { user -> println user.n 42 } se t.findAll { it.age > 22 && it.age < Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 33
  • JMX Builder • Expose, configure JMX beans, export operations, create timers, event handling with closures, and more... def jmx = new JmxBuilder() def beans = jmx.export { bean(new CpuLoadMonitor()) bean(new DiskOccupationMonitor()) } • You could easily monitor your Spring application’s exposed JMX beans through some Groovy script! Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 34
  • Ant builder • Script and reuse any Ant task – FTP, SSH, Javac, file handling, etc. new AntBuilder().sequential { def buildClasses = "build/classes" // create classes directory mkdir dir: buildClasses // compile sources lasses javac srcdir: "src", destdir: buildC // jar everything dClasses jar destfile: "my.jar", basedir: buil } • Used in Gant and Gradle Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 35
  • Grape: a great way for sharing Groovy scripts • Grape: Groovy Advanced Packagning Engine • You can «grab» dependencies in your scripts – first run will download the dependencies – next runs, the dependencies will be found in the ivy cache on your system jdk15") @Grab("net.sf.json-lib:json-lib:2.3: import net.sf.json.groovy.* assert new JsonSlurper().parseText( new JsonGroovyBuilder().json { aume") book(title : "Groovy in Action", author: "Guill }.toString() ).book.title == "Groovy in Action" Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 36
  • Benefits of the Groovy APIs • Easily share scripts thanks to Grape – no need to package JARs –automate all repetitive tasks with Ant builder • Simple to create reports or generate code with markup builders or template engines • You can migrate / inject / modify data with the SQL facilities accessing your database through JDBC • Create simple Swing UIs to interact with backends • You can monitor server farms through JMX builder Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 37
  • Spring integration (1/2) •Groovy integrated in Spring since 2.0 –ability to define beans in Groovy –to monitor changes of Groovy beans on the filesystem –to modify the behaviour of Groovy scripts and beans –to inline Groovy scripts with <lang:inline-script> <lang:groovy id="messenger" refresh-check-delay="5000" roovy"> script-source="classpath:Messenger.g "Hi" /> <lang:property name="message" value= </lang:groovy> BookingService"> <bean id ="bookingService" class="x.y.Default nger" /> <property name="messenger" ref="messe </bean> Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 38
  • Spring integration (2/2) • Grails provides a Spring bean builder – for programmatically define Spring configurations – more flexible than pure XML declarative descriptions ) de f bb = new grails.spring.BeanBuilder( bb.beans { adder(AdderImpl) calcBean(CalcImpl) } t() def ctx == bb.createApplicationContex def calc = ctx.getBean(‘calcBean’) println calc.doAdd(3, 4) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 39
  • Question & Answers Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 40
  • nd a Ag e • Domain-Specific Languages Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 41
  • The Context
  • Subject Matter Expers, Business Analysts...
  • Developer producing LOLCODE HAI CAN HAS STDIO? I HAS A VAR IM IN YR LOOP UP VAR!!1 VISIBLE VAR IZ VAR BIGGER THAN 10? KTHXBYE IM OUTTA YR LOOP KTHXBYE
  • Lots of Languages...
  • And in the end... nobody understands each other
  • Expressing Requirements... Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 47
  • DSL: a potential solution? •Use a more expressive language than a general purpose one •Share a common metaphore of understanding between developers and subject matter experts •Have domain experts help with the design of the business logic of an application •Avoid cluttering business code with too much boilerplate technical code •Cleanly separate business logic from application code •Let business rules have their own lifecycle Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 48
  • Towards more readibility (1) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 49
  • Towards more readibility (1) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 49
  • Towards more readibility (1) 20% Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 49
  • Towards more readibility (2) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 50
  • Towards more readibility (2) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 50
  • Towards more readibility (2) 80% Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 50
  • A collection of DSLs • In our everyday life, we’re surrounded by DSLs – Technical dialects – Notations – Business languages Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 51
  • Technical dialects Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 52
  • SQL
  • ^[w-.]+@([w-]){2,4}$ Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 54
  • Notations Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 55
  • 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6
  • L2 U F-1 B L2 F B -1 U L2
  • Visual!
