Gradle in pratice (EN)
In this training, we will learn how Gradle works and how use it in our projects. It’s just a fast presentation of this tool and you will find more informations on official website https://docs.gradle.org/current/userguide/userguide.html
Gradle is an open source tool for automating the build of your Java, Kotlin, Android, Web projects… This tool is like Ant and Maven. Gradle has the Ant flexibility and apply many Maven conventions. Maven helps to build only one projetc. But Gradle was created to be more flexible, you can build several artifacts. That’s why the Android community has chosen this tool.
Introduction
Highly customizable
you have a convention but everything is customizable. You can write your scripts in Groovy (default) or in Kotlin (default in the future)
Fast
Incremental build : Gradle completes reuses outputs from previous executions, processing only inputs that changed, and executing tasks in parallel.
Powerful
Gradle build projects in several languages but its success is linked to Android developers.
Useful
Based on Ivy and supports Maven, it simplifies the project dependencies (libraries). You can use transitive dependencies
Why a build tool?
Write once, run everywhere
Build your project
To generate your delivery packages of your app (apk, jar, war…)
To run tests
To generate documentation and reports
To deploy your app
…
Usage
In command line in a terminal
In your IDE (development tools to write and execute code) NetBeans, Eclipse or IntelliJ (we will use IntelliJ)
Online documentation is very complete https://docs.gradle.org/current/userguide/userguide.html
Principle
Gradle was not the first build tool. In the past we used Ant and after Maven
Ant is very powerful, but the configuration is not readable and difficult to use on a project with a lot of people
Maven is
very verbose (you have to write a lot of XML)
not very flexible (governance and execution)
Note | For the governance Maven is managed by only one person, Jason Vanzyl and his society Sonatype. it’s difficult to contribute to this project For Gradle it’s totally different. You can open projects on Github and see all the contributors. Gradle is alive, Maven is dying |
Starting with Gradle
Open a terminal on your laptop or computer…
To create and initialize a new Gradle project
mkdir gradle-demo
gradle initIn the console you should have the following output
❯ gradle init Starting a Gradle Daemon (subsequent builds will be faster) BUILD SUCCESSFUL in 3s 2 actionable tasks: 2 executed
Gradle should have generated this tree
|-- build.gradle // <b class="conum">(1)</b> |-- gradle | | -- wrapper | | -- gradle-wrapper.jar // <b class="conum">(2)</b> | | -- gradle-wrapper.properties // <b class="conum">(3)</b> |-- gradlew // <b class="conum">(4)</b> |-- gradlew.bat // <b class="conum">(5)</b> |-- settings.gradle // <b class="conum">(6)</b>
1. Gradle configuration script for the project
2. This jar contains Gradle Wrapper classes and libraries
3. Wrapper configuration file
4. and 5. these script are used to launch Gradle via the wrapper (2 scripts, one for Unix one for Windows)
6. general configuration file (used to declare Gradle sub modules, and global variables)
Gradle wrapper
When you use a build tool, all team members must use the same version.
From one project to another, you can have different versions of the tool (it’s difficult to maintain on your computer).
