Gradle overview

Before getting into the details of Gradle, we need to understand some of the terminologies related to the build system.

There are two types of build tools, namely imperative build tools and declarative build tools. An imperative build tool tells the system what to do and how to do it. In other words, it provides a set of action statements or commands, which the system executes in the same order and performs those actions. You can take Ant as an example of the imperative build system.

Whereas, a declarative build tool instructs the system, telling it what you would like to achieve, and system will figure out how to interpret it. With a declarative approach, the user only needs to determine the what, not the how. This is one of the key innovations Maven brought to the build world, after Ant achieved some popularity, where we don't need to write each and every step of an action, and end up creating a very large and verbose build script. With Maven we need to write some configuration parameters for the build and the build system itself decides how to interpret it. Internally, the declarative layer is based on a powerful imperative layer, which can be accessed directly as required. Ant and Maven are very good and reliable build systems. They are innovative in all the areas for which they were designed and built. Each of them has introduced key innovations into the build space.

Gradle combines the good parts of both tools and provides additional features and uses Groovy as a Domain Specific Language (DSL). It has power and flexibility of Ant tool with Maven features such as build life cycle and ease of use.

Gradle is a general purpose, declarative build tool. It is general purpose because it can be used to build pretty much anything you care to implement in the build script. It is declarative, since you don't want to see lots of code in the build file, which is not readable and less maintainable. So, while Gradle provides the idea of conventions and a simple and declarative build, it also makes the tool adaptable and developers the ability to extend. It also provides an easy way to customize the default behavior and different hooks to add any third-party features.

Primarily, Gradle is a JVM-language build tool, but it also supports C, C++, Android, and so on. You will find more information about this at https://docs.gradle.org/current/userguide/nativeBinaries.html.

It provides automation for the different phases required in a Java project, such as compile, package, execute test cases, and so on. It has grouped its similar automation tasks into plugins. When you import any plugin to a Gradle script file, they always come with a set of predefined tasks. To get started with Gradle, you need to have basic knowledge of Java. It uses Groovy as its scripting language, which is another JVM language. We will discuss Groovy in the next chapter. As the build script is written in Groovy, it tends to be much shorter, expressive, and clearer than those written in Ant or Maven. The amount of boilerplate code is much less in Gradle with use of Groovy DSL. It also leverages Maven conventions for familiarity, while making it easy to customize to the needs of your project. Developers can add new functionality or extend the existing features at any time. They can override the existing tasks or plugins to provide the new functionality.