  • Real-life Groovy examples • Anti-malaria drug resistance simulation • Human Resources employee skills representation • Insurance policies risk calculation engine • Loan acceptance rules engine for a financial platform • Mathematica-like lingua for nuclear safety simulations • Market data feeds evolution scenarios • and more... Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 59
  • Three levels of techniques Flexible & Meta- AST malleable syntax programming transformations • scripts • POGO • AST traversal • optional typing • categories • local • native syntax • builders transformations constructs • custom MetaClass • global • parens / semi • ExpandoMetaClass transformations ommission • hooks into Antlr • named arguments • BigDecimal • operator overloading • closures Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 60
  • A flexible & malleable syntax • No need to write full-blown classes, use scripts • Optional typing (def) – in scripts, you can even omit the def keyword • Native syntax constructs • Parentheses & semi-colons are optional • Named arguments • BigDecimal by default for decimal numbers • Closures for custom control structures • Operator overloading Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 61
  • Scripts vs classes • Hide all the boilerplate technical code – an end-user doesn’t need to know about classes – public class Rule { public static void main(String[] args) { System.out.println(“Hello”); } } – println “Hello” Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 62
  • Optional typing • No need to bother with types or even generics – unless you want to! • Imagine an interest rate lookup table method returning some generified type: –Rate<LoanType, Duration, BigDecimal>[] lookupTable() { ... } def table = lookupTable() • No need to repeat the horrible generics type info! Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 63
  • Native syntax constructs • Lists – [Monday, Tuesday, Wednesday] • Maps – [CA: ‘California’, TX: ‘Texas’] • Ranges – def bizDays = Monday..Friday – def allowedAge = 18..65 – You can create your own custom ranges Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 64
  • Optional parens & semis • Make statements and expressions look more like natural languages – move(left); – move left Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 65
  • Named arguments • In Groovy you can mix named and unnamed arguments for method parameters – named params are actually put in a map parameter – plus optional parens & semis • take 1.pill, of: Chloroquinine, after: 6.hours • Corresponds to a method signature like: – def take(Map m, MedicineQuantity mq) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 66
  • BigDecimal by default • Main reason why financial institutions often decide to use Groovy for their business rules! – Although these days rounding issues are overrated! • Java vs Groovy for a simple interpolation equation • BigDecimal uMinusv = c.subtract(a); BigDecimal vMinusl = b.subtract(c); BigDecimal uMinusl = a.subtract(b); return e.multiply(uMinusv) .add(d.multiply(vMinusl)) .divide(uMinusl, 10, BigDecimal.ROUND_HALF_UP); • (d * (b - c) + e * (c - a)) / (a - b) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 67
  • Custom control structures, thanks to closures • When closures are last, they can be put “out” of the parentheses surrounding parameters • unless (account.balance > 100.euros, { account.debit 100.euros }) • unless (account.balance > 100.euros) { account.debit 100.euros } • Signature def unless(boolean b, Closure c) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 68
  • Operator overloading a + b a - b a.plus(b) a.minus(b) • Currency amounts a * b a.multiply(b) – 15.euros + 10.dollars a / b a.divide(b) a % b a.modulo(b) • Distance handling a ** b a.power(b) – 10.kilometers - 10.meters a | b a.or(b) a & b a.and(b) • Workflow, concurrency a ^ b a.xor(b) a[b] a.getAt(b) – taskA | taskB & taskC a << b a.leftShift(b) a >> b a.rightShift(b) • Credit an account +a a.unaryPlus() – account << 10.dollars -a a.unaryMinus() account += 10.dollars ~a a.bitwiseNegate() account.credit 10.dollars Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 69
  • The MOP (Meta-Object Protocol)
  • Groovy’s MOP • All the accesses to methods, properties, constructors, operators, etc. can be intercepted thanks to the MOP • While Java’s behavior is hard-wired at compile- time in the class • Groovy’s runtime behavior is adaptable at runtime through the metaclass • Different hooks for changing the runtime behavior – GroovyObject, custom MetaClass implementation, categories, ExpandoMetaClass Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 71
  • GroovyObject • All instances of classes created in Groovy implement the GroovyObject interface: –get/setProperty(String name) –invokeMethod( String name, Object[] params) –propertyMissing(String name) –methodMissing( String name, Object[] params) –get/setMetaClass(MetaClass mc) • A GO can have “pretended” methods and properties Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 72
