# Part 1: Initializing the Project

version 9.7.1

Learn the basics of developing Gradle plugins starting with `gradle init`.

In this section, you’ll:

- Initialize a Gradle plugin project with `gradle init`.

- Review the generated project structure and files.

- Understand the "Hello, World" plugin that was generated.

- Get a clear picture of the Slack Notification plugin we’re going to build.

- Set up the necessary Slack Client API credentials.

## Step 0: Before you Begin

Before we start, make sure you have everything you need:

1. Gradle Installed: Check that you have Gradle installed by running `gradle -v` in your terminal. If not, follow the link to the installation guide.

2. IntelliJ IDEA: Install the free IntelliJ IDEA Community Edition. It’s a great tool for working with Gradle projects.

## Step 1: Initializing the Project

Let’s get started by creating our project.

First, create a new directory called `plugin-tutorial` and navigate into it:

    $ mkdir plugin-tutorial
    $ cd plugin-tutorial

Now, run the `gradle init` command to automatically generate a basic plugin project. You can build this plugin in either Groovy or Kotlin:

    $ gradle init --type kotlin-gradle-plugin  --dsl kotlin

    $ gradle init --type groovy-gradle-plugin  --dsl groovy

When prompted for additional options, just accept the default values.

| All examples in this tutorial are based on a macOS environment.

## Step 2: Understanding the Project Layout

After `gradle init` finishes, you’ll have a new project structure. The `plugin-tutorial` directory is our root project, and inside, there’s a subproject named `plugin` where we’ll do most of our work.

The project should look like this:

    .
    ├── gradle                  (1)
    │   ├── libs.versions.toml  (2)
    │   └── wrapper
    ├── gradlew         (3)
    ├── gradlew.bat     (3)
    ├── settings.gradle.kts     (4)
    └── plugin/
        ├── build.gradle.kts    (5)
        └── src
            ├── main
            │   └── kotlin                    (6)
            │       └── org/example
            │           └── PluginTutorialPlugin.kt
            ├── test
            │   └── kotlin                    (7)
            │       └── org/example
            │           └── PluginTutorialPluginTest.kt
            └── functionalTest
                └── kotlin                    (8)
                    └── org/example
                        └── PluginTutorialPluginFunctionalTest.kt

1 | This folder holds the wrapper files that allow us to run Gradle without a local installation.
2 | This is a version catalog, a tool for managing all your project’s dependencies in one place.
3 | These are the Gradle wrapper scripts for macOS/Linux and Windows.
4 | This file defines the name of our build and includes our `plugin` subproject.
5 | The build script for our `plugin` subproject. This is where we’ll add our dependencies and configure the plugin.
6 | The default source folder for our new plugin.
7 | The default folder for unit tests.
8 | The default folder for functional tests.

    .
    ├── gradle                  (1)
    │   ├── libs.versions.toml  (2)
    │   └── wrapper
    ├── gradlew         (3)
    ├── gradlew.bat     (3)
    ├── settings.gradle     (4)
    └── plugin/
        ├── build.gradle    (5)
        └── src
            ├── main
            │   └── groovy                    (6)
            │       └── org/example
            │           └── PluginTutorialPlugin.groovy
            ├── test
            │   └── groovy                    (7)
            │       └── org/example
            │           └── PluginTutorialPluginTest.groovy
            └── functionalTest
                └── groovy                    (8)
                    └── org/example
                        └── PluginTutorialPluginFunctionalTest.groovy

1 | This folder holds the wrapper files that allow us to run Gradle without a local installation.
2 | This is a version catalog, a tool for managing all your project’s dependencies in one place.
3 | These are the Gradle wrapper scripts for macOS/Linux and Windows.
4 | This file defines the name of our build and includes our `plugin` subproject.
5 | The build script for our `plugin` subproject. This is where we’ll add our dependencies and configure the plugin.
6 | The default source folder for our new plugin.
7 | The default folder for unit tests.
8 | The default folder for functional tests.

## Step 3: Review the Gradle Build File

Let’s take a look at the `build.gradle(.kts)` file inside the `plugin` directory. This is where the magic happens.

