Introduction To Gradle John Engelman Object Partners Inc @johnrengelman github.com/johnrengelman

Topics 1. What is Gradle? 2. Getting Started With Gradle 3. Building JVM Projects

What is Gradle? 1. Expressive, declarative, & maintainable build language 2. Dependency Resolver & Manager 3. Build Task Scheduler & Executor 4. Build By Convention Gradle is an opinionated framework on top of an unopinionated toolkit - Szczepan Faber

What Gradle is NOT!

It is NOT Groovy Ant! (That tool exists -> ) GANT

Core Gradle Features 1. Build-By-Convention w/ Flexibility 2. Project & Build Groovy DSL 3. Support for Ivy & Maven Dependencies 4. Multi-Project Builds 5. Easy to add custom logic 6. 1st class integration w/ Ant builds 7. Extensive public API and plugin ecosystem 8. Task UP-TO-DATE checking

The Quick & Dirty

A Typical Maven Build 11.28s (m v n p a c k a g e ) 2.061s (r m - r t a r g e t & & m v n p a c k a g e ) ~35 lines < p r o j e c t x m l n s = " h t t p : / / m a v e n . a p a c h e . o r g / P O M / 4 . 0 . 0 " x m l n s : x s i = " h t t p : / / w w w . w 3 . o r g / 2 0 0 1 / X M L S x s i : s c h e m a L o c a t i o n = " h t t p : / / m a v e n . a p a c h e . o r g / P O M / 4 . 0 . 0 h t t p : / / m a v e n . a p a c h e . o r g / m a v e n - v 4 _ < m o d e l V e r s i o n > 4 . 0 . 0 < / m o d e l V e r s i o n > < g r o u p I d > d e . u u l m . v s < / g r o u p I d > < a r t i f a c t I d > n e t t y - e x a m p l e < / a r t i f a c t I d > < p a c k a g i n g > j a r < / p a c k a g i n g > < v e r s i o n > 1 . 0 - S N A P S H O T < / v e r s i o n > < n a m e > n e t t y - e x a m p l e < / n a m e > < u r l > h t t p : / / m a v e n . a p a c h e . o r g < / u r l > < d e p e n d e n c i e s > < d e p e n d e n c y > < g r o u p I d > j u n i t < / g r o u p I d > < a r t i f a c t I d > j u n i t < / a r t i f a c t I d > < v e r s i o n > 3 . 8 . 1 < / v e r s i o n > < s c o p e > t e s t < / s c o p e > < / d e p e n d e n c y > < d e p e n d e n c y > < g r o u p I d > o r g . j b o s s . n e t t y < / g r o u p I d > < a r t i f a c t I d > n e t t y < / a r t i f a c t I d > < v e r s i o n > 3 . 2 . 2 . F i n a l < / v e r s i o n > < / d e p e n d e n c y > < / d e p e n d e n c i e s > < b u i l d > < p l u g i n s >

The Same Build w/ Gradle 11.07s (g r a d l e b u i l d ) 2.161s (r m - r b u i l d / & & g r a d l e b u i l d ) ~13 lines a p p l y p l u g i n : ' j a v a ' a p p l y p l u g i n : ' m a v e n ' g r o u p = ' d e . u u l m . v s ' v e r s i o n = ' 1 . 0 - S N A P S H O T ' r e p o s i t o r i e s { j c e n t e r ( ) } d e p e n d e n c i e s { c o m p i l e ' o r g . j b o s s . n e t t y : n e t t y : 3 . 2 . 2 . F i n a l ' t e s t C o m p i l e ' j u n i t : j u n i t : 3 . 8 . 1 ' } t a r g e t C o m p a t i b i l i t y = ' 1 . 6 ' s o u r c e C o m p a t i b i l i t y = ' 1 . 6 '

Getting Started w/ Gradle

Installing Gradle 1. Install GVM - 2. g v m i n s t a l l g r a d l e 2 . 0 http://gvmtool.net/

Starting a project 1. m k d i r t o d o & & c d t o d o 2. Initialize project Create & edit b u i l d . g r a d l e g r a d l e i n i t - - t y p e g r o o v y - l i b r a r y Convert existing Maven pom.xml: g r a d l e i n i t

