Apache Groovy:the language and its ecosystem

Kostas Saidis, Agapios Avramidis

www.niovity.com

9th FOSSCOMMFree and Open Source Software Communities Meeting

April 16, 2016

Outline

Apache GroovyTop 10reasonsto use it

TheEcosystem

Niovity

We are a software companyusing a Java/Groovy/Javascript stack

Niovity Butterfly

We offer a web-based repository platformfor end-to-end data management

Our clients include Academic Libraries, Public Benefit Foundations, Research Institutes and Private Companies

www.OpenDataCloud.gr

2nd PrizePublic Open Data Hackathon 2014

Target audience

FOSS hackersthat the Java Platformand have a little experience withdynamic languages*

* like Javascript, Ruby, Python or Perl

Target audience

FOSS hackersthat dynamic languagesand have a little experience with theJava Platform

The Java what?

The Java Platform

1. The Java language2. The Java development kit (JDK)3. The Java virtual machine (JVM)

The JVM is the key component!

The JVM goes Polyglot

The Java Virtual MachineI A rock-solid, enterprise-grade runtime environment that can

execute multiple languages (not only Java).I Groovy, Javascript, Ruby, Python, Scala, Clojure, Kotlin, Fantom

and many others...

Most of the additional JVM languages are dynamic ones!

Dynamic LanguagesI Execute many common programming behaviors at runtime –in

contrast to static languages that perform them duringcompilation.

I Dynamic type checking.I Dynamic method dispatch†.I Support meta-programming (compiled constructs can be

modified programmatically at runtime).

†made faster with the invokedynamic bytecode instruction introduced in Java 7.

Flame War

Static vs Dynamic

Groovy

The best of both worlds in the JVM

Part I

Meet Apache GroovyA feature-rich, Java-friendly, dynamic language for the Java Platform

Groovy Tools

groovy-lang.org

1. groovyc: Compliles groovy sources to JVM bytecode (class files).2. groovysh: Executes code interactively (REPL).3. groovyConsole: GUI app for interactive code execution.4. groovy: Executes groovy scripts (you can use it like bash, perl,

python, etc).5. groovydoc: Generates documentation (like javadoc).6. Grape: An embedded jar dependency manager.

@groovylang #groovylang

The best place to start

Start from the Groovy console (GUI app)

Or the Groovy Web Console

Why Groovy

Top 10 + 1 reasons to use Groovy

Why Groovy #1

Groovy feels like a superset of Java with a simpler syntax

I Designed as a companion language for Java: Groovy issyntactically aligned with Java.

I Augments Java with additional features.I Literals for lists, maps, ranges, regular expressions, string

interpolation with GStrings.I GDK libraries extend JDK libraries in so many helpful ways.I Supported by all major Java IDEs (Eclipse, IntelliJ, Netbeans).

Groovy is Java on Steroids!

Groovy powerful switch statement1 switch(val) {2 case ”String”: //a string3 break4 case 10..100: //a range5 break6 case Date: //a date instance7 break8 case ~/gw+/: //a reg−ex9 break

10 case [’A’, ’B’]: //a list11 break12 case { it instanceOf Number && it > Integer.MAX_VALUE }13 //a closure14 break15 default:16 //the default, treated as an ”else” in Groovy.17 }

New methods introduced in Java libraries

List files recursively

groovy −e ”new File(’.’).eachFileRecurse { println it }”

I The method eachFileRecurse has been added to thejava.io.File class.

I Also an example of executing code given directly as text. Alldynamic languages support this.

A better syntax for common things

Example1 //lists2 List<Integer> list = [1, 2, 3]3 assert list[0] == 14 //operator overloading5 list << 46 assert list.size() == 47 //maps8 Map<String, String> map = [’one’:’1’, ”two”: ”2”, three:’3’]9 assert list[1] == map[’two’] as Integer

10 map.one = ’none’11 //GStrings12 String s = ”string”13 println ”value of s = $s”14 //Java ordinary methods are here15 map.put(s, ’4’)16 //with optional parentheses17 map.put s, 4

Why Groovy #2

Groovy is Object-oriented

I Supports Java Interfaces, Classes and Enums.I With some additional conventions and facilities (e.g. Groovy

properties) that make our life easier.I Supports Traits: a controlled way to implement multiple

inheritance, avoiding the diamond issue.

