Gradle Beyond the Basics

Chapter 3. Build Hooks

By itself, Gradle is a deeply customizable toolkit for creating custom build software. It comes with out-of-the-box conventions that are useful for highly standardized builds, and it exposes a rich set of APIs for introducing novel functionality into a non-commodity build as we saw in Chapter 2. But your ability to customize a Gradle build doesn’t end with plug-ins.

Gradle offers you the ability to modify the execution of that program by hooking a variety of events that occur during the configuration and execution of your build. These hooks are simply blocks of Groovy code that run when tasks are added, when projects are created, and at other times during Gradle’s internal configuration sequence. Also, following the patterns implicit in Groovy’s own metaprogramming APIs, Gradle gives you the ability to create tasks dynamically based on its powerful rules feature. This chapter presents hooks and rules as a means of managing build complexity and decorating the functionality of builds whose source we do not always directly control.

The Gradle Lifecycle: A Review

Many readers of this book will be familiar with the Gradle build lifecycle, but a thorough understanding of build hooks requires that we revisit it briefly. Every Gradle build proceeds through three lifecycle phases in precisely the same order. These phases are initialization, configuration, and execution.

During the initialization phase, Gradle starts up and locates the build files it must process. Crucial ...