Gradle

Projects

• build script (in root dir)  "build.gradle"

• Build (1) -> (n) Projects -> sub projects

• "ProjectDescriptor" is the representation

Tasks

• Gradle provided tasks: e.g. Java "Test"

• Plugins provide more tasks

• In configuration phase a task graph is created - Directed Acyclic Graph

Plugins

Phases

• Initialization (setting): read setting file, determine participants, create instances

• Configuration (build scripts): evaluate build scripts, build a task graph

• Execution

Builds

Gradle Wrapper

• if only need to run

• script to invoke / download on demand gradle

• "gradlew" / "gradlew.bat" at root

Gradle uses caching to build faster

If task input / output not changed, task will be skipped

So avoid overlapping / overwriting out files

Kotlin is the recommended language

Simply use ".gradle.kts" where ".gradle" for groovy

Settings - "settings.gradle" - always include one even empty

Build script - "build.gradle"

buildSrc - included build for complex logics e.g. custom task and plugin implementation not shared

gradle.properties - properties 

• alternatively properties in build script or command line parameters

• keep properties separate to build logics

Always include one (otherwise gradle traverses to the root)

See https://docs.gradle.org/current/javadoc/org/gradle/api/initialization/Settings.html

The "org.gradle.api.initialization.Settings" instance one-to-one correspondes to the file

Use for: 

• assemble multi-project build (include, includeFlat)

  • automatically create a root project

    • default name: directory

  • "includeFlat" include project parallel to root

See https://docs.gradle.org/current/userguide/java_plugin.html#sec:java_project_layout

Works with Maven repository

Scopes

implementation (use in most case)

• maven "compile"

• use in most case

• available to projects applies "Java Plugin"

api

• maven "compile"

• available to projects applies "Java Library Plugin"

compileOnly

• maven "provided"

runtimeOnly

• maven "runtime"

testImplementation

• for that required to compile tests

testRuntimeOnly

• for that required to run tests

providedCompile

• for WAR plugin

• like compileOnly and make sure aren't packaged in the WAR file

providedRuntime

• for WAR plugin

• like compileOnly and make sure aren't packaged in the WAR file

To get started to build a project:

• check if wrapper is there - use wrapper

• "gradle projects" - list projects

• "gradle tasks" - find out tasks

  • gradle help --task <taskname>

• gradle <taskname>