POGOs: Fat-free POJOs

Employee.groovy1 class Person {2 String name3 String surname4 }5 Person p = new Person(name:”N”, surname:”S”)6 assert p.name == ”N”7 assert p.getName() == ”N”8 test.surname = ”F”9 test.setSurname(”F”)

Traits

Maximize reuse1 interface Greeter {2 String greet()3 }4 trait Someone implements Greeter {5 String name6 String greet() { ”Hello, I’m $name, a ${class.getName()}!” }7 }8 trait Robot implements Greeter {9 String id

10 String greet() { ”Hello, I’m $id, a ${class.getName()}!” }11 }12 class Person implements Someone {13 String surname14 }15 class Cyborg implements Someone, Robot {16 String greet() { System.currentTimeMillis() % 2 == 1 ?

Someone.super.greet() : Robot.super.greet() }17 }

Why Groovy #3

Groovy supports Closures smartly and elegantly

A closure is an anonymous function together with a referencingenvironment.

Think of closures as anonymous blocks of code that:I can accept parameters or return a value,I can be assigned to variables,I can be passed as arguments,I capture the variables of their surrounding lexical scope.

Example1 //a closure assigned to a variable2 def multiplier = { Number x, Number y −> x * y }3 //invocation of the closure4 assert multiplier(2, 3) == 65 //partial application6 def doubler = multiplier.curry(2)7 assert doubler(3) == 68 //another doubler9 def otherDoubler = { it * 2 } //it −> the first arg

10 otherDoubler(3) == doubler(3)11 //closure as the last argument pattern12 void method(X x, Y y, Closure c)13 def c = { println ’booh booh’ }14 //invoke the method15 method(x, y, c)16 //alternate, more readable syntax17 method(x, y) { println ’booh booh’ }

Collection Manipulation1 //a groovy list (ArrayList behind the scenes)2 def list = [12, 2, 34, 4, 15]3 //Collection.collect(Closure c) − extra method available in

Groovy JDK4 //So, given a closure5 def inc = { it + 1 }6 //we can invoke7 list.collect(inc) == [13, 3, 35, 5, 16]8 //or pass the closure code directly9 assert list.collect{ it + 1 } == [13, 3, 35, 5, 16]

10 //some more fun11 list.findAll{ it > 10 }.groupBy{ it % 2 == 0 ? ’even’ : ’odd’ }

== [even:[12, 34], odd:[15]]

Owner and delegate1 class Test {2 long x = 23 def xTimes = { l −> x * l }4 }5 Test test = new Test()6 assert test.xTimes.owner == test7 assert test.xTimes.delegate == test8 test.xTimes(3) == 69 test.x = 3

10 test.xTimes(3) == 911 def map = [x:4]12 assert test.xTimes.resolveStrategy == Closure.OWNER_FIRST13 test.xTimes.resolveStrategy = Closure.DELEGATE_FIRST14 test.xTimes.delegate = map15 assert test.xTimes(3) == 12

Why Groovy #4

Groovy supports meta-proramming

I Annotations and AST transformations: compile-timemeta-programming.

I Meta-object protocol: runtime metaprogramming.

Compile-time meta-programming

Annotations example1 @Canonical Person {2 String name3 String surname4 }5 //@Canonical = @EqualsAndHashCode, @ToString and

@TupleConstructor6 def p1 = new Person(name:”N”, surname:”S”)7 //but also8 def p2 = new Person(”N”, ”S”)9 //Groovy == is Java’s equals()

10 assert p1 == p2

Runtime meta-programming

Introduce a new method in Strings1 String.metaClass.isUpperCase = {2 delegate.toCharArray().every{ Character.isUpperCase(it) }3 }4 String.metaClass.isLowerCase = {5 !delegate.isUpperCase()6 }7 assert ”JAVA”.isUpperCase()8 assert ”groovy”.isLowerCase()

Why Groovy #5

Groovy offers seamless integration with Java

I Syntactically correct Java will work in Groovy (with somegotchas).

