Learn about the Gradle build lifecycle and what each phase represents.

In this section, you will:

  • Understand the Build Lifecycle

  • Register and configure two tasks

  • Run the task to view the phases in action

Step 0. Before you Begin

  1. You initialized your Java app in part 1.

Step 1. Understanding the Build Lifecycle

A Gradle build has three distinct phases:

Phase 1 - Initialization

During the initialization phase, Gradle determines which projects will take part in the build, and creates a Project instance for each project.

Phase 2 - Configuration

During the configuration phase, the Project objects are configured using the build scripts of all projects in the build. Gradle determines the set of tasks to be executed.

Phase 3 - Execution

During the execution phase, Gradle executes each of the selected tasks.

When Gradle is invoked to execute a task, the lifecycle begins. Let’s see it in action.

gradle build lifecycle

Step 2. Update the Settings File

Add the following line to the top of the Settings file:

settings.gradle.kts
println("SETTINGS FILE: This is executed during the initialization phase")

Step 3. Update the Build Script

Add the following lines to the bottom of the Build script:

app/build.gradle.kts
println("BUILD SCRIPT: This is executed during the configuration phase")

tasks.register("task1"){
    println("REGISTER TASK1: This is executed during the configuration phase")
}

tasks.register("task2"){
    println("REGISTER TASK2: This is executed during the configuration phase")
}

tasks.named("task1"){
    println("NAMED TASK1: This is executed during the configuration phase")
    doFirst {
        println("NAMED TASK1 - doFirst: This is executed during the execution phase")
    }
    doLast {
        println("NAMED TASK1 - doLast: This is executed during the execution phase")
    }
}

tasks.named("task2"){
    println("NAMED TASK2: This is executed during the configuration phase")
    doFirst {
        println("NAMED TASK2 - doFirst: This is executed during the execution phase")
    }
    doLast {
        println("NAMED TASK2 - doLast: This is executed during the execution phase")
    }
}

Step 4. Run a Gradle Task

Run the task1 task that you registered and configured in Step 3:

$ ./gradlew task1

SETTINGS FILE: This is executed during the initialization phase     (1)

> Configure project :app
BUILD SCRIPT: This is executed during the configuration phase       (2)
REGISTER TASK1: This is executed during the configuration phase     (2)
NAMED TASK1: This is executed during the configuration phase        (2)

> Task :app:task1
NAMED TASK1 - doFirst: This is executed during the execution phase  (3)
NAMED TASK1 - doLast: This is executed during the execution phase   (3)

BUILD SUCCESSFUL in 25s
5 actionable tasks: 3 executed, 2 up-to-date
1 Initialization: Gradle executes settings.gradle.kts to determine the projects to be built and creates a Project object for each one.
2 Configuration: Gradle configures each project by executing the build.gradle.kts files. It resolves dependencies and creates a dependency graph of all the available tasks.
3 Execution: Gradle executes the tasks passed on the command line and any prerequisite tasks.

It is important to note that while task1 was configured and executed, task2 was not. This is called task configuration avoidance and prevents unnecessary work.

Task configuration avoidance is when Gradle avoids configuring task2 when task1 was called and task1 does NOT depend. on task2.

Next Step: Multi-Project Builds >>