Gradle wrapper resolves these problems
Fix the Gradle version used in your project
Provides utilities to download itself automatically, even if you don’t have Gradle locally
$ ./gradlew -v Downloading https://services.gradle.org/distributions/gradle-5.6.2-bin.z ip...................................................................... ........................................................................ ........................................................................ Unzipping /home/devmind/.gradle/wrapper/dists/gradle-5.6.2-bin/dajvke9o8 kmaxbu0kc5gcgeju/gradle-5.6.2-bin.zip to /home/devmind/.gradle/wrapper/d ists/gradle-5.6.2-bin/dajvke9o8kmaxbu0kc5gcgeju Set executable permissions for: /home/devmind/.gradle/wrapper/dists/grad le-5.6.2-bin/dajvke9o8kmaxbu0kc5gcgeju/gradle-5.6.2/bin/gradle ------------------------------------------------------------ Gradle 5.6.2 ------------------------------------------------------------ Build time: 2017-10-02 15:36:21 UTC Revision: a88ebd6be7840c2e59ae4782eb0f27fbe3405ddf Groovy: 2.4.12 Ant: Apache Ant(TM) version 1.9.6 compiled on June 29 2015 JVM: 1.8.0_181 (Oracle Corporation 25.181-b13) OS: Linux 4.15.0-34-generic amd64
An example
Clone the Github project https://github.com/Dev-Mind/gradle-demo.git
Go in IntelliJ in the menu File → New → Project From Existing Sources
|-- build.gradle |-- gradle | | -- wrapper | | -- gradle-wrapper.jar | | -- gradle-wrapper.properties |-- src | | -- main | | -- java | | -- resources | | -- test | | -- java | | -- resources |-- gradlew |-- gradlew.bat |-- settings.gradle
This is a Java project. So we use Java plugin provided by Gradle
// Apply the java plugin to add support for Java apply plugin: 'java' // In this section you declare where to find the dependencies of your // project repositories { // Use 'jcenter' for resolving your dependencies. // You can declare any Maven/Ivy/file repository here. jcenter() } dependencies { // Dependencies for production compile 'org.springframework:spring-context:5.0.7.RELEASE' // Dependencies for test testCompile 'junit:junit:4.12' }
You can now launch this command
$ ./gradlew build Starting a Gradle Daemon (subsequent builds will be faster) BUILD SUCCESSFUL in 4s 5 actionable tasks: 5 executed
Gradle execute tasks and in our case Java plugin has launched 5 tasks to build the projet
With IntelliJ, we have a synthetic view of dependencies and tasks
$ ./gradlew tasks --all ------------------------------------------------------------ All tasks runnable from root project ------------------------------------------------------------ Build tasks ----------- assemble - Assembles the outputs of this project. build - Assembles and tests this project. buildDependents - Assembles and tests this project and all projects that depend on it. buildNeeded - Assembles and tests this project and all projects it depends on. classes - Assembles main classes. clean - Deletes the build directory. jar - Assembles a jar archive containing the main classes. testClasses - Assembles test classes. Build Setup tasks ----------------- init - Initializes a new Gradle build. wrapper - Generates Gradle wrapper files. Documentation tasks ------------------- javadoc - Generates Javadoc API documentation for the main source code. Help tasks ---------- buildEnvironment - Displays all buildscript dependencies declared in root project 'gradle-demo'. components - Displays the components produced by root project 'gradle-demo'. [incubating] dependencies - Displays all dependencies declared in root project 'gradle-demo'. dependencyInsight - Displays the insight into a specific dependency in root project 'gradle-demo'. dependentComponents - Displays the dependent components of components in root project 'gradle-demo'. [incubating] help - Displays a help message. model - Displays the configuration model of root project 'gradle-demo'. [incubating] projects - Displays the sub-projects of root project 'gradle-demo'. properties - Displays the properties of root project 'gradle-demo'. tasks - Displays the tasks runnable from root project 'gradle-demo'. Verification tasks ------------------ check - Runs all checks. test - Runs the unit tests. Other tasks ----------- compileJava - Compiles main Java source. compileTestJava - Compiles test Java source. processResources - Processes main resources. processTestResources - Processes test resources. Rules ----- Pattern: clean<TaskName>: Cleans the output files of a task. Pattern: build<ConfigurationName>: Assembles the artifacts of a configuration. Pattern: upload<ConfigurationName>: Assembles and uploads the artifacts belonging to a configuration. BUILD SUCCESSFUL in 0s 1 actionable task: 1 executed
How Gradle works ?
1. Gradle connects to a remote plugin repository to load them. A plugin brings a task set
2. Gradle connects to a remote library repository and retrieves those declared for execution and testing
3. A task will act with our application
4. A task has a result (OK, KO, directory deletion, packaging jar …)
So, a project managed by Gradle is a configuration file that will indicate * how to download Gradle plugins (that provide a set of tasks)
* how to download dependencies of our project (Java libraries)
* tasks define a life cycle
* everything is configured via a DSL (Domain Specific Language) written in Groovy or Kotlin
Tasks
You have many predefined tasks (provided by plugins)
Defines what to do on a set of resources
A task may depend on one or more tasks.