I You get all groovy magic by just adding a jar in the classpath.I Call Groovy from Java == call Java from Java.I Joint compilation: mix Java and Groovy.

Mix Java and Groovy

Fetcher.java1 public interface Fetcher<V> {2 V fetch();3 }

Person.groovy1 @Canonical class Person implements Fetcher<String>{2 String name3 String surname4 @Override5 String toString() { ”$surname, $name” }6 @Override7 String fetch() { toString() }8 }

Mix Java and Groovy

UsingPerson.java1 public class UsingPerson {2 public static void main(String[] args) {3 Person p = new Person(”Theodoros”, ”Kolokotronis”);4 System.out.println(p.fetch());5 }6 }

Joint compilation

> groovyc Fetcher.java Person.groovy UsingPerson.java −j

> java −cp groovy−all.jar:. UsingPerson

> Kolokotronis, Theodoros

Why Groovy #6

Groovy is a Java-powered scripting language

Echo.java1 public class Echo {2 public static void main(String[] args) {3 if (args != null && args.length > 0) {4 //for Java < 8 you need a third−party library5 System.out.println(String.join(” ”, args));6 }7 }8 }

Echo.groovy (no boilerplate)1 if (args) {2 println args.join(’ ’)3 }

Querying a MySQL database using JDBC

db.groovy1 @GrabConfig(systemClassLoader=true)2 @Grab(’mysql:mysql−connector−java:5.1.6’)3 import groovy.sql.Sql4 try {5 def sql = Sql.newInstance(args[0], args[1], args[2], ”com.mysql

.jdbc.Driver”)6 def query=”select count(*) as c, date(cDate) as d from table

group by d order by c”7 sql.eachRow(query) { row −> println ”${row.c}:${row.d}” }8 }9 catch(e) { e.printStackTrace() }

Exploit the full power of Java effectively

Isn’t this Groovy or what?

> groovy db jdbc:mysql://localhost:3306/test test test123

Output1 9427:2004−08−202 6615:2004−10−293 5498:2004−10−084 5103:2004−08−315 4864:2004−10−146 4675:2004−10−317 4583:2004−10−058 4570:2004−08−219 4339:2004−09−30

10 4235:2004−10−30

Why Groovy #7

Groovy is well-suited for implementing custom DSLsDomain-Specific Languages are tailored to expressing a particularproblem.

For ExampleI Regular expressions: a DSL for text pattern matching.I SQL: a DSL for querying and managing relational data.

Groovy-based DSLs: builders, template engines and more.

FOSSCOMM 2016 Programme

The data1 def presentations = [2 [3 date : ’2016−04−16’,4 start: ’10:30’,5 end : ’11:00’,6 title: ’Welcome’,7 who : [’Software Libre Society’]8 ],9 [

10 date : ’2016−04−16’,11 start: ’16:00’,12 end : ’17:00’,13 title: ’Apache Groovy: the language and the ecosystem’,14 who : [’Agapios Avramidis’, ’Kostas Saidis’]15 ]16 ]

FOSSCOMM 2016 Programme

Groovy MarkupTemplateEngine1 yieldUnescaped ’<!DOCTYPE html>’2 html(lang:’el’) {3 head {4 meta (’http−equiv’:’...’)5 title (’FOSSCOMM 2016’)6 }7 body {8 [’2016−04−16’, ’2016−04−17’].each { date −>9 h1 (date)

10 list.findAll{it.date == date}.sort{it.start}.each{ p−>11 div {12 span (”${p.start} − ${p.end} − ”)13 big (p.title)14 br()15 strong (p.who.join(’,’))16 }17 }18 }19 }20 }

