Gradle - Task

A build process execute a graph of tasks.

Task may just be:

• container (lifecycle task)
• or provided by plugin

• In Gradle - Kotlin DSL

tasks.register("Hello") {
  println("Hello")
}

• execution with the wrapper of the project

gradlew Hello

Hello

Tasks themselves consist of:

• Actions — pieces of work that do something, like copy files or compile source
• Inputs — values, files and directories that the actions use or operate on
• Outputs — files and directories that the actions modify or generate

A task should never call another task.

Tasks should define inputs and outputs to get the performance benefits of incremental build functionality.

When declaring the outputs of a task, make sure that the directory for writing outputs is unique among all the tasks in your project.

Intermingling or overwriting output files produced by different tasks compromises up-to-date checking causing slower builds. In turn, these filesystem changes may prevent Gradle’s build cache from properly identifying and caching what would otherwise be cacheable tasks.

Task are provided by:

• the core api.
• or plugin

Example for copy

task copy(type: Copy, group: "Custom", description: "Copies sources to the dest directory") {
    from "src"
    into "dest"
}

Kotlin

tasks.register("logInfo") {
  logging.captureStandardOutput(LogLevel.INFO)
  doFirst {
    println("A task message which is logged at INFO level")
  }
}

task echo(description: 'Default task') << {
    println 'Hello'
}
defaultTasks 'echo'

• In one project directory

gradlew tasks 
# or
gradlew tasks --all

• multi-project call from the root

gradle :services:webservice:tasks

tasks.withType(JavaCompile) {
        options.encoding = 'UTF-8'
}

• Lookup

val testTask =  tasks.getByName<Test>("test");
testTask.failFast = true;

• Or declarative

tasks.test {
   failFast = true;
}

gradle -q taskName

where:

• -q stands for quiet

• Specify a task to be excluded from execution.

gradle [-x|--exclude-task]

Ignore previously cached task results.

gradle --rerun-tasks

gradlew help --task <task>

Run the builds with all task actions disabled.

gradle [-m|--dry-run]

https://docs.gradle.org/current/userguide/tutorial_using_tasks.html#sec:task_dependencies

tasks.register("hello") {
    doLast {
        println("Hello world!")
    }
}
tasks.register("intro") {
    dependsOn("hello")
    doLast {
        println("I'm Gradle")
    }
}

See Gradle - Cache (.gradle)