Gradle creates a Directed Acyclic Graph (DAG) that defines a path to a task
Dependant task
Add these lines to your build.gradle file
task hello { doLast { println 'Hello' } } task world(dependsOn: hello) { doLast { println 'World' } }
Test by launching theses tasks
$ ./gradlew hello $ ./gradlew world
Life cycle
A Gradle build has 3 steps
Initialization
Gradle determines which projects are involved in the build. A project can have subprojects. All of them have a build.gradle.
Configuration
Gradle parses the build.gradle configuration file (or more if subprojects). After this step, Gradle has his task tree
Execution Gradle execute one or several tasks (arguments added to ./gradlew) according to this task graph. Gradle execute tasks one by one in the order defined in the graph.
Plugins
A plugin provide a task set and entry points to configure this plugin. For example
apply plugin : 'java'
Effect of this line :
Another example
In the next TP we will use Spring and Spring Boot. We will use Gradle to manage our projects
buildscript { repositories { repositories { // <b class="conum">(1)</b> mavenCentral() } dependencies { classpath("org.springframework.boot:spring-boot-gradle-plugin:2.0.4.RELEASE") // <b class="conum">(2)</b> } } repositories { mavenCentral() // <b class="conum">(1)</b> } apply plugin: 'org.springframework.boot' // <b class="conum">(3)</b> apply plugin: 'io.spring.dependency-management' // <b class="conum">(3)</b> dependencies { compile('org.springframework.boot:spring-boot-starter-web') testCompile('org.springframework.boot:spring-boot-starter-test') } bootRun{ // <b class="conum">(4)</b> sourceResources sourceSets.main } }
1. Remote repository for the plugins
2. We declare a dependancy to the Spring Boot Gradle plugin
3. We use this plugin
4. Personnalization of the plugin
Each plugin has a documentation https://docs.spring.io/spring-boot/docs/2.0.5.RELEASE/gradle-plugin/reference/html/
Customize tasks
Open your project gradle-demo in IntelliJ and add the following code
println 'This is executed during the configuration phase.' task configured { println 'This (configured) is also executed during the configuration phase.' } task testWrite { doLast { println 'This (testWrite) is executed during the execution phase.' } } task testWriteBoth { doFirst { println 'This (testWriteBoth) is executed first during the execution phase.' } doLast { println 'This (testWriteBoth) is executed last during the execution phase.' } println 'This (testWriteBoth) is executed during the configuration phase as well.' }
Launch
$ ./gradlew tasks
Then
$ ./gradlew testWrite
And
$ ./gradlew testWriteBoth
Try to understand what happens ?
$ ./gradlew tasks > Configure project : This is executed during the configuration phase. This (configured) is also executed during the configuration phase. This (testWriteBoth) is executed during the configuration phase as well. > Task :tasks ------------------------------------------------------------ All tasks runnable from root project ------------------------------------------------------------ Build tasks ----------- assemble - Assembles the outputs of this project. build - Assembles and tests this project. buildDependents - Assembles and tests this project and all projects that depend on it. buildNeeded - Assembles and tests this project and all projects it depends on. classes - Assembles main classes. clean - Deletes the build directory. jar - Assembles a jar archive containing the main classes. testClasses - Assembles test classes. Build Setup tasks ----------------- init - Initializes a new Gradle build. wrapper - Generates Gradle wrapper files. Documentation tasks ------------------- javadoc - Generates Javadoc API documentation for the main source code. Help tasks ---------- buildEnvironment - Displays all buildscript dependencies declared in root project 'gradle-demo'. components - Displays the components produced by root project 'gradle-demo'. [incubating] dependencies - Displays all dependencies declared in root project 'gradle-demo'. dependencyInsight - Displays the insight into a specific dependency in root project 'gradle-demo'. dependentComponents - Displays the dependent components of components in root project 'gradle-demo'. [incubating] help - Displays a help message. model - Displays the configuration model of root project 'gradle-demo'. [incubating] projects - Displays the sub-projects of root project 'gradle-demo'. properties - Displays the properties of root project 'gradle-demo'. tasks - Displays the tasks runnable from root project 'gradle-demo'. Verification tasks ------------------ check - Runs all checks. test - Runs the unit tests. Rules ----- Pattern: clean<TaskName>: Cleans the output files of a task. Pattern: build<ConfigurationName>: Assembles the artifacts of a configuration. Pattern: upload<ConfigurationName>: Assembles and uploads the artifacts belonging to a configuration. To see all tasks and more detail, run gradlew tasks --all To see more detail about a task, run gradlew help --task <task>
Dependencies
Several dependency types
Plugins
buildscript { repositories { dependencies { classpath("org.springframework.boot:spring-boot-gradle-plugin:2.0.4.RELEASE") // <b class="conum">(2)</b> } } }
Java libraries for code and test
dependencies { compile('org.springframework.boot:spring-boot-starter-web:2.0.4.RELEASE') testCompile('org.springframework.boot:spring-boot-starter-test:2.0.4.RELEASE') }
$ ./gradlew dependencies > Task :dependencies ------------------------------------------------------------ Root project ------------------------------------------------------------ apiElements - API elements for main. (n) No dependencies archives - Configuration for archive artifacts. No dependencies compile - Dependencies for source set 'main' (deprecated, use 'implementation ' instead). \--- org.springframework:spring-context:5.0.7.RELEASE +--- org.springframework:spring-aop:5.0.7.RELEASE | +--- org.springframework:spring-beans:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) +--- org.springframework:spring-beans:5.0.7.RELEASE (*) +--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- org.springframework:spring-expression:5.0.7.RELEASE \--- org.springframework:spring-core:5.0.7.RELEASE (*) compileClasspath - Compile classpath for source set 'main'. \--- org.springframework:spring-context:5.0.7.RELEASE +--- org.springframework:spring-aop:5.0.7.RELEASE | +--- org.springframework:spring-beans:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) +--- org.springframework:spring-beans:5.0.7.RELEASE (*) +--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- org.springframework:spring-expression:5.0.7.RELEASE \--- org.springframework:spring-core:5.0.7.RELEASE (*) compileOnly - Compile only dependencies for source set 'main'. No dependencies default - Configuration for default artifacts. \--- org.springframework:spring-context:5.0.7.RELEASE +--- org.springframework:spring-aop:5.0.7.RELEASE | +--- org.springframework:spring-beans:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) +--- org.springframework:spring-beans:5.0.7.RELEASE (*) +--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- org.springframework:spring-expression:5.0.7.RELEASE \--- org.springframework:spring-core:5.0.7.RELEASE (*) implementation - Implementation only dependencies for source set 'main'. (n) No dependencies runtime - Runtime dependencies for source set 'main' (deprecated, use 'runtimeOnly ' instead). \--- org.springframework:spring-context:5.0.7.RELEASE +--- org.springframework:spring-aop:5.0.7.RELEASE | +--- org.springframework:spring-beans:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) +--- org.springframework:spring-beans:5.0.7.RELEASE (*) +--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- org.springframework:spring-expression:5.0.7.RELEASE \--- org.springframework:spring-core:5.0.7.RELEASE (*) runtimeClasspath - Runtime classpath of source set 'main'. \--- org.springframework:spring-context:5.0.7.RELEASE +--- org.springframework:spring-aop:5.0.7.RELEASE | +--- org.springframework:spring-beans:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) +--- org.springframework:spring-beans:5.0.7.RELEASE (*) +--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- org.springframework:spring-expression:5.0.7.RELEASE \--- org.springframework:spring-core:5.0.7.RELEASE (*) runtimeElements - Elements of runtime for main. (n) No dependencies runtimeOnly - Runtime only dependencies for source set 'main'. (n) No