Hands on the Gradle

Introduction to the Gradle build system and the community driven Android plugin. For DroidCon Berlin 2011 barcamp.

1. S Hands on the Gradle Painless Android builds © 2011 Matthias Käppler Qype GmbH
2. What is Gradle? S  Gradle is a task based build system. From files and configuration it assembles build artifacts. S  Gradle is flexible. It is not bound to any specific process or technology. S  Gradle uses a Groovy based DSL to write configuration. This makes it easy to read and write Gradle scripts.
3. The Gradle manifesto S  „Build scripts are code.“ S  Don‘t expect, allow. S  Don‘t re-invent, re-use. S  Don‘t inherit, inject. S  Scale to the complexity of a problem. – „Make the impossible possible, the possible easy, and the easy elegant.“
4. Gradle vs. Maven <build>
 <plugins>
 <plugin>
 <artifactId>maven-antrun-plugin</artifactId>
 <executions>
 <execution>
 <phase>install</phase>
 <goals>
 <goal>run</goal>
 </goals>
 <configuration>
 <tasks>
 <echo message="what’s with the bloat?" />
 </tasks>
 </configuration>
 </execution>
 </executions>
 </plugin> 
 </plugins>
 </build>
5. Gradle vs. Maven (cont.) println "dunno, must be a Maven thing."
6. Gradle vs. Maven (cont.) S  Maven is declarative. Gradle is imperative. S  Maven is verbose. Gradle is concise. S  Maven assumes Maven. Gradle doesn‘t. S  Maven scales poorly to simple problems. Gradle scales with the complexity of a problem.
7. Gradle vs. Maven (cont.) S  Maven has a rich plug-in ecosystem. Gradle still needs to catch-up here. S  Maven has very good IDE support. Gradle has... IDE support. S  Maven has project archetypes. Gradle doesn‘t.
8. How is Gradle used? $ls
 build/ build.gradle ... ... $gradle tasks $gradle clean build $gradle androidInstall androidInstrument
9. build.gradle env = System.getenv() dependsOnChildren() apply from: ‘shared.gradle' allprojects {
 apply plugin: 'java'
 } task hello << {
 println ‘hello from Gradle‘
 }
10. Demo Move along, nothing to see here.
11. More about tasks S  There are different ways how tasks can be used or exposed in a build script: 1 – by writing them 2 – through project.ant 3 – by applying a plug-in
12. Writing tasks task hello << {
 4.times { println ‘hello from Gradle‘ }
 }
 
 hello.dependsOn initLang
 
 hello.someProperty = 1
13. Writing tasks (cont.) project.task(‘hello‘, dependsOn: ‘initLang‘)
 
 greeter = { println it }
 
 hello.doLast greeter.curry(‘hello from Gradle‘)
14. Ant tasks S  Ant tasks are first class citizens in Gradle. You access them through Groovy‘s AntBuilder DSL. 
 myProp = ant.properties["my.prop"]
 
 ant.copy {
 from zipTree("/path/to/lib.jar")
 into "$buildDir/extracted-classes"
 exclude "com.example/**"
 }
15. Plug-ins S  Most of Gradle‘s functionality comes from plug-ins. This helps in keeping the core Gradle APIs lean and clean. 
 apply plugin: 'java'
 apply plugin: 'maven'
 
 ...
 
 $gradle clean install
16. Plug-ins (cont.) S  Writing Gradle plug-ins is very simple. Check this out. 
 class MyPlugin implements Plugin<Project> {
 def apply(Project project) {
 project.task(‘hello‘) << {
 println ‘hello, people‘
 }
 }
 }
17. Dependencies S  Gradle doesn‘t define ist own dependency management system. Instead, it builds on Apache Ivy. 
 repositories {
 mavenCentral()
 mavenRepo urls: "http://my.repo.com"
 flatDir dirs: "libs"
 }
18. Dependencies (cont.) S  Dependencies are grouped into configurations. A configuration is simply a set of files bound to a name. 
 dependencies {
 compile "commons-lang:commons-lang:2.5"
 compile fileTree(dir: "libs", include: "*.jar")
 testCompile "junit:junit:4.8.2"
 }
19. Android S  There‘s a Gradle plug-in for Android. 
 https://github.com/jvoegele/gradle-android-plugin
20. Setting it up S  Now:
 
 buildscript {
 
 repositories {
 mavenRepo(urls: 'http://jvoegele.com/maven2/‘)
 }
 
 dependencies {
 classpath 'com.jvoegele.gradle.plugins:android-plugin:0.9.8‘
 }
 }
 
 apply plugin: com.jvoegele.gradle.plugins.android.AndroidPlugin S  Soon:
 
 apply plugin: 'android'
21. What‘s in store S  The plug-in adds the following tasks: S  :androidProcessResources S  :androidPackage S  :androidInstall S  :androidInstrument S  [:proguard] 
 
 $gradle clean andInstall :test-proj:andInstr
22. Instrumentation tests androidInstrument {
 
 runners {
 
 run testpackage: "unit", with: "com.my.UnitTestRunner", name: "instrumentation-unit-tests"
 
 run annotation: "android.test.suitebuilder.annotation.Smoke"
 
 run with: "com.my.OtherTestRunner”, options: "…”
 
 }
 
 }
23. Thanks Thanks for listening!
24. Android in Practice Charlie Collins, Michael Galpin, Matthias Käppler •  Real world practical recipes •  Focus on intermediate to professional developers •  Two chapters on testing and build automation Summer 2011 MEAP edition available http://manning.com/collins