Command Line Gradle

List Available tasks $ g r a d l e t a s k s : t a s k s - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - A l l t a s k s r u n n a b l e f r o m r o o t p r o j e c t - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - B u i l d t a s k s - - - - - - - - - - - a s s e m b l e - A s s e m b l e s t h e o u t p u t s o f t h i s p r o j e c t . b u i l d - A s s e m b l e s a n d t e s t s t h i s p r o j e c t . b u i l d D e p e n d e n t s - A s s e m b l e s a n d t e s t s t h i s p r o j e c t a n d a l l p r o j e c t s t h a t d e p e n d o n i t . b u i l d N e e d e d - A s s e m b l e s a n d t e s t s t h i s p r o j e c t a n d a l l p r o j e c t s i t d e p e n d s o n . c l a s s e s - A s s e m b l e s c l a s s e s ' m a i n ' . c l e a n - D e l e t e s t h e b u i l d d i r e c t o r y . j a r - A s s e m b l e s a j a r a r c h i v e c o n t a i n i n g t h e m a i n c l a s s e s . t e s t C l a s s e s - A s s e m b l e s c l a s s e s ' t e s t ' . . . .

Using the Gradle wrapper $ . / g r a d l e w t a s k s

Passing Properties - D m y p r o p = m y v a l u e : JVM System Properties for Gradle JVM - P p r o j e c t p r o p = p r o j e c t v a l : Gradle Project properties Specify Build File (default: b u i l d . g r a d l e ) - b < p a t h t o b u i l d f i l e > Logging - i , - - i n f o : Log more Gradle information - d , - - d e b u g : Log more information than Info - s , - - s t a c k t r a c e : Log stacktrace on error - q , - - q u i e t : Log errors only (or printlns)

Gradle Tasks

Single, atomic piece of work Consists of a list of "actions" Each "action" is a o r g . g r a d l e . a p i . A c t i o n C l o s u r e is coerced into A c t i o n t a s k h e l l o W o r l d { / / d e f i n e s a n e w t a s k w i t h n a m e ' h e l l o W o r l d ' d o L a s t { / / a d d a c t i o n t o t h e e n d o f t h e a c t i o n l i s t p r i n t l n ' H e l l o W o r l d ! ' } }

Build script is backed by a Gradle P r o j e c t instance t a s k is method from Gradle DSL (o r g . g r a d l e . a p i . P r o j e c t . t a s k ( S t r i n g n a m e , C l o s u r e c o n f i g u r e ) ) < < { . . } is shorthand for d o L a s t { . . } t a s k h e l l o W o r l d < < { p r i n t l n ' H e l l o W o r l d ! ' }

Task Dependencies & Ordering d e p e n d s O n creates an execution dependency All execution dependencies of a task must also be executed and completed before the task t a s k a < < { p r i n t l n ' a ' } t a s k b ( d e p e n d s O n : a ) < < { p r i n t l n ' b ' } $ g r a d l e b : a a : b b

f i n a l i z e d B y creates a finalization dependency The finalizer task is added if the finalized task is present in the task graph finalizer will execute after the finalized even when finalized fails finalizer will not execute if finalized did no work or was UP- TO-DATE t a s k c l e a n u p < < { p r i n t l n ' c l e a n u p ' } t a s k r u n < < p r i n t l n ' r u n ' r u n . f i n a l i z e d B y c l e a n u p / / ' r u n ' i s t h e " f i n a l i z e d " t a s k , ' c l e a n u p ' i s t h e " f i n a l i z e r " $ g r a d l e r u n : r u n r u n : c l e a n u p c l e a n u p

Task ordering allows you to specify ordering w/ creating an execution dependency m u s t R u n A f t e r Task A runs after Task B only if both are in the task graph Always respected s h o u l d R u n A f t e r Same as m u s t R u n A f t e r but less strict Ignored if Creates an ordering cycle When executing in parallel and all other dependencies are completed except the s h o u l d R u n A f t e r

t a s k f i r s t < < { p r i n t l n ' f i r s t ' } t a s k s e c o n d < < { p r i n t l n ' s e c o n d ' } s e c o n d . m u s t R u n A f t e r f i r s t $ g r a d l e s e c o n d : s e c o n d s e c o n d $ g r a d l e f i r s t : f i r s t f i r s t $ g r a d l e s e c o n d f i r s t : f i r s t f i r s t : s e c o n d s e c o n d