  • MetaClass • The core of Groovy’s MOP system –invokeConstructor() –invokeMethod() and invokeStaticMethod() –invokeMissingMethod() –getProperty() and setProperty() –getAttribute() and setAttribute() –respondsTo() and hasProperty() • MetaClasses can change the behavior of existing third-party classes — even from the JDK Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 73
  • ExpandoMetaClass • A DSL for MetaClasses! • MoneyAmount.metaClass.constructor = { ... } Number.metaClass.getDollars = { ... } Distance.metaClass.toMeters = { ... } Distance.metaClass.static.create = { ... } • To avoid repetition of Type.metaClass, you can pass a closure to metaClass { ... } • The delegate variable in closure represents the current instance, and it the default parameter Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 74
  • The Builder pattern
  • A builder for HR • softskills { ideas { capture 2 formulate 3 } ... } knowhow { languages { java 4 groovy 5 } ... } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 76
  • A builder for HR • softskills { ideas { capture 2 formulate 3 } ... } knowhow { languages { java 4 groovy 5 } ... } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 76
  • Builders • Builders are... – a mechanism for creating any tree-structered graph – the realization of the GoF builder pattern at the syntax level in Groovy – simply a clever use of chained method invocation, closures, parentheses omission, and use of the GroovyObject methods • Existing builders – XML, Object graph, Swing, Ant, JMX, and more... Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 77
  • The clever trick • GroovyObject#invokeMethod() is used to catch all non-existing method calls in the context of the builder • The nesting of closures visually shows the level of nesting / depth in the tree • builder.m1(attr1:1, attr2:2, { builder.m2(..., {...}) } becomes equivalent to builder.m1(attr1:1, attr2:2) { m2(...) {...} } thanks to parens omission Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 78
  • Adding properties to numbers • Three possible approaches – create a Category •a category is a kind of decorator for default MCs – create a custom MetaClass •a full-blown MC class to implement and to set on the POGO instance – use ExpandoMetaClass •friendlier DSL approach but with a catch Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 79
  • With a Category • class DistanceCategory { static Distance getMeters(Integer self) { new Distance(self, Unit.METERS) } } use(DistanceCategory) { 100.meters } • Interesting scope: thread-bound & lexical • Have to surround with “use” – but there are ways to hide it Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 80
  • With an ExpandoMetaClass • Number.metaClass.getMeters = {-> new Distance(delegate, Unit.METERS) } 100.meters • Works for the class hierarchy for POJOs, and a flag exists to make it work for POGOs too • But the catch is it’s really a global change, so beware EMC enhancements collisions Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 81
  • Compile-time metaprogramming • Groovy 1.6 introduced AST Transformations • Compile-time == No runtime performance penalty! Transformation Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 82
  • Compile-time metaprogramming • With metaprogramming, Groovy’s able to modify the behaviour of programs... at runtime • Groovy 1.6 introduced AST Transformations – AST: Abstract Syntax Tree – Ability to change what’s being compiled at compile-time! •No runtime impact! •Lets you change the semantics of your programs! •Nice way of implementing patterns and removing boiler- plate technical code • Two kinds of transformations: global and local Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 83
  • AST Transformations • Two kinds of transformations – Global transformations •applicable to all compilation units – Local transformations •applicable to marked program elements •using specific marker annotations Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 84
  • AST Transformations in Groovy 1.6 • Several (local) transformations finds their way – @Singleton — okay, not really a pattern :-) – @Immutable, @Lazy, @Delegate – @Newify – @Category and @Mixin – @PackageScope – Swing’s @Bindable and @Vetoable – Grape’s @Grab • Let’s have a look at some of them Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 85
  • The @Singleton anti-pattern •The evil Java singleton public class Evil { new Evil(); public static final Evil instance = privavte Evil() {} ; } Evil getInstance() { return instance } •In Groovy now: @Singleton class Evil {} •A lazy version also: @Singleton(lazy = true) class Evil {} Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 86
  • @Immutable • To properly implement immutable classes – No mutators (state musn’t change) – Private final fields – Defensive copying of mutable components – Proper equals() / hashCode() / toString() for comparisons, or for keys in maps, etc. @I mmutable class Coordinates { Double lat, lng } 5) def c1 = new Coordinates(lat: 48.8, lng: 2. de f c2 = new Coordinates(48.8, 2.5) assert c1 == c2 Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 87
