Gradle is one of the new "cool kids on the block". It is quickly gaining momentum as projects like Hibernate and Spring migrate their build processes over to Gradle. Gradle can be considered the 3rd generation of Java build tools, with Ant and Maven representing the earlier generations.
Gradle is built on top of Groovy, which provides the ability to define a Domain Specific Language (DSL). In this case, the Gradle DSL provides a language tailored to the task of building code. If the DSL does not provide exactly what you need, then you can extend the DSL using plug-ins. It is possible to learn Gradle without knowing Groovy, but some initial knowledge of Groovy is beneficial.
This book is short (89 pages) . It brings back memories of the O'Reilly "A Developer's Notebook" series.
Chapter 1, Hello Gradle This chapter leads the reader thru the installation and configuration of Gradle and demonstrates the ubiquitous Hello World (build file) example.
Chapter 2, Gradle Tasks This is the best chapter in the book. It drives home the concepts associated with a 'task' and how the tasks can be configured and customized. The most helpful suggestion in the book is found in this chapter. The recommendation is that you read the Gradle DSL documentation. I had previously read the Gradle Users Guide but was still a bit fuzzy on what the properties and methods were and how they were used. . Reading the DSL documentation provides the full picture. It also helps drive home that you are working with a programming language/DSL and not a set of XML tags like Ant and Maven.
Chapter 3, Ant and Gradle This chapter compares and contrasts Ant and Gradle. It also demonstrates that Gradle can run Ant tasks by importing an Ant build.xml or by using the Ant Builder that is part of the Groovy distribution.
Chapter 4, Maven and Gradle This is the longest chapter in the book comprising about 25% of the book. Like all of the Gradle documentation, this book re-assures the reader that any previous investment in Maven or Ivy will not be lost in a move to Gradle. Gradle provides support for Ivy, Maven's Central repository and a local repository.
Chapter 5, Testing with Gradle This chapter is a good overview of using JUnit , TestNG, Spock, Geb and EasyB. Coverage of testing is a bit light given the title of this book.
Chapter 6, Multiproject Builds This chapter does a nice job of taking a sample project and showing three different approaches to creating the project build structure. The approaches shown are one master build file, project-specific build files and a hybrid approach. While the sample projects are very small, they provide the reader a starting point to converting their own multiproject builds.
This is an excellent book for getting started with Gradle. There are plenty of working examples provided in the source code download package. The authors do a very good job of explaining the concepts and presenting alternative ways of expressing the same options within the DSL.
One minor issue is that matching up the downloaded source examples to the examples in the printed chapters is a bit of an exercise because they are not organized in a folder structure by chapter like many other books.
Initially the slim size of the book worried me as to it's ability to provide a depth of coverage of Gradle, but the authors stated in the Preface that "Future volumes will cover the Gradle plug-in ecosystem, how to extend Gradle with your own business logic and even more advanced topics." Sounds good to me, bring it on Tim and Matthew!