Gradle is Groovy! t a s k r e a d y ( ) < < { p r i n t l n ' R e a d y ' } 3 . t i m e s { n u m - > t a s k " c o u n t $ { n u m + 1 } " < < { p r i n t l n n u m + 1 } } t a s k g o ( ) < < { p r i n t l n ' G o ! ' } c o u n t 3 . d e p e n d s O n r e a d y c o u n t 2 . d e p e n d s O n c o u n t 3 c o u n t 1 . d e p e n d s O n c o u n t 2 g o . d e p e n d s O n c o u n t 1 t a s k c o u n t d o w n ( d e p e n d s O n : g o )

$ g r a d l e c o u n t d o w n - q R e a d y 3 2 1 G o !

Task name shortening $ g r a d l e h W : h e l l o W o r l d H e l l o w W o r l d ! B U I L D S U C C E S S F U L T o t a l t i m e : 0 . 6 7 3 s e c s

Excluding Tasks $ g r a d l e c o u n t d o w n - q - x r e a d y 3 2 1 G o !

Task Rules Dynamically creates tasks based on the requested task name t a s k s . a d d R u l e ( ' P a t t e r n : c o u n t d o w n < F r o m > ' ) { S t r i n g t a s k N a m e - > i f ( t a s k N a m e . s t a r t s W i t h ( ' c o u n t d o w n ' ) ) { t a s k ( t a s k N a m e ) < < { ( ( t a s k N a m e - ' c o u n t d o w n ' ) . t o I n t e g e r ( ) . . 0 ) . e a c h { p r i n t l n i t } } } } $ g r a d l e c o u n t d o w n 5 : c o u n t d o w n 5 5 4 3 2 1 0 $ g r a d l e c o u n t d o w n 2 : c o u n t d o w n 2 2 1 0

Task Inputs & Outputs Gradle tracks the inputs & outputs of a task Compares current inputs & outputs against previous runs If the same, task is considered UP-TO-DATE and is skipped Inputs consist of files and map of properties (String: Object) Outputs consists of files Tasks with no outputs, are never considered UP-TO-DATE and always executed Tasks with outputs but no inputs is considered UP-TO-DATE if the output hasn't changed

Gradle Properties Gradle Properties are loaded by the project From g r a d l e . p r o p e r t i e s in the rootDir of the project From the command line w/ - P p r o p e r t y = v a l u e Gradle Properties are inherited by child project and merged with child's properties / / g r a d l e . p r o p e r t i e s c u r r e n t V e r s i o n = 1 . 0 / / b u i l d . g r a d l e a p p l y p l u g i n : ' j a v a ' v e r s i o n = c u r r e n t V e r s i o n

Extra Properties Every enhanced object in the Gradle Domain Model can be extends via Extra Properties Each object has a e x t property to access the space Initially define using e x t . < p r o p e r t y N a m e > , then treat like project property e x t . f o o = ' b a r ' t a s k e c h o F o o < < { p r i n t l n f o o } t a s k b a z { e x t . f o o = ' b a z ' d o L a s t { p r i n t l n f o o } } $ g r a d l e e c h o F o o e c h o F o o 2 : e c h o F o o b a r : e c h o F o o 2 b a z

Variables Build scripts are Groovy, so define variables normally d e f t a s k N a m e s = [ ' f o o ' , ' b a r ' , ' b a z ' ] t a s k N a m e s . e a c h { n a m e - > t a s k s . c r e a t e ( n a m e ) < < { p r i n t l n n a m e } }

Gradle Daemon Reduce startup hit by keeping a live JVM Expires after 3 hours g r a d l e - - d a e m o n e c h o " o r g . g r a d l e . d a e m o n = t r u e " > > ~ / . g r a d l e / g r a d l e . p r o p e r t i e s

Debugging Gradle builds $ g r a d l e b u i l d - D o r g . g r a d l e . d e b u g = t r u e Attach debugger to port 5005.

