Part 1: Initializing the Project

Learn the basics of Gradle by creating a Java app using Gradle init.

In this section you will:

Initialize a new Gradle project
Build the project
Review Gradle’s project structure
Open the project in IntelliJ IDEA
Explore Gradle files and build scripts
Understand the Gradle wrapper

Step 0. Before you Begin

Make sure you have Gradle installed.
Install IntelliJ IDEA. The Community Edition is a free version of IntelliJ IDEA.

Step 1. Initializing the Project

To test the Gradle installation, run Gradle from the command-line:

$ gradle

Welcome to Gradle 8.6.

Directory '/' does not contain a Gradle build.

To create a new build in this directory, run gradle init

If Gradle is not installed, please refer to the installation section.

Create a new directory called tutorial and cd into it:

$ mkdir tutorial

$ cd tutorial

Run gradle init with the following parameters to generate a Java application:

$ gradle init --type java-application  --dsl kotlin

$ gradle init --type java-application  --dsl groovy

Select defaults for any additional prompts.

In this tutorial, all examples are macOS based.

When you are done, the directory should look as follows:

.
├── .gradle                 (1)
│   └── ⋮
├── gradle                  (2)
│   ├── libs.version.toml   (3)
│   └── wrapper
├── gradlew                 (4)
├── gradlew.bat             (5)
├── settings.gradle.kts     (6)
├── app                     (7)
│   ├── build.gradle.kts
│   └── src
└── ⋮                       (8)

1	Project-specific cache directory generated by Gradle.
2	Contains the JAR file and configuration of the Gradle Wrapper.
3	The version catalog which defines a set of versions for dependencies in a central location.
4	macOS and Linux script for executing builds using the Gradle Wrapper.
5	Windows script for executing builds using the Gradle Wrapper.
6	The project’s settings file where the list of subprojects is defined.
7	The source code and build configuration for the Java app.
8	Some additional Git files may be present such as `.gitignore`.

.
├── .gradle                 (1)
│   └── ⋮
├── gradle                  (2)
│   ├── libs.version.toml   (3)
│   └── wrapper
├── gradlew                 (4)
├── gradlew.bat             (5)
├── settings.gradle         (6)
├── app                     (7)
│   ├── build.gradle
│   └── src
└── ⋮                       (8)

1	Project-specific cache directory generated by Gradle.
2	Contains the JAR file and configuration of the Gradle Wrapper.
3	The version catalog which defines a set of versions for dependencies in a central location.
4	macOS and Linux script for executing builds using the Gradle Wrapper.
5	Windows script for executing builds using the Gradle Wrapper.
6	The project’s settings file where the list of subprojects is defined.
7	The source code and build configuration for the Java app.
8	Some additional Git files may be present such as `.gitignore`.

Step 2. Understanding the Gradle Wrapper

The Gradle Wrapper is the preferred way of starting a Gradle build. The Wrapper downloads (if needed) and then invokes a specific version of Gradle declared in the build.

In your newly created project, take a look at the files used by the Gradle Wrapper first. It consists of a shell script for macOS and Linux and a batch script for Windows .

These scripts allow you to run a Gradle build without requiring that Gradle be installed on your system. It also helps ensure that the same version of Gradle is used for builds by different developers and between local and CI machines.

From now on, you will never invoke Gradle directly; instead, you will use the Gradle wrapper.

Step 3. Invoking the Gradle Wrapper

Use the wrapper by entering the following command:

$ ./gradlew build

In Windows, the command is:

$ .\gradlew.bat build

The first time you run the wrapper, it downloads and caches the Gradle binaries if they are not already installed on your machine.

The Gradle Wrapper is designed to be committed to source control so that anyone can build the project without having to first install and configure a specific version of Gradle.

In this case, we invoked Gradle through the wrapper to build our project, so we can see that the app directory now includes a new build folder:

$ cd app

$ ls -al

drwxr-xr-x  10 gradle-user  staff  320 May 24 18:07 build
-rw-r--r--   1 gradle-user  staff  862 May 24 17:45 build.gradle.kts
drwxr-xr-x   4 gradle-user  staff  128 May 24 17:45 src

drwxr-xr-x  10 gradle-user  staff  320 May 24 18:07 build
-rw-r--r--   1 gradle-user  staff  862 May 24 17:45 build.gradle
drwxr-xr-x   4 gradle-user  staff  128 May 24 17:45 src

All the files generated by the build process go into the build directory unless otherwise specified.