When you’re writing a plugin, you’ll use the `java-gradle-plugin` to:

1. Automatically generate the necessary plugin metadata.

2. Add plugin development conventions and tasks.

3. Simplify the publishing process.

This is what the `gradlePlugin {}` and `plugins {}` block looks like:

plugin/build.gradle.kts

    plugins {
        // Apply the Java Gradle plugin development plugin to add support for developing Gradle plugins
        `java-gradle-plugin`
        // Apply the Kotlin JVM plugin to add support for Kotlin.
        alias(libs.plugins.kotlin.jvm)
    }

    gradlePlugin {
        // Define the plugin
        plugins.create("greeting") {
            id = "org.example.greeting"
            implementationClass = "org.example.PluginTutorialPlugin"
        }
    }

plugin/build.gradle

    plugins {
        // Apply the Java Gradle plugin development plugin to add support for developing Gradle plugins
        id 'java-gradle-plugin'
        // Apply the Groovy plugin to add support for Groovy
        id 'groovy'
    }

    gradlePlugin {
        // Define the plugin
        plugins {
            greeting {
                id = 'org.example.greeting'
                implementationClass = 'org.example.PluginTutorialPlugin'
            }
        }
    }

- `gradlePlugin {}`: This is where you configure the plugins you’re authoring.

- `val greeting by plugins.creating {}` or `plugins.greeting {}`: This registers a new plugin definition with the ID `org.example.greeting`.

- `implementationClass = "org.example.PluginTutorialPlugin"`: This points to the main class that contains your plugin’s logic.

## Step 4: Review the Plugin Code

The plugin code is a simple "Hello, World!" example that `gradle init` generated for us.

You can find it at `plugin/src/main/kotlin/org/example/PluginTutorialPlugin.kt`:

You can find it at `plugin/src/main/groovy/org/example/PluginTutorialPlugin.groovy`:

plugin/src/main/kotlin/org/example/PluginTutorialPlugin.kt

    package org.example

    import org.gradle.api.Project
    import org.gradle.api.Plugin

    /**
     * A simple 'hello world' plugin.
     */
    class PluginTutorialPlugin: Plugin<Project> {
        override fun apply(project: Project) {
            // Register a task
            project.tasks.register("greeting") { task ->
                task.doLast {
                    println("Hello from plugin 'org.example.greeting'")
                }
            }
        }
    }

plugin/src/main/groovy/org/example/PluginTutorialPlugin.groovy

    package org.example

    import org.gradle.api.Project
    import org.gradle.api.Plugin

    /**
     * A simple 'hello world' plugin.
     */
    class PluginTutorialPlugin implements Plugin<Project> {
        void apply(Project project) {
            // Register a task
            project.tasks.register("greeting") {
                doLast {
                    println("Hello from plugin 'org.example.greeting'")
                }
            }
        }
    }

- `Plugin<Project>`: Our plugin needs to implement this interface to work with a `Project` object.

- `apply()`: This method is the entry point. Gradle calls it when the plugin is applied to a project.

- `tasks.register("greeting")`: This is how we register a new task. Users can run it from the command line with `./gradlew greeting`.

- `doLast {}`: This block contains the code that runs when the task is executed.

## Step 5: Understand the Plugin’s Behavior

To see the plugin in action, you can apply the plugin using its ID (`org.example.greeting`) in a `plugins` block:

    plugins {
        id("org.example.greeting")
    }

After applying it, running the `greeting` task with `./gradlew greeting` will produce the following output:

    Hello from plugin 'org.example.greeting'

## Step 6: What we will Build

This tutorial will guide you in building a powerful Slack Notification Gradle Plugin. This plugin will make it easy to automatically report your build results to a Slack channel.

The finished plugin will be able to:

- Send a custom Slack message with a simple task (`sendTestSlackMessage`).

- Automatically report build success or failure at the end of the build.

- Integrate seamlessly with the build lifecycle using modern Gradle APIs like `FlowAction`.

## Step 7: Slack Client API Setup

To get started, you’ll need to set up the Slack API Client.

1. Get a Slack Account and Workspace:

   - Create a Slack Account.

   - Create a Slack Workspace where you have administrative privileges.

2. Create a Slack App:

   - Navigate to the Slack App creation page.

   - Select "Create An App" → "From Manifest" and accept the defaults to create a "Demo App".

3. Configure Permissions and Get Your Token:

   - Go to "OAuth & Permissions" in your app’s settings.

   - Under "Bot Token Scopes," click "Add an OAuth Scope" and select `chat:write`. This gives your app permission to post messages.

   - Select "Install App" to install it in your workspace.

   - A Bot User OAuth Token will be generated. It will start with `xoxb-`. Be sure to save this token! It’s what we’ll use to authenticate our plugin’s API calls.

You’re all set! Now you have a working Gradle plugin project and all the tools you need to connect to Slack.

Next Step: Add an Extension >>