Gradle Multi-Project Builds — Organizing and Scaling Your Projects

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Introduction

Gradle is a powerful build automation tool that enables developers to manage the build process of various types of projects. One of its key features is the ability to support multi-project builds. This feature simplifies the build process when working with large-scale projects or codebases that consist of multiple subprojects.

In this article, we’ll explore Gradle multi-project builds, how to organize and scale your projects, and provide some code examples to help you understand the concepts better.

Understanding Gradle Multi-Project Builds

A multi-project build is a single build that encompasses multiple subprojects. Each subproject can have its own build.gradle file and dependencies. This structure allows you to manage and build subprojects independently or as a group, depending on your needs.

Setting Up a Multi-Project Build

To set up a multi-project build, you’ll need to create a root project folder with a ‘settings.gradle’ file. This file will include the subprojects and their relative paths.

Example settings.gradle:

rootProject.name = 'MyMultiProject'
include 'subproject1'
include 'subproject2'

Each subproject should have its own build.gradle file to define its build configuration and dependencies.

Example subproject1/build.gradle:

plugins {
    id 'java'
}

dependencies {
    implementation 'com.google.guava:guava:30.1-jre'
}

repositories {
    mavenCentral()
}

Managing Common Configuration

You can manage common configuration settings, such as repositories and dependencies, in the root project’s build.gradle file. This helps to reduce duplication across subprojects and ensure consistency.

Example build.gradle:

allprojects {
    repositories {
        mavenCentral()
    }
}

subprojects {
    apply plugin: 'java'

    dependencies {
        testImplementation 'junit:junit:4.13.1'
    }
}

Executing Tasks Across Subprojects

You can execute tasks across all subprojects or selectively. To execute a task across all subprojects, run ./gradlew <taskName> from the root project directory.

For example:

./gradlew test

To execute a task in a specific subproject, run ./gradlew :subproject1:<taskName>.

For example:

./gradlew :subproject1:test

Dependency Management Between Subprojects

In a multi-project build, subprojects can depend on each other. You can declare these dependencies in the build.gradle file of the dependent subproject.

For example, if subproject2 depends on subproject:

dependencies {
    implementation project(':subproject1')
}

Conclusion

Gradle multi-project builds are an excellent way to manage and scale large projects with multiple subprojects. By understanding how to set up and configure these builds, you can streamline your development process and ensure consistency across your projects.

• The official Gradle user guide on multi-project builds

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