Basics of a JVM Project Build

Build a Java/Groovy project $ g r a d l e b u i l d : c o m p i l e J a v a U P - T O - D A T E : c o m p i l e G r o o v y : p r o c e s s R e s o u r c e s U P - T O - D A T E : c l a s s e s : j a r : a s s e m b l e : c o m p i l e T e s t J a v a U P - T O - D A T E : c o m p i l e T e s t G r o o v y : p r o c e s s T e s t R e s o u r c e s U P - T O - D A T E : t e s t C l a s s e s : t e s t : c h e c k : b u i l d B U I L D S U C C E S S F U L T o t a l t i m e : 6 . 2 1 3 s e c s

Adding Dependencies Dependencies are added to a C o n f i g u r a t i o n JVM projects have compile, runtime, testCompile, testRuntime Configurations can extend other repositories compile extends runtime d e p e n d e n c i e s { c o m p i l e ' o r g . c o d e h a u s . g r o o v y : g r o o v y - a l l : 2 . 3 . 3 ' r u n t i m e ' m y s q l : m y s q l - c o n n e c t o r - j a v a : 5 . 1 . 3 1 ' t e s t C o m p i l e ' o r g . s p o c k f r a m e w o r k : s p o c k - c o r e : 0 . 7 - g r o o v y - 2 . 0 ' t e s t R u n t i m e ' c o m . h 2 d a t a b a s e : h 2 : 1 . 4 . 1 8 0 ' }

Locating Dependencies Gradle supplies some default repositories to search: jcenter, mavenCentral, mavenLocal Can also look at custom maven, ivy, and file system paths r e p o s i t o r i e s { m a v e n L o c a l ( ) j c e n t e r ( ) m a v e n C e n t r a l ( ) m a v e n { u r l ' h t t p : / / m a v e n . m y h o s t . c o m / ' c r e d e n t i a l s { u s e r n a m e ' u s e r n a m e ' p a s s w o r d ' p a s s w o r d ' } } i v y { u r l ' h t t p : / / i v y . m y h o s t . c o m ' } f l a t D i r { d i r f i l e ( ' r e p o ' ) } }

Project structure Follows the Maven convention + < p r o j e c t D i r > / + - - s r c / + - - m a i n / | + - - j a v a / | + - - g r o o v y / | + - - r e s o u r c e s / + - - t e s t / + - - j a v a / + - - g r o o v y / + - - r e s o u r c e s / But can be configured s o u r c e S e t s . m a i n . j a v a . s r c D i r s = [ ' s r c ' ] s o u r c e S e t s . t e s t . j a v a . s r c D i r s = [ ' t e s t ' ]

Project structure is tied to S o u r c e S e t s JVM projects have 2 - m a i n & t e s t Each S o u r c e S e t starts w/ j a v a r e s o u r c e s a p p l y p l u g i n : ' j a v a ' s o u r c e S e t s { m a i n { j a v a { . . . } r e s o u r c e s { . . . } } t e s t { j a v a { . . . } r e s o u r c e s { . . . } } }

Plugins can extends the SourceSet Gradle plugin adds < s o u r c e S e t > / g r o o v y Scala adds < s o u r c e S e t > / s c a l a a p p l y p l u g i n : ' g r o o v y ' a p p l y p l u g i n : ' s c a l a ' s o u r c e S e t s { m a i n { g r o o v y { . . . } s c a l a { . . . } } t e s t { g r o o v y { . . . } s c a l a { . . . } } }

Can declare additional S o u r c e S e t s (i.e "intTest") s o u r c e S e t s { i n t T e s t } Gradle automatically creates compile/runtime configurations for source sets / / N o n e e d t o d e c l a r e t h i s c o n f i g u r a t i o n s { i n t T e s t C o m p i l e i n t T e s t R u n t i m e }

Scripting Builds Extend builds through plugins Plugins come in 3 flavors Core Plugins: shipped w/ Gradle Script Plugins 3rd Party Plugins: resolved from outside sources

Creating Script Plugins Configure project, create tasks and set up dependencies in a filed Apply the file to your project / / d o c s . g r a d l e t a s k j a v a d o c J a r ( t y p e : J a r , d e p e n d s O n : j a v a d o c ) { c l a s s i f i e r = ' j a v a d o c ' f r o m ' b u i l d / d o c s / j a v a d o c ' } t a s k s o u r c e s J a r ( t y p e : J a r ) { c l a s s i f i e r = ' s o u r c e s ' f r o m s o u r c e S e t s . m a i n . a l l S o u r c e } b u i l d . d e p e n d s O n j a v a d o c J a r , s o u r c e s J a r / / b u i l d . g r a d l e a p p l y p l u g i n : ' g r o o v y ' a p p l y f r o m : f i l e ( ' d o c s . g r a d l e ' )