FOSSCOMM 2016 Programme

The generated HTML1 <!DOCTYPE html><html lang=’el’>2 <head>3 <meta http−equiv=’...’/><title>FOSSCOMM 2016</title>4 </head><body>5 <h1>2016−04−16</h1><div>6 <span>10:30 − 11:00 − </span><big>Welcome</big><br

/><strong>Software Libre Society</strong>7 </div><div>8 <span>16:00 − 17:00 − </span><big>Apache Groovy: the

language and the ecosystem</big><br/><strong>Agapios Avramidis,Kostas Saidis</strong>

9 </div><h1>2016−04−17</h1>10 </body>11 </html>

Why Groovy #8

Groovy supports optional type checking and static compilation

I In Groovy, most of the type checking is performed at runtime.I Use @TypeChecked & @CompileStatic annotations to maximize

static checks during compilation.I @TypeChecked performs static type checking, yet it

dispatches methods through the MOP (permits runtimemeta-programming).

I @CompileStatic = @TypeChecked+ “static” method linking (noMOP); is the closest you can get to javac-generated bytecode(in both behavior & performance).

Default type checking behavior

Example1 class Test {2 def s13 Integer s2 = 20164 void test() {5 s1 = ”fosscomm”6 assert s1.class == String.class7 s1 = 20168 s1.class == Integer.class9 s2 = ”fosscomm” //fails at runtime

10 }11 }12 new Test().test()

Enable static type checking

Example1 import groovy.transform.TypeChecked2 @TypeChecked class Test {3 def s14 Integer s2 = 20165 void test() {6 s1 = ”fosscomm”7 assert s1.class == String.class8 s1 = 20169 s1.class == Integer.class

10 s2 = ”fosscomm” //fails at compile−time11 }12 }13 new Test().test()

Languages and Typing

A statically-typed language resolves the types of variables duringcompilation you cannot change the type of a variable. Java, opt.Groovy

A dynamically-typed language resolves the types of variables atruntime you can change the type of a variable. Ruby, opt. Groovy

A strongly-typed language guarantees type conformance youcan’t coerce a variable to a wrong type. Java, Ruby, Groovy

A weakly-typed language has type abstractions that leak you canscrew everything up in all possible ways. C

Why Groovy #9

Groovy runs on Android

I Java on Android is very verbose(i.e. anonymous inner classes)I Use groovy 2.4.+ (smaller core jar, grooid compiler)I Supported by Gradle (plugin groovyx.grood.groovy-android) and

Android StudioI Groovy dynamic features can be used but avoid generating

classes at runtimeI Use @CompileStatic and properly configure ProGuard to be safe

Java and groovy on Android

Java1 button.setOnClickListener(new View.OnClickListener() {2 @Override3 void onClick(View v) {4 startActivity(intent);5 }6 });

Groovy1 button.onClickListener = { startActivity(intent) }

Why Groovy #10

A mature open source technology that is here to stay!

I More than a decade long history‡.I Free and Open Source Software (Apache License v2).I Joined the ASF in 2015.

‡Groovy was the first “second language” proposed for the JVM (back in 2004).

Why Groovy #10 + 1

Groovy has a vibrant community and ecosystem

Everything that runs on the JVM is part of the Groovy ecosystem.

Including all Java tools, libraries and frameworks out there!

Thank you!

Just kidding!

Part II

The Groovy EcosystemAwesome tools, libraries and frameworks written in Groovy

or for Groovy§

§We are only including projects with commit activity in 2016. Apologies if we missed some!

All things groovy

SysAdmin & DevOps

Building & Testing

Web & Cloud

Desktop & Mobile

Documents & Pages

Concurrency

Other

All projects are licensed under the Apache Software Foundation License v2, expect noted otherwise.