  • @Lazy, not just for lazy dudes! • When you need to lazily evaluate or instantiate complex data structures for class fields, mark them with the @Lazy annotation class Dude { @Lazy pets = retrieveFromSlowDB() } • Groovy will handle the boiler-plate code for you! Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 88
  • @Delegate Not just for managers! •You can delegate to fields of your class –Think multiple inheritance class Employee { def doTheWork() { "done" } } class Manager { @Deleg ate Employee slave = new Employee() } def god = new Manager() assert god.doTheWork() == "done" •Damn manager will get all the praise... Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 89
  • Global transformations • Implement ASTTransformation • Annotate the transfo specifying a compilation phase • @GroovyASTTransformation(phase=CompilePhase.CONVERSION) public class MyTransformation implements ASTTransformation { public void visit(ASTNode[] nodes, SourceUnit unit) { ... } } • For discovery, create the file META-INF/services/ org.codehaus.groovy.transform.ASTTransformation • Add the fully qualified name of the class in that file Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 90
  • Local transformations • Same approach as Globale transformations • But you don’t need the META-INF file • Instead create an annotation to specify on which element the transformation should apply @Retention(RetentionPolicy.SOURCE) @Target([ElementType.METHOD]) @GroovyASTTransformationClass( ["fqn.MyTransformation"]) public @interface WithLogging {...} Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 91
  • Example: the Spock framework • Changing the semantics of the original code • But keeping a valid Groovy syntax @Speck class HelloSpock { to?"() { def "can you figure out what I'm up expect: name.size() == size where: name | size "Kirk" | 4 "Spock" | 5 "Scotty" | 6 } } • Check out http://www.spockframework.org Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 92
  • Various integration mechanisms • Java 6’s javax.script.* APIs (aka JSR-223) • Spring’s language namespace • Groovy’s own mechanisms • But a key idea is to externalize those DSL programs – DSL programs can have their own lifecycle – no need to redeploy an application because of a rule change – business people won’t see the technical code Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 93
  • Java 6’s javax.script.* API • Groovy 1.6 provides its own implementation of the javax.script.* API • ScriptEngineManager mgr = new ScriptEngineManager(); ScriptEngine engine = mgr.getEngineByName(“Groovy”); String result = (String)engine.eval(“2+3”); Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 94
  • Spring’s lang namespace • POGOs (Plain Old Groovy Objects) can be pre- compiled as any POJO and used interchangeably with POJOs in a Spring application • But Groovy scripts & classes can be loaded at runtime through the <lang:groovy/> namespace and tag • Reloadable on change • Customizable through a custom MetaClass • <lang:groovy id="events" script-source="classpath:dsl/eventsChart.groovy" customizer-ref="eventsMetaClass" /> Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 95
  • Groovy’s own mechanisms • Eval – for evaluating simple expressions • GroovyShell – for more complex scripts and DSLs • GroovyClassLoader – the most powerful mechanism Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 96
  • Eval • Simple mechanism to evaluate math-like formulas • Eval.me ( ‘3*4’) Eval.x (1, ‘3*x + 4’) Eval.xy (1, 2, ‘x + y’) Eval.xyz(1, 2, 3, ‘x * y - z’) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 97
  • GroovyShell • A Binding provides a context of execution – can implement lazy evaluation if needed • A base script class can be specified • def binding = new Binding() binding.mass = 22.3 binding.velocity = 10.6 def shell = new GroovyShell(binding) shell.evaluate(“mass * velocity ** 2 / 2”) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 98
  • GroovyClassLoader • Most powerful mechanism – could also visit or change the AST – scripts & classes can be loaded from elsewhere – more control on compilation • GroovyClassLoader gcl = new GroovyClassLoader(); Class clazz = gcl.parseClass( new File(“f.groovy”)); GroovyObject instance = (GroovyObject)clazz.newInstance(); instance.setMetaClass(customMC); Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 99
  • Externalize business rules • Although Groovy DSLs can be embedded in normal Groovy classes, you should externalize them • Store them elsewhere – in a database, an XML file, etc. • Benefits – Business rules are not entangled in technical application code – Business rules can have their own lifecycle, without requiring application redeployments Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 100
  • A few considerations Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 101
  • Start small, with key concepts Beware over-engineering!
