# Part 2: The Build Lifecycle

version 8.12

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.

## 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")

settings.gradle

    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")
        }
    }

    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 >>