SysAdmin & DevOps

sdkmanA tool for managing different versions of SDKs

At a glance

sdkmanI Install, switch, remote and listing candidate SDKsI Inspired by RVM and rbenvI Written in bash and requires curl and unzipI Easy to install ( curl -s http://get.sdkman.io | bash)I Command line client (CLI) and APIsI Website

Example

List Candidatessdk list

List all versions of Groovy

sdk list groovy

Install latest Groovy

sdk install groovy

CRaSHA Shell for the JVM

At a glance

ConceptsI Modes

I Standalone and Attach through attach API of Hotspot JVM)I Embedded (web apps)

I ConnectorsI JVM, SSH, Telnet, Web (requires WebSocket)

FeaturesI Connect to any JVM (ssh, telnet, web)I Completion, help, pipes.I Built-in commands (jmx, jdbc, thread, memory usage)I Extensible (create new commands in java or groovy)I Authentication (simple, Jaas, key-based)I Free and Open Source Software (LGPL v2.1)I Website

GroovyServReduces startup time of the JVM

At a glance

GroovyServI Quick startup of Groovy scripts (groovyClient)I Utilizes a JVM process running in background (server)I If a server is not running when a client is invoked, the client

runs a server in backgroundI Available in sdkmanI Website

sshoogrA DSL for working with remote SSH servers

Example1 import static com.aestasit.infrastructure.ssh.DefaultSsh.*2 remoteSession(’user:pass@host:port’) {3 exec ’ls −la’4 remoteFile(’/tmp/test.txt’).text = ’test’5 //uploading6 scp {7 from { localFile ”$buildDir/test.file” }8 into { remoteFile ’/tmp/test.file’ }9 }10 }

Groovy VFSA DSL that wraps the Apache Commons VFS

Example1 def vfs = new VFS()2 //simple copy3 vfs.cp ’ftp://foo.example/myfile’, ’sftp://bar.example/yourfile’4 vfs {5 // Lists all files on a remote site6 ls (’http://first.example’) { println it.name }7 // Streams the output8 cat (’http://first.example/myfile’) { strm−>9 println strm.text10 }11 // Create a new folder on a remote site12 mkdir ’sftp://second.example/my/new/folder’13 }

Building & Testing

GradleEmerge from build hell

At a glance

GradleI Combines the best of Ant, Ivy and Maven (files, dependencies,

conventions)I In a smart and extensible way (Deep API, Groovy DSL, Plugins)I Offering clean builds that are easy to read and maintainI Polyglot (not only Java)I Multi-project buildsI Incremental and parallel executionI Backed by Gradle IncI Website

Example build script

build.gradle1 apply plugin: ”java”2 //Introduces a set of Maven−style conventions3 //(tasks, source locations, dependency configurations, etc)4 group = ”org.foo.something”5 version = ”1.0−SNAPSHOT”6 repositories {7 //resolve all external dependencies via Maven central8 mavenCentral()9 }

10 dependencies {11 //each name (compile, testCompile, etc) refers to12 //a configuration introduced by the java plugin13 compile ”commons−io:commons−io:2.4”14 testCompile ”junit:junit:4.11”15 runtime files(”lib/foo.jar”, ”lib/bar.jar”)16 }

SpockThe enterprise-ready testing and specification framework

At a glance

SpockI Tool for performing unit/integration/functional tests for Java &

Groovy software.I Combines JUnit, Mockito and JBehave (units, mocks and BDD)

using a Groovy DSL.I Well-structured, given-then-when/setup-expect-where

specifications.I That read like plain English (and generate readable reports, too).I Clear insights of what went wrong.I Parameterized tests, data-driven specifications.I Website

Example spock spec

DataDrivenSpec1 class DataDrivenSpec extends Specification {2 def ”maximum of two numbers”() {3 expect:4 Math.max(a, b) == c5 where:6 a << [3, 5, 9]7 b << [7, 4, 9]8 c << [7, 5, 9]9 }

10 def ”minimum of #a and #b is #c”() {11 expect:12 Math.min(a, b) == c13 where:14 a | b || c15 3 | 7 || 316 5 | 4 || 417 9 | 9 || 918 }19 }