  • Grow your language progressively
  • Get your hands dirty Play with the end-users
  • Let your DSL fly, it’s not yours, it’s theirs!
  • Tight feedback loop Iterative process
  • Stay humble, You can’t get it right the 1st time. Don’t design alone at your desk Involve the end users from the start
  • Playing it safe in a sandbox
  • Various levels of sandboxing • Groovy supports the usual Java Security Managers • Use metaprogramming tricks to prevent calling / instanciating certain classes • Create a special GroovyClassLoader AST code visitor to filter only the nodes of the AST you want to keep – ArithmeticShell in Groovy’s samples Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 109
  • Test, test, test! • Don’t just test for nominal cases – Explicitely test for errors! • Ensure end-users get meaninful error messages Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 110
  • Question & Answers Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 111
  • nd a Ag e • The Groovy Ecosystem Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 112
  • The Groovy Ecosystem • Many projects based on Groovy • Serve various purposes: – build applications (ie. frameworks) •Grails (web apps), Gaelyk (Google App Engine), Griffon (Swing apps) – enhanced testing •Easyb (BDD), Spock, Gmock (mocking), SoapUI (WS) – help building projects •Gant (ant sugar), Gradle (adhoc build system) – web services interaction •HTTPBuilder (REST), GroovyWS (SOAP) Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 113
  • Gaelyk •Groovy on Google App Engine – Lightweight Groovy tooking for writing applications in Groovy on GAE/J – Leverages Groovlets and Groovy’s template engine – http://gaelyk.appspot.com • Groovy Web Console – http://groovyconsole.appspot.com Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 114
  • GPars • Actors, dataflow, concurrency, and more – for harnessing our multicore platforms • GPars web site: – http://gpars.codehaus.org Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 115
  • Easyb (1/4) • From the website: – « Easyb is a behavior driven development (BDD) framework for the Java platform. By using a specification based Domain-Specific Language, Easyb aims to enable executable, yet readable documentation » • Write specifications in Groovy • Run them from CLI, Maven, or Ant – provides various report formats • BDD == given/when/then paradigm Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 116
  • Easyb (2/4) • First, let’s write a story given "an invalid zip code" itialized" and "given the zipcodevalidator is in lid zip code" wh en "validate is invoked with the inva return false" then "the validator instance should Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 117
  • Easyb (3/4) • Let’s write the test itself given "an invalid zip code", { invalidzipcode = "221o1" } d", { and "giv en the zipcodevalidator is initialize zipvalidate = new ZipCodeValidator() } p code", { when "val idate is invoked with the invalid zi pcode) va lue = zipvalidate.validate(invalidzi } e", { then "the validator instance should return fals value.shouldBe false } • Afterwards, write the code that make the test pass Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 118
  • Easyb (4/4) • There’s also the specification format instance", { before "initialize zipcodevalidator ; zipvalidate = new ZipCodeValidator() } { it "should deny invalid zip codes", zip -> [" 221o1", "2210", "22010-121o"].each { zipvalidate.validate(zip).is false } } { it "should accept valid zip codes", { zip -> ["22101", "22100", "22010-1210"].each ue zipvalidate.validate(zip).shouldBe tr } } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 119
  • Spock (1/3) • From the horse’s mouth: – « Spock is a testing and specification framework for Java and Groovy applications. What makes it stand out from the crowd is its beautiful and highly expressive specification language. » cification { cl ass HelloSpock extends spock.lang.Spe () {     def "can you figure out what I'm up to?"         expect:         name.size() == size         where: y"]         name << ["Kirk", "Spock", "Scott         size << [4, 5, 6]     } } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 120
  • Spock (2/3) • Extensible (but transparent) use of AST transformations to «pervert» the Groovy language – reuse of labels for the BDD actions • Spock brought Groovy 1.7’s enhanced asserts Condition not satisfied: max(a, b) == c |   |  |  |  | 3   1  3  |  2           false Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 121
