An introduction to Gradle for JVM people. Describes the basics of Groovy & the Gradle DSL. Shows projects in various JVM languages.

1. GRADLE IN 45MIN
Schalk Cronjé

2. ABOUT ME
Email:
Twitter / Ello : @ysb33r
ysb33r@gmail.com
Gradle plugins authored/contributed to: VFS, Asciidoctor,
JRuby family (base, jar, war etc.), GnuMake, Doxygen

3. GET YOUR DAILY GRADLE DOSE
@DailyGradle
#gradleTip

4. GRADLE
A next generation build-and-deploy
pipeline tool

5. MOST TRIVIAL JAVA PROJECT
apply plugin: 'java'
Will look for sources under src/main/java

6. JAVA PROJECT
repositories {
jcenter()
}
apply plugin : 'java'
dependencies {
testCompile 'junit:junit:4.1'
}

7. GRADLE DEPENDENCY
MANAGEMENT
Easy to use
Flexible to configure for exceptions
Uses dependencies closure
First word on line is usually name of a configuration.
Configurations are usually supplied by plugins.
Dependencies are downloaded from repositories
Maven coordinates are used as format

8. GRADLE REPOSITORIES
Specified within a repositories closure
Processed in listed order to look for dependencies
jcenter() preferred open-source repo.
mavenLocal(), mavenCentral(), maven {}
Ivy repositories via ivy {}
Flat-directory repositories via flatDir

9. GRADLE REPOSITORIES
repositories {
jcenter()
mavenCentral()
maven { url "https://plugins.gradle.org/m2/" }
}
repositories {
ivy {
url 'file://path/to/repo'
layout 'pattern', {
artifact '[module]/[revision]/[artifact](.[ext])'
ivy '[module]/[revision]/ivy.xml'
}
}
}

10. GRADLE DSL
Underlying language is Groovy
You don’t need to be a Groovy expert to be a Gradle power
user
Groovy doesn’t need ; in most cases
Groovy does more with less punctuation, making it an
ideal choice for a DSL
In most cases lines that do not end on an operator is
considered a completed statement.

11. GROOVY VS JAVA
In Groovy:
All class members are public by default
No need to create getters/setters for public fields
Both static & dynamic typing supported
def means Object

12. CALLING METHODS
class Foo {
void bar( def a,def b ) {}
}
def foo = new Foo()
foo.bar( '123',456 )
foo.bar '123', 456
foo.with {
bar '123', 456
}

13. CALLING METHODS WITH CLOSURES
class Foo {
void bar( def a,Closure b ) {}
}
def foo = new Foo()
foo.bar( '123',{ println it } )
foo.bar ('123') {
println it
}
foo.bar '123', {
println it
}

14. MAPS IN GROOVY
Hashmaps in Groovy are simple to use
def myMap = [ plugin : 'java' ]
Maps are easy to pass inline to functions
project.apply( plugin : 'java' )
Which in Gradle can become
apply plugin : 'java'

15. LISTS IN GROOVY
Lists in Groovy are simple too
def myList = [ 'clone', ''http://github.com/ysb33r/GradleLectures' ]
This makes it possible for Gradle to do
args 'clone', 'http://github.com/ysb33r/GradleLectures'

16. CLOSURE DELEGATION IN GROOVY
When a symbol cannot be resolved within a closure,
Groovy will look elsewhere
In Groovy speak this is called a Delegate.
This can be programmatically controlled via the
Closure.delegate property.

17. CLOSURE DELEGATION IN GROOVY
class Foo {
def target
}
class Bar {
Foo foo = new Foo()
void doSomething( Closure c ) {
c.delegate = foo
c()
}
}
Bar bar = new Bar()
bar.doSomething {
target = 10
}

18. MORE CLOSURE MAGIC
If a Groovy class has a method 'call(Closure)`, the object can
be passed a closure directly.
class Foo {
def call( Closure c) { /* ... */ }
}
Foo foo = new Foo()
foo {
println 'Hello, world'
}
// This avoids ugly syntax
foo.call({ println 'Hello, world' })

19. CLOSURE DELEGATION IN GRADLE
In most cases the delegation will be entity the closure is
passed to.
Will also look at the Project and ext objects.
The Closure.delegate property allows plugin writers
ability to create beautiful DSLs
task runSomething(type : Exec ) { cmdline 'git' }
is roughly the equivalent of
ExecTask runSomething = new ExecTask()
runSomething.cmdline( 'git' )

20. GRADLE TASKS
Can be based upon a task type
task runSomething ( type : Exec ) {
command 'git'
args 'clone', 'https://bitbucket.com/ysb33r/GradleWorkshop'
}
Can be free-form
task hellowWorld << {
println 'Hello, world'
}

21. GRADLE TASKS : CONFIGURATION VS
ACTION
Use of << {} adds action to be executed
Tasks supplied by plugin will have default actions
Use of {} configures a task

22. BUILDSCRIPT
The buildscript closure is special
It tells Gradle what to load into the classpath before
evaluating the script itself.
It also tells it where to look for those dependencies.
Even though Gradle 2.1 has added a new way of adding
external plugins, buildscript are much more flexible.