GebA browser automation tool

At a glance

GebI Tool for functional/web/acceptance testing (integration with

Spock, JUnit, TestNG).I Also, can be used for scripting, scraping and general browser

automation.I Build on top of WebDriver library (Selinium 2.0)I Provides a content definition DSL (jQuery-like)I Website

Geb from groovy1 import geb.Browser2 Browser.drive {3 go ”http://myapp.com/login”4 assert $(”h1”).text() == ”Please Login”5 $(”form.login”).with {6 username = ”admin”7 password = ”password”8 login().click()9 }

10 assert $(”h1”).text() == ”Admin Section”11 }

BetamaxTool for mocking external HTTP resources in tests

At a glance

BetamaxI Mock HTTP resources such as Web services or REST APIs.I Inspired by Ruby’s VCR.I Intercepts HTTP connections, stores their responses to “tapes”,

and replays previously recorded responses from the tape.I Tapes are stored to disk as YAML files. Different tests can have

different tapes.I Works well with Geb, JUnit and Spock. One liner to add it to

Gradle.I Website

Example

A Spock spec with Betamax1 class TwitterServiceSpec {2 @Rule Recorder recorder = new Recorder()3 def twitterService = new TwitterService()4 @Betamax(tape=”twitter”)5 def ”searches tweets ok”() {6 when:7 def tweets = twitterService.search(”#hashtag”)8 then:9 tweets.every{ it.text ~= /#hashtag/ }

10 }11 }

CodeNarcA static code analysis tool for groovy

At a glance

CodenarcI Analyzes and reports code for defects and inconsistenciesI Reporting (HTML, XML)I Contains a predefined set of rules (348)I Provides a framework for creating new rulesI Integration with other tools (Gradle, Maven, Grails, Sonar,

Jenkins, Grails, Griffon)I Website

Using Codenarc

build.gradle1 apply plugin: ’codenarc’2 codenarcMain {3 configFile file(’config/codenarc−rules.groovy’)4 }5 codenarcTest {6 configFile file(’config/codenarc−test−rules.groovy’)7 }

config/codenarc-rules.groovy1 ruleset {2 description ’Rules for my Groovy Gradle Project’3 ruleset(’rulesets/basic.xml’) { exclude ’ClassForName’ }4 LineLength { length = 150 }5 StatelessClass {6 name = ’StatelessDao’7 applyToClassNames = ’*Dao’8 }9 }

LazybonesProject creation tool that uses packaged templates

At a glance

LazybonesI Project creation tool that helps you bootstrap a project from a

template.I Lazybones templates are like Maven archetypes or Yeoman

generators.I Project templates can incorporate sub-templates.I Simple and effective.I Available in sdkman.I Website

Example

Install Lazybones

sdk install lazybones

Use Lazybones to create a project

lazybones create <template name> [template version] <target

directory> [options]

lazybones create java−app my−app −Ppackage=org.foo.bar −−with

−git

lazybones generate controller

Web & Cloud

Mainly Java Projects

Spring IOThe most widely used

Java server-sideframework.Backed by Pivotal.

Spring Boot supportsGroovy scripts.

Vert.xThe polyglot toolkit forreactive applications

on the JVM.Backed by the Eclipse

Foundation.

Full support for Groovy.

ElasticSearchThe Java distributedcluster for real-time

search.Backed by Elastic.

Supports Groovyserver-side scripts and a

Groovy client.