  • Spock (3/3) • Another example of the expressive language once"() {     def "subscribe rs receive published events at least       when: publisher.send(event) vent)       then: (1.._) * subscriber.receive(e "]       where: ev ent << ["started", "paused", "stopped     } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 122
  • GMock (1/3) • GMock is a mocking framework for Groovy path/file.txt")) File mo ckFile = mock(File, constructor("/a/ ") mockFile.getName().returns("file.txt play { ")   def file = new File("/a/path/file.txt ()   assertEquals "file.txt", file.getName } • Mocking capabilities – method calls – constructor calls – property access – time matching – static calls – order matching – partial mocks – regex method matching Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 123
  • GMock (2/3) • Mocking method calls def loader = mock() loader.put("fruit").returns("apple") play { fruit")   assertEquals "apple", loader.put(" } • Mock static calls def mockMath = mock(Math) ) mockMath.static.random().returns(0.5 play {    assertEquals 0.5, Math.random() } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 124
  • GMock (3/3) • Expecting exceptions ception, "an exception") loader.put ("throw exception").raises(RuntimeEx • Time matching – never, once, atLeastOnce, atMostOnce, stub, times, atLeast, atMost ) mockLo ader.load(2).returns(3).atLeastOnce( play { 2)     assertEquals 3, mockLoader.load( 2)     assertEquals 3, mockLoader.load( } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 125
  • Gant • Gant is a tool for scripting Ant tasks using Groovy instead of XML to specify the logic includeTargets << gant.targets.Clean ] cleanPattern << ['**/*~', '**/*.bak' cleanDirectory << 'build' uff.') { target(stuff: 'A target to do some st println 'Stuff' depends clean Ant.' echo message: 'A default message from otherStuff() } her stuff') { target (otherStuff: 'A target to do some ot println 'OtherStuff' Ant.' echo message: 'Another message from clean() } setDefaultTarget stuff Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 126
  • Gradle (1/2) • From the website: « Gradle is an enterprise-grade build system providing: – A very flexible general purpose build tool like Ant – Switchable, build-by-convention frameworks à la Maven, for Java, Groovy and Scala projects –Groovy build scripts – Powerful support for multi-project builds – Dependency management based on Ivy – Full support for existing Maven or Ivy repository infra – Support for transitive dependency management – Ant tasks and builds as first class citizens. » Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 127
  • Gradle (2/2) • For example, for a classical Java project usePlugin ‘java’ repositories { mavenCentral() } dependencies { compile group: ‘commons-collection’, n: ‘3.2’ module: ‘commons-collection’, versio testCompile group: ‘junit’, module: ‘junit’, version: ‘4.+’ } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 128
  • Other build and quality tools • You can use Ant, Gant, Maven (GMaven plugin) or Gradle to build your projects – fits nicely in an existing build and continuous integration infrastructure • A few Groovy-friendly tools provide handy metrics – CodeNarc: provides various rules for static analysis of your Groovy codebase (style, size, braces, naming...) – Simian: detects duplication in your Groovy code base – Cobertura, Clover: gives code coverage metrics Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 129
  • HTTPBuilder (1/3) • HTTPBuilder provides a convenient builder API for complex HTTP requests ) def http = new HTTP Builder( 'http://ajax.googleapis.com' http.request(GET, JSON) { ' uri.path = '/ajax/services/search/web Hobbes'] ur i.query = [v: '1.0', q: 'Calvin and refox/3.0.4' headers.'User- Agent' = 'Mozilla/5.0 Ubuntu/8.10 Fi response.success = { resp, json -> println resp.statusLine json.responseData.results.each { Url}" println " ${ it.titleNoFormatting} : ${it.visible } } } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 130