23. EXTENSIONS
Extensions are global configuration blocks added by
plugins.
Example: The jruby-gradle-base plugin will add a
jruby block.
apply plugin: 'com.github.jruby-gradle.base'
jruby {
defaultVersion = '1.7.11'
}

24. GRADLE COMMAND-LINE
gradle -v
gradle -h
gradle tasks
gradle tasks --info

25. GRADLE WRAPPER
Use wrapper where possible:
Eliminates need to install Gradle in order to build project
Leads to more reproducible builds
gradle wrapper --wrapper-version 2.12
./gradlew tasks

26. EXECUTING TASKS
./gradlew <taskName1> <taskName2> ...
./gradlew build

27. DEPENDENCIES
Examine dependencies involved with various configurations
./gradlew dependencies

28. SUPPORT FOR OTHER JVM
LANGUAGES

29. GROOVY PROJECT
repositories {
jcenter()
}
apply plugin : 'groovy'
dependencies {
compile 'org.codehaus.groovy:groovy-all:2.4.3'
testCompile ('org.spockframework:spock-core:1.0-groovy-2.4') {
exclude module : 'groovy-all'
}
}

30. SCALA PROJECT
repositories {
jcenter()
}
apply plugin : 'scala'
dependencies {
compile 'org.scala-lang:scala-library:2.11.8'
}

31. BUILDING KOTLIN
plugins {
id "com.zoltu.kotlin" version "1.0.1"
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib:1.0.1-1"
}

32. RUNNING JRUBY
plugins {
id 'com.github.jruby-gradle.base' version '1.2.1'
}
import com.github.jrubygradle.JRubyExec
dependencies {
jrubyExec "rubygems:colorize:0.7.7"
}
task printSomePrettyOutputPlease(type: JRubyExec) {
description "Execute our nice local print-script.rb"
script "${projectDir}/print-script.rb"
}
(Example from JRuby-Gradle project)

33. OTHER LANGUAGES
C++ / C / ASM / Resources (built-in)
Clojure (plugin)
Frege (plugin)
Golang (plugin)
Gosu (plugin)
Mirah (plugin in progress)

34. SUPPORT FOR OTHER
BUILDSYSTEMS
ANT (built-in)
GNU Make
MSBuild / xBuild
Grunt, Gulp
Anything else cra able via Exec or JavaExec task

35. BUILDING DOCUMENTATION
Javadoc, Groovydoc, Scaladoc (built-in)
Doxygen (C, C++) (plugin)
Markdown (plugin)
Asciidoctor (plugin)

36. BUILDING WITH ASCIIDOCTOR
plugins {
id 'org.asciidoctor.convert' version '1.5.2'
}

37. BUILDING WITH ASCIIDOCTOR
repositories {
jcenter()
}
asciidoctor {
sources {
include 'example.adoc'
}
backends 'html5'
}

38. PUBLISHING
Built-in to Maven, Ivy
Metadata publishing for native projects still lacking
Various plugins for AWS and other cloud storage
Plain old copies to FTP, SFTP etc.

39. MORE SUPPORT…
Official buildsystem for Android
Docker
Hadoop

40. TOUR DE FORCE
Build a distributable application packaged as as ZIP
Runnable via shell script or batch file
Contains classes written Java, Groovy & Kotlin source
Test source code with Spock Framework

41. TOUR DE FORCE
plugins {
id 'java'
id 'groovy'
id 'com.zoltu.kotlin' version '1.0.1'
id 'application'
}
repositories {
jcenter()
}
dependencies {
compile 'org.codehaus.groovy:groovy-all:2.4.3'
compile 'org.jetbrains.kotlin:kotlin-stdlib:1.0.1-1'
testCompile 'org.spockframework:spock-core:1.0-groovy-2.4'
}
version = '1.0'
mainClassName = "gradle.workshop.HelloJava"
compileGroovy.dependsOn compileKotlin

42. ENDGAME
Gradle is breaking new ground
Ever improving native support
Continuous performance improvements
Go find some more plugins at https://plugins.gradle.org

43. ABOUT THIS PRESENTATION
Written in Asciidoctor
Styled by asciidoctor-revealjs extension
Built using:
Gradle
gradle-asciidoctor-plugin
gradle-vfs-plugin
Code snippets tested as part of build
Source code:
https://github.com/ysb33r/GradleLectures/tree/MkJugMar201

44. THANK YOU
Email:
Twitter / Ello : @ysb33r
#idiomaticgradle
ysb33r@gmail.com
https://leanpub.com/idiomaticgradle

45. MIGRATIONS

46. ANT TO GRADLE
Reflect Ant Build into Gradle
ant.importBuild('build.xml')

47. MAVEN TO GRADLE
Go to directory where pom.xml is and type
gradle init --type pom

48. USEFUL STUFF

49. PUBLISHING VIA VFS
plugins {
id "org.ysb33r.vfs" version "1.0-beta3"
}
task publishToWebserver << {
vfs {
cp "${buildDir}/website",
"ftp://${username}:${password}@int.someserver.com/var/www",
recursive : true, overwrite : true
}
}