dependencies testCompile - Dependencies for source set 'test' (deprecated, use 'testImplementation ' instead). +--- org.springframework:spring-context:5.0.7.RELEASE | +--- org.springframework:spring-aop:5.0.7.RELEASE | | +--- org.springframework:spring-beans:5.0.7.RELEASE | | | \--- org.springframework:spring-core:5.0.7.RELEASE | | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE (*) | +--- org.springframework:spring-beans:5.0.7.RELEASE (*) | +--- org.springframework:spring-core:5.0.7.RELEASE (*) | \--- org.springframework:spring-expression:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- junit:junit:4.12 \--- org.hamcrest:hamcrest-core:1.3 testCompileClasspath - Compile classpath for source set 'test'. +--- org.springframework:spring-context:5.0.7.RELEASE | +--- org.springframework:spring-aop:5.0.7.RELEASE | | +--- org.springframework:spring-beans:5.0.7.RELEASE | | | \--- org.springframework:spring-core:5.0.7.RELEASE | | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE (*) | +--- org.springframework:spring-beans:5.0.7.RELEASE (*) | +--- org.springframework:spring-core:5.0.7.RELEASE (*) | \--- org.springframework:spring-expression:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- junit:junit:4.12 \--- org.hamcrest:hamcrest-core:1.3 testCompileOnly - Compile only dependencies for source set 'test'. No dependencies testImplementation - Implementation only dependencies for source set 'test'. (n) No dependencies testRuntime - Runtime dependencies for source set 'test' (deprecated, use 'testRuntimeOnly ' instead). +--- org.springframework:spring-context:5.0.7.RELEASE | +--- org.springframework:spring-aop:5.0.7.RELEASE | | +--- org.springframework:spring-beans:5.0.7.RELEASE | | | \--- org.springframework:spring-core:5.0.7.RELEASE | | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE (*) | +--- org.springframework:spring-beans:5.0.7.RELEASE (*) | +--- org.springframework:spring-core:5.0.7.RELEASE (*) | \--- org.springframework:spring-expression:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- junit:junit:4.12 \--- org.hamcrest:hamcrest-core:1.3 testRuntimeClasspath - Runtime classpath of source set 'test'. +--- org.springframework:spring-context:5.0.7.RELEASE | +--- org.springframework:spring-aop:5.0.7.RELEASE | | +--- org.springframework:spring-beans:5.0.7.RELEASE | | | \--- org.springframework:spring-core:5.0.7.RELEASE | | | \--- org.springframework:spring-jcl:5.0.7.RELEASE | | \--- org.springframework:spring-core:5.0.7.RELEASE (*) | +--- org.springframework:spring-beans:5.0.7.RELEASE (*) | +--- org.springframework:spring-core:5.0.7.RELEASE (*) | \--- org.springframework:spring-expression:5.0.7.RELEASE | \--- org.springframework:spring-core:5.0.7.RELEASE (*) \--- junit:junit:4.12 \--- org.hamcrest:hamcrest-core:1.3 testRuntimeOnly - Runtime only dependencies for source set 'test'. (n) No dependencies (*) - dependencies omitted (listed previously) BUILD SUCCESSFUL in 0s 1 actionable task: 1 executed
1. Gradle looks in his cache if the dependency is present
2. It parses the given remote repository(ies), downloads the dependency and stores it in his cache
3. Dependency can be provided to project
4. If this dependency has another dependencies, Gradle loads them transitively
When an dependency needs to be loaded
The repositories are analyzed in the order of their definition.
Maven or Ivy repositories can be used
If the version number is dynamic like 1.+ Gradle will take the highest version (For example if you have versions 1.1, 1.2, 1.3, 1.+ is the 1.3 version) ⇒ bad practice
If the target is a Maven repository and the pom.xml has a parent, Gradle tries to load them
Build scan
Gradle provide a tool online to analyse your builds.
This tool is optimized for Gradle Entreprise, but some features are available on the free version
To use this tool, you have to update your build.gradle file and add
plugins { id 'com.gradle.build-scan' version '1.16' } buildScan { termsOfServiceUrl = 'https://gradle.com/terms-of-service'; termsOfServiceAgree = 'yes' }
You can now launch a scan
$ ./gradlew build --scan BUILD SUCCESSFUL in 0s 5 actionable tasks: 5 up-to-date Publishing build scan... https://gradle.com/s/cyyg2brvlolaa
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