  • HTTPBuilder (2/3) • Posting to a URL import groovyx.net.http.HTTPBuilder LENC import static groovyx.net.http.ContentType.UR   tuses/' ) def htt p = new HTTPBuilder( 'http://twitter.com/sta tpbuilder'] def postBody = [status: 'update!', source: 'ht http.post( path: 'update.xml', body: postBody, ->            requestContentType: URLENC ) { resp   usLine}"    println "Tweet response status: ${resp.stat    assert resp.statusLine.statusCode == 200 } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 131
  • HTTPBuilder (3/3) • Posting XML content to a URL http.request(POST, XML) {    body = {      auth {        user 'Bob'        password 'pass'      }    } } Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 132
  • GroovyWS (1/2) • Publishing and consuming WS-I compliant SOAP web services import groovyx.net.ws.WSClient def proxy = new WSClient( asmx?WSDL", "http://www.w3 schools.com/webservices/tempconvert. this.class.classLoader) proxy.initialize() t(0) def result = proxy.CelsiusToFahrenhei grees Farhenheit" println "You are probably freezing at ${result} de • Can also deal with complex objects Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 133
  • GroovyWS (2/2) • Publishing a service – considering a service class MathService { } double add(do uble arg0, double arg1) { arg0 + arg1 g0 } do uble square(double arg0) { arg0 * ar } – publishing the service import groovyx.net.ws.WSServer def server = new WSServer() /MathService") server.setNode(" MathService", "http://localhost:6980 server.start() Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 134
  • nd a Ag e • Summary •Q & A Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 135
  • Make your life easier
  • Great fit for Domain-Specific Languages
  • Rich and active ecosystem
  • Question & Answers Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 139
  • Picture credits • http://www.flickr.com/photos/featheredtar/2305070061/ • http://www.flickr.com/photos/joaomoura/2317171808/sizes/l/ • http://www.thedailygreen.com/cm/thedailygreen/images/WT/ • http://www.flickr.com/photos/wiccked/132687067/ christmas-tree-with-gifts-flipbook.jpg • http://www.flickr.com/photos/timsamoff/252370986/sizes/l/ • http://www.flickr.com/photos/chicoer2001/188468490/ • http://www.flickr.com/photos/29738009@N08/2975466425/sizes/l/ • http://www.flickr.com/photos/olibac/4054644737/ • http://www.flickr.com/photos/howie_berlin/180121635/sizes/o/ • http://www.flickr.com/photos/epsos/3384297473/ • http://www.flickr.com/photos/yogi/1281980605/sizes/l/ • http://www.flickr.com/photos/dorseygraphics/1336468896/sizes/l/ • http://media.techeblog.com/images/clapboard.jpg (clap) • http://www.flickr.com/photos/xcbiker/386876546/sizes/l/ • http://www.flickr.com/photos/diegocupolo/3614879332/ (flower power) • http://www.flickr.com/photos/pietel/152403711/sizes/o/ • http://www.flickr.com/photos/oskay/237442629/sizes/m/ (danger) • http://www.flickr.com/photos/forezt/192554677/sizes/o/ • http://www.partybox.co.uk/data/partyimages/ • http://keremkosaner.files.wordpress.com/2008/04/ softwaredevelopment.gif 250x250/6ftcutoutaustinpowers.jpg (austin powers) • http://www.jouy.inra.fr • http://www.flickr.com/photos/27663074@N07/3413698337/ (jeepers creepers) • http://www.flickr.com/photos/ejpphoto/408101818/sizes/o/ • http://www.flickr.com/photos/wheatfields/420088151/sizes/l/ • http://www.flickr.com/photos/solaro/2127576608/sizes/l/ • http://www.flickr.com/photos/therefromhere/518053737/sizes/l/ • http://www.flickr.com/photos/biggreymare/2846899405/sizes/l/ • http://www.flickr.com/photos/romainguy/230416692/sizes/l/ • http://www.flickr.com/photos/wwworks/2222523978/ (earth) • http://www.flickr.com/photos/addictive_picasso/2874279971/sizes/l/ • http://static-p3.fotolia.com/jpg/ 00/01/64/30/400_F_1643044_YrBQoPnt0SC5gHAueG0bhx20yCSL42.jpg • http://www.flickr.com/photos/huangjiahui/3127634297/sizes/l/ (trafic light) • http://www.flickr.com/photos/25831000@N08/3064515804/sizes/o/ • http://aldaria02.a.l.pic.centerblog.net/lz2levrz.jpg (griffon) • http://www.flickr.com/photos/lanier67/3147696168/sizes/l/ • http://www.flickr.com/photos/geishaboy500/104137788/ (soap) • http://www.flickr.com/photos/ktb/4916063/sizes/o/ • Matriochka http://lang.russe.free.fr/images/matriochka.jpg • http://www.flickr.com/photos/nathonline/918128338/sizes/l/ • • http://www.flickr.com/photos/kevinsteele/39300193/sizes/l/ • http://commons.wikimedia.org/wiki/File:Brueghel-tower-of-babel.jpg • http://commons.wikimedia.org/wiki/File:Platypus.jpg Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. 140