Step 4. Understanding Gradle’s Project Structure

Let’s take a look at a standard Gradle project structure and compare it to our tutorial project:

A build contains:

A top level settings.gradle(.kts) file.
A root project.
One or more subprojects, each with its own build.gradle(.kts) file.

Some builds may contain a build.gradle(.kts) file in the root project but this is NOT recommended.

The libs.version.toml file is a version catalog used for dependency management which you will learn about in a subsequent section of the tutorial.

In this tutorial:

The root project is called tutorial and is defined with rootProject.name = "tutorial" in the settings.gradle file.
The subproject is called app and is defined with include("app") in the settings.gradle file.

The root project can be in the top-level directory or have its own directory.

A build:

Represents a bundle of related software that you can build, test, and/or release together.
Can optionally include other builds (i.e. additional software such as libraries, plugins, build-time tools, etc).

A project:

Represents a single piece of your architecture - a library, an app, a Gradle plugin, etc.
Can optionally contain other projects.

Step 5. Viewing Gradle files in an IDE

Open the project in IntelliJ IDEA by double-clicking on the settings.gradle.kts file in the tutorial directory. For Groovy DSL users, you may need to select the IntelliJ IDEA app when you click on the settings.gradle file:

Open the settings.gradle(.kts) and build.gradle(.kts) files in the IDE:

Step 6. Understanding the Settings file

A project is composed of one or more subprojects (sometimes called modules).

Gradle reads the settings.gradle(.kts) file to figure out which subprojects comprise a project build.

Take a look at the file in your project:

settings.gradle.kts

plugins {
    // Apply the foojay-resolver plugin to allow automatic download of JDKs
    id("org.gradle.toolchains.foojay-resolver-convention") version "0.7.0"
}

rootProject.name = "tutorial"
include("app")

settings.gradle

plugins {
    // Apply the foojay-resolver plugin to allow automatic download of JDKs
    id 'org.gradle.toolchains.foojay-resolver-convention' version '0.7.0'
}

rootProject.name = 'tutorial'
include('app')

The tutorial root project includes the app subproject. The presence of the include call turns the app directory into a subproject.

Step 7. Understanding the Build script

Each subproject contains its own build.gradle(.kts) file.

The build.gradle(.kts) file is the core component of the build process and defines the tasks necessary to build the project.

The build.gradle(.kts) file is read and executed by Gradle.

Take a closer look at the build file in your app subproject (under the app directory):

build.gradle.kts

plugins {
    // Apply the application plugin to add support for building a CLI application in Java.
    application
}

repositories {
    // Use Maven Central for resolving dependencies.
    mavenCentral()
}

dependencies {
    // Use JUnit Jupiter for testing.
    testImplementation(libs.junit.jupiter)

    testRuntimeOnly("org.junit.platform:junit-platform-launcher")

    // This dependency is used by the application.
    implementation(libs.guava)
}

// Apply a specific Java toolchain to ease working on different environments.
java {
    toolchain {
        languageVersion.set(JavaLanguageVersion.of(11))
    }
}

application {
    // Define the main class for the application.
    mainClass.set("running.tutorial.kotlin.App")
}

tasks.named<Test>("test") {
    // Use JUnit Platform for unit tests.
    useJUnitPlatform()
}

build.gradle

plugins {
    // Apply the application plugin to add support for building a CLI application in Java.
    id 'application'
}

repositories {
    // Use Maven Central for resolving dependencies.
    mavenCentral()
}

dependencies {
    // Use JUnit Jupiter for testing.
    testImplementation libs.junit.jupiter

    testRuntimeOnly 'org.junit.platform:junit-platform-launcher'

    // This dependency is used by the application.
    implementation libs.guava
}

// Apply a specific Java toolchain to ease working on different environments.
java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(11)
    }
}

application {
    // Define the main class for the application.
    mainClass = 'running.tutorial.groovy.App'
}

tasks.named('test') {
    // Use JUnit Platform for unit tests.
    useJUnitPlatform()
}

This build script lets Gradle know which dependencies and plugins the app subproject is using and where to find them. We will look at this in more detail in the following sections.

Next Step: Running Tasks >>

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