GrailsPowerful web application framework for the JVM

At a glance

GrailsI Convention over configuration, app profiles, reasonable

defaults, opinionated APIs, DSLs and more.I Inspired by Ruby on Rails.I Wraps Spring MVC and offers a GORM supporting Hibernate,

MongoDB, Neo4j, Cassandra & Redis.I Over a 100 plugins.I Available in sdkman.I Website

Example

Hello world Web app with Grails

grails create−app helloworld

cd helloworld

grails create−controller hello

1 package helloworld2 class HelloController {3 def index() {4 render ”Hello World!”5 }6 }

grails run−app

RatpackLean & powerful HTTP apps for the JVM

At a glance

RatpackI A set of libraries that facilitate fast, efficient, scalable and

evolvable HTTP apps.I Flexible and unopinionated.I Inspired by Sinatra, built on Netty networking engine.I Asynchronous, non-blocking, event-driven architecture (like

node.js).I Offers lazybones templates.I Website

Example

Hello world Web app with Ratpack1 @Grapes([2 @Grab(’io.ratpack:ratpack−groovy:1.2.0’),3 @Grab(’org.slf4j:slf4j−simple:1.7.12’)4 ])5 import static ratpack.groovy.Groovy.ratpack6 ratpack {7 handlers {8 get {9 render ”Hello World!”

10 }11 get(”:name”) {12 render ”Hello $pathTokens.name!”13 }14 }15 }

GlideA toolkit for Google App Engine

At a glance

GlideI Lets you develop and deploy applications to Google App Engine

JavaI Best suited for small-medium complexity appsI Provides a simple Webb App StructureI Has almost zero configurationI Supports hot reloadingI Uses GaelykI Available in sdkmanI Website

Desktop & Mobile

GriffonA framework for developing desktop apps

At a glance

GriffonI Inspired by GrailsI Convention over Configuration, Don’t Repeat Yourself (DRY), MVCI Testing supported out of the boxI Swing and JavaFX UI toolkitsI Extensible via pluginsI Website

griffon create−app my−app

GroovyFXGroovy bindings for JAVA FX 8

At a glance

GroovyFXI Aims to simplify the development of Java FX applicationsI Relies on groovy’s DSL features and AST transformations to

reduce boilerplate.I Provides a SceneGraphBuilder, which supports for all JavaFX

componentsI Each class in JavaFX has a corresponding GroovyFX node (i.e.

Scene class will be scene node)I Website

Example

Hello world GroovyFX1 import static groovyx.javafx.GroovyFX.start2 start {3 stage(title: ’GroovyFX Hello World’, visible: true) {4 scene(fill: BLACK, width: 500, height: 250) {5 hbox(padding: 60) {6 text(text: ’Groovy’, font: ’80pt sanserif’) {7 fill linearGradient(endX: 0, stops: [PALEGREEN,

SEAGREEN])8 }9 text(text: ’FX’, font: ’80pt sanserif’) {

10 fill linearGradient(endX: 0, stops: [CYAN, DODGERBLUE])

11 effect dropShadow(color: DODGERBLUE, radius: 25,spread: 0.25)

12 }13 }14 }15 }16 }

SwissKnifeAnnotation Library for Android

At a glance

SwissKnifeI Based on ButterKnife and AndroidAnnotationsI Relies on groovy AST transformationsI Inject resourcesI Inject views dynamicallyI Add callback methods to actionsI Execute in the UI thread or the backgroundI Website

Inject Resources1 @StringRes(R.string.msg)2 String msg3 @AnimationRes(R.anim.fade_in)4 Animation fadeInAnim

Inject views1 @InjectView(R.id.first_button)2 Button button13 @InjectView(R.id.list_view)4 ListView listView

Add callback method1 @OnClick(R.id.button)2 public void onButtonClicked(Button button) {3 Toast.makeText(this, ”Button clicked”, Toast.LENGTH_SHOT).

show()4 }

Documents & Pages

GrainStatic website generator

At a glance

GrainI Supports compression and minification for sourcesI Has built-in SASS/SCSS supportI Supports Markdown, reStructuredText and AsciiDoctorI Each static resource is represented as a Groovy map.I Resources can be processed with groovy code

(SiteConfig.groovy)I Website

Example

Resource mapper closure:Executed upon change1 resource_mapper = { resources −>2 resources.collect { Map resource −>3 if (resource.location =~/\/blog\/.*/) {4 // Select all the resources which5 // contain files placed under /blog dir6 // Rewrite url for blog posts7 def unParsedDate = resource.date8 def date = Date.parse(site.datetime_format, resource.date)9 .format(’yyyy/MM/dd/’)