Adding 3rd party plugins Plugins must be available to Gradle itself They are not project dependencies, need something else. Configure Gradle's executiong using b u i l d s c r i p t { } Similar to configure a normal project Find plugins at Gradle Plugin Portal - http://plugins.gradle.org b u i l d s c r i p t { r e p o s i t o r i e s { j c e n t e r ( ) } d e p e n d e n c i e s { c l a s s p a t h ' o r g . g i t h u b . j e n g e l m a n . g r a d l e . p l u g i n s : s h a d o w : 1 . 0 . 2 ' } } a p p l y p l u g i n : ' j a v a ' a p p l y p l u g i n : ' c o m . g i t h u b . j o h n r e n g e l m a n . s h a d o w '

Gradle 2.1 Plugins DSL New plugin resolution via Gradle Plugin Portal & Bintray p l u g i n s { i d ' c o m . g i t h u b . j o h n r e n g e l m a n . s h a d o w ' v e r s i o n ' 1 . 0 . 2 ' }

Classpath Isolation All plugins are evaluated & executed with an isolated classloader Each classloader inherits from its parent classloader Apply a plugin in build.gradle and all subsequent script plugins can use classes from it Apply a plugin in a script plugin, then those classes are isolated to that script

/ / s h a d o w . g r a d l e b u i l d s c r i p t { r e p o s i t o r i e s { j c e n t e r ( ) } d e p e n d e n c i e s { c l a s s p a t h ' c o m . g i t h u b . j e n g e l m a n . g r a d l e . p l u g i n s : s h a d o w : 1 . 0 . 2 ' } } i m p o r t c o m . g i t h u b . j e n g e l m a n . g r a d l e . p l u g i n s . s h a d o w . S h a d o w P l u g i n a p p l y p l u g i n : S h a d o w P l u g i n / / b u i l d . g r a d l e a p p l y p l u g i n : ' g r o o v y ' a p p l y f r o m : f i l e ( ' s h a d o w . g r a d l e ' ) i m p o r t c o m . g i t h u b . j e n g e l m a n . g r a d l e . p l u g i n s . s h a d o w . t a s k s . S h a d o w J a r t a s k c u s t o m S h a d o w ( t y p e : S h a d o w J a r ) / / N o C l a s s D e f F o u n d E x c e p t i o n o r M i s s i n g P r o p e r t y E x c e p t i o n

Multi-Project Builds

Define sub-projects in s e t t i n g s . g r a d l e + < p r o j e c t D i r > + - - a p i / | + - - b u i l d . g r a d l e + - - c l i e n t / | + - - b u i l d . g r a d l e + - - s e r v e r / + - - b u i l d . g r a d l e / / s e t t i n g s . g r a d l e i n c l u d e " a p i " , " c l i e n t " , " s e r v e r " $ g r a d l e p r o j e c t s - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - R o o t p r o j e c t - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - R o o t p r o j e c t ' t o d o ' + - - - P r o j e c t ' : a p i ' + - - - P r o j e c t ' : c l i e n t ' \ - - - P r o j e c t ' : s e r v e r '

Declaring dependencies on projects / / s e r v e r / b u i l d . g r a d l e d e p e n d e n c i e s { c o m p i l e p r o j e c t ( " : a p i " ) / / d e p e n d s o n a r t i f a c t s o f t h e ' d e f a u l t ' c o n f i g u r a t i o n }

Enabling Parallel Builds $ g r a d l e b u i l d - - p a r a l l e l OR / / g r a d l e . p r o p e r t i e s o r ~ / . g r a d l e / g r a d l e . p r o p e r t i e s o r g . g r a d l e . p a r a l l e l = t r u e

Gradle References Gradle User Guide: http://www.gradle.org/docs/current/userguide/userguide.html Gradle DSL Reference: http://www.gradle.org/docs/current/dsl/

Gradle In Action (Benjamin Muschko)

OPI Java, Groovy, Javascript, Mobile, Open Source ~ 100 Senior Consultants Minneapolis, MN & Omaha, NE Chicago, IL & Denver, CO Average tenure > 5 years Founded in 1996 objectpartners.com @objectpartners objectpartners.com/blog