Gradle Beyond the Basics

Chapter 1. File Operations

If the most essential operation in a build is to compile code, then surely the second most essential operation is to copy files. A real-world build routinely copies files from place to place, recursing directory trees, pattern-maching filenames, and performing string operations on file content. Gradle exposes a few methods, task types, and interfaces to make file operations flexible and easy. Collectively, these form Gradle’s file API.

To explore the file API, we’ll start with practical examples of how to use the Copy task. We’ll move from there to an exploration of the file-related methods of the Project object, which are available to you anywhere inside a Gradle build. In the process, we’ll learn about the FileCollection interface. Finally, we’ll look at the ways the file API is used by common Gradle plug-ins—giving us a richer view of otherwise taken-for-granted structures like JAR files and SourceSets.

Copy Task

The Copy task is a task type provided by core Gradle. At execution, a copy task copies files into a destination directory from one or more sources, optionally transforming files as it copies. You tell the copy task where to get files, where to put them, and how to filter them through a configuration block. The simplest copy task configuration looks like Example 1-1.

Example 1-1. A trivial copy task configuration

task copyPoems(type: Copy) {
  from 'text-files'
  into 'build/poems'
}

The example assumes there is a directory called text-files containing ...