10 def title = resource.title.toLowerCase()11 .replaceAll(”\\s+”,”−”)12 resource + [url: ”/blog/$date$title/”]13 } else {14 resource15 }16 }17 }

Groovy Document BuilderA DSL for creating Word & PDF documents

Example1 @Grab(’com.craigburke.document:pdf:0.4.14’)2 @Grab(’com.craigburke.document:word:0.4.14’)3 import com.craigburke.document.builder.PdfDocumentBuilder4 import com.craigburke.document.builder.WordDocumentBuilder5 def word = new WordDocumentBuilder(new File(’example.docx’))6 def pdf = new PdfDocumentBuilder(new File(’example.pdf’))7 word.create {8 document {9 paragraph ’Hello World (Word)’10 }11 }12 pdf.create {13 document {14 paragraph ’Hello World (PDF)’15 }16 }

Concurrency

RxGroovyGroovy Reactive Extensions for the JVM

At a glance

RxGroovyI ReactivX: APIs for asynchronous programming with observable

streams (aka ReactiveExtensions –Rx).I RxGroovy is the Groovy adapter of RxJava.I ReactiveX is a combination of the best ideas from the Observer

pattern, the Iterator pattern, and functional programming.I Website

Example

Fetch wikipedia articles asynchronously1 def fetchWikipediaArticle(String... articleNames) {2 return Observable.create { subscriber −>3 Thread.start {4 for (articleName in articleNames) {5 if (subscriber.unsubscribed) {6 return7 }8 subscriber.onNext(new URL(”http://en.wikipedia.org/wiki/

${articleName}”).text)9 }

10 if (!subscriber.unsubscribed) {11 subscriber.onCompleted()12 }13 }14 return subscriber15 }16 }17 fetchWikipediaArticle(”Tiger”, ”Elephant”)18 .subscribe { println it.substring(0, 100) }

GParsConcurrency and parallelism framework for the JVM

At a glance

GParsI Offers high-level concurrency and parallelism while leveraging

the multi-core hardware.I Map/ReduceI Fork/JoinI ActorsI DataflowI Software Transactional MemoryI And more..I Website

NextflowA DSL for data-driven computational pipelines

At a glance

NextflowI Polyglot dataflows on Linux.I Nextflow scripts are defined by composing many different

processes.I Each process can be written in any scripting language

supported by Linux.I Coordinate and synchronize the processes execution by simply

specifying their inputs and outputs.I Requires Java 7, easy to install (curl -fsSL get.nextflow.io |

bash).I Based on GPars.I Website

Example

helloworld.nf1 str = Channel.from(’hello’, ’hola’, ’bonjour’, ’ciao’)2 process printEnv {3 input:4 env HELLO from str5 ’’’6 echo $HELLO world!7 ’’’8 }

hello world!

ciao world!

bonjour world!

hola world!

Other

GrooscriptGroovy to Javascript transpiler

Example1 @Grab(’org.grooscript:grooscript:1.2.3’)2 import org.grooscript.GrooScript3 def groovy = ’’’4 def sayHello = { println ”Hello ${it}!” }5 sayHello(’Javascript’)6 ’’’7 println GrooScript.convert groovy8 //the JS9 var sayHello = function(it) {10 return gs.println(”Hello ” + (it) + ”!”);11 };12 gs.execCall(sayHello, this, [”Javascript”]);

Conclusion

A language that doesn’t affect the wayyou think about programming is not

worth knowing.

Alan Perlis (1922 - 1990)ACM Turing Award, 1966

Apache Groovy

The best language for diving into dynamic featuresfor Java hackers

The best language for diving into the Java platformfor Javascripters, Rubyists and Pythonistas¶

Perl hackers are diving into Perl 6, aren’t they?

¶after Rhino/Nashorn, JRuby and Jython respectively

Thank you

@niovity

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