# Building Groovy Applications Sample

version 8.14

- Groovy DSL

- Kotlin DSL

| You can open this sample in an IDE that supports Gradle.

This guide demonstrates how to create a Groovy application with Gradle using `gradle init`. You can follow the guide step-by-step to create a new project from scratch or download the complete sample project using the links above.

## What you’ll build

You’ll generate a Groovy application that follows Gradle’s conventions.

## What you’ll need

- A text editor or IDE - for example IntelliJ IDEA

- A Java Development Kit (JDK), version 8 or higher - for example AdoptOpenJDK

- The latest Gradle distribution

## Create a project folder

Gradle comes with a built-in task, called `init`, that initializes a new Gradle project in an empty folder. The `init` task uses the (also built-in) `wrapper` task to create a Gradle wrapper script, `gradlew`.

The first step is to create a folder for the new project and change directory into it.

    $ mkdir demo
    $ cd demo

## Run the init task

From inside the new project directory, run the `init` task using the following command in a terminal: `gradle init`. When prompted, select the `1: application` project type and `3: Groovy` as the implementation language. Next you can choose the DSL for writing buildscripts - `1 : Kotlin` or `2: Groovy`. For the other questions, press enter to use the default values.

The output will look like this:

    $ gradle init

    Select type of build to generate:
      1: Application
      2: Library
      3: Gradle plugin
      4: Basic (build structure only)
    Enter selection (default: Application) [1..4] 1

    Select implementation language:
      1: Java
      2: Kotlin
      3: Groovy
      4: Scala
      5: C++
      6: Swift
    Enter selection (default: Java) [1..6] 3

    Enter target Java version (min: 7, default: 21):

    Project name (default: demo):

    Select application structure:
      1: Single application project
      2: Application and library project
    Enter selection (default: Single application project) [1..2] 1

    Select build script DSL:
      1: Kotlin
      2: Groovy
    Enter selection (default: Kotlin) [1..2]

    Generate build using new APIs and behavior (some features may change in the next minor release)? (default: no) [yes, no]

    BUILD SUCCESSFUL
    1 actionable task: 1 executed

The `init` task generates the new project with the following structure:

    ├── gradle (1)
    │   ├── libs.versions.toml (2)
    │   └── wrapper
    │       ├── gradle-wrapper.jar
    │       └── gradle-wrapper.properties
    ├── gradlew (3)
    ├── gradlew.bat (3)
    ├── settings.gradle.kts (4)
    └── app
        ├── build.gradle.kts (5)
        └── src
            ├── main
            │   └── groovy (6)
            │       └── demo
            │           └── App.groovy
            └── test
                └── groovy (7)
                    └── demo
                        └── AppTest.groovy

    ├── gradle (1)
    │   ├── libs.versions.toml (2)
    │   └── wrapper
    │       ├── gradle-wrapper.jar
    │       └── gradle-wrapper.properties
    ├── gradlew (3)
    ├── gradlew.bat (3)
    ├── settings.gradle (4)
    └── app
        ├── build.gradle (5)
        └── src
            ├── main
            │   └── groovy (6)
            │       └── demo
            │           └── App.groovy
            └── test
                └── groovy (7)
                    └── demo
                        └── AppTest.groovy

1 | Generated folder for wrapper files
2 | Generated version catalog
3 | Gradle wrapper start scripts
4 | Settings file to define build name and subprojects
5 | Build script of `app` project
6 | Default Groovy source folder
7 | Default Groovy test source folder

You now have the project setup to build a Groovy application.

## Review the project files

The `settings.gradle(.kts)` file has two interesting lines:

settings.gradle.kts

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

settings.gradle

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

- `rootProject.name` assigns a name to the build, which overrides the default behavior of naming the build after the directory it’s in. It’s recommended to set a fixed name as the folder might change if the project is shared - e.g. as root of a Git repository.

- `include("app")` defines that the build consists of one subproject called `app` that contains the actual code and build logic. More subprojects can be added by additional `include(…​)` statements.

Our build contains one subproject called `app` that represents the Groovy application we are building. It is configured in the `app/build.gradle(.kts)` file:

app/build.gradle.kts

    plugins {
        groovy (1)
        application (2)
    }

    repositories {
        mavenCentral() (3)
    }

    dependencies {
        implementation(libs.groovy.all) (4)

        implementation(libs.guava) (5)

        testImplementation(libs.spock.core) (6)
        testImplementation(libs.junit)

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

    application {
        mainClass = "demo.App" (7)
    }

    tasks.named<Test>("test") {
        useJUnitPlatform() (8)
    }

app/build.gradle

    plugins {
        id 'groovy' (1)
        id 'application' (2)
    }

    repositories {
        mavenCentral() (3)
    }

    dependencies {
        implementation libs.groovy.all (4)

        implementation libs.guava (5)

        testImplementation libs.spock.core (6)
        testImplementation libs.junit

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

    application {
        mainClass = 'demo.App' (7)
    }

    tasks.named('test') {
        useJUnitPlatform() (8)
    }

1 | Apply the groovy Plugin to add support for Groovy.
2 | Apply the application plugin to add support for building a CLI application in Java.
3 | Use Maven Central for resolving dependencies.
4 | Use the latest Groovy version for building this library
5 | This dependency is used by the application.
6 | Use the awesome Spock testing and specification framework even with Java
7 | Define the main class for the application.
8 | Use JUnit Platform for unit tests.

The file `src/main/groovy/demo/App.groovy` is shown here:

Generated src/main/groovy/demo/App.groovy

    /*
     * This source file was generated by the Gradle 'init' task
     */
    package demo

    class App {
        String getGreeting() {
            return 'Hello World!'
        }

        static void main(String[] args) {
            println new App().greeting
        }
    }

The generated test, `src/test/groovy/demo/App.groovy` is shown next:

Generated src/test/groovy/demo/AppTest.groovy

    /*
     * This source file was generated by the Gradle 'init' task
     */
    package demo

    import spock.lang.Specification

    class AppTest extends Specification {
        def "application has a greeting"() {
            setup:
            def app = new App()

            when:
            def result = app.greeting

            then:
            result != null
        }
    }

The generated test class has a single Spock test. The test instantiates the `App` class, invokes a method on it, and checks that it returns the expected value.

## Run the application

Thanks to the `application` plugin, you can run the application directly from the command line. The `run` task tells Gradle to execute the `main` method in the class assigned to the `mainClass` property.

    $ ./gradlew run

    > Task :app:run
    Hello world!

    BUILD SUCCESSFUL
    2 actionable tasks: 2 executed

| The first time you run the wrapper script, `gradlew`, there may be a delay while that version of `gradle` is downloaded and stored locally in your `~/.gradle/wrapper/dists` folder.

## Bundle the application

The `application` plugin also bundles the application, with all its dependencies, for you. The archive will also contain a script to start the application with a single command.

    $ ./gradlew build

    BUILD SUCCESSFUL in 0s
    7 actionable tasks: 7 executed

If you run a full build as shown above, Gradle will have produced the archive in two formats for you: `app/build/distributions/app.tar` and `app/build/distributions/app.zip`.

## Publish a Build Scan

The best way to learn more about what your build is doing behind the scenes, is to publish a build scan. To do so, just run Gradle with the `--scan` flag.

    $ ./gradlew build --scan

    BUILD SUCCESSFUL in 0s
    7 actionable tasks: 7 executed

    Publishing a build scan to scans.gradle.com requires accepting the Gradle Terms of Service defined at https://gradle.com/terms-of-service.
    Do you accept these terms? [yes, no] yes

    Gradle Terms of Service accepted.

    Publishing build scan...
    https://gradle.com/s/5u4w3gxeurtd2

Click the link and explore which tasks where executed, which dependencies where downloaded and many more details!

## Summary

That’s it! You’ve now successfully configured and built a Groovy application project with Gradle. You’ve learned how to:

- Initialize a project that produces a Groovy application

- Run the build and view the test report

- Execute a Groovy application using the `run` task from the `application` plugin

- Bundle the application in an archive

## Next steps

To learn more about how you can further customize Groovy application projects, check out the following user manual chapters:

- Building Java & JVM projects

- Java Application Plugin documentation