Ken Kousen - Making Java Groovy

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To my father, Morton Kousen, MD, who taught me everything I know about dedication, persistence, and facing the future with a positive and upbeat attitude, despite whatever pain and difficulties lay ahead. He will always be my best example of what a man should be.

When we designed the Groovy language almost 10 years ago, our main goal was to create a language that is a complement to Java, a close companion, that Java developers would be familiar with and could learn easily. The idea was to empower users to be more productive by removing the boilerplate of Java, and to simplify their programming lives by giving them compelling and straightforward APIs to work with. Im proud to say that the Groovy team attained that goal, making Groovy the most popular alternative language for the Java platform.

Along the way, and by virtue of its nature, Groovy was adopted by Java developers in a number of ways. For example, it was introduced in Java projects for testing purposes, because the Groovy syntax is light and readable but still resembles that of Java. For interacting with XML payloads, web services, or databases, Groovy provides handy and elegant wrappers around the Java Development Kit that make those tasks a breeze. And for writing business rules in Java applications, Groovy shines, thanks to its metaprogramming capabilities and its concise and expressive grammar.

I had the pleasure and honor of meeting Ken a few years ago at a Groovy conference, and our paths have crossed several times since then. Among other topics, we talked about how Groovy is a great fit for various assignments that Java developers have to accomplish every day but that are painful with the heavier-weight Java. So when Ken told me that he envisioned writing a book on this same topic, I was excited about the idea!

What makes this book stand out of the pack of Groovy books is its focus on the tasks that Java developers must tackle every day. How can I more easily parse or emit XML or JSON documents? How can I test my Java code with a more expressive syntax? How can I talk to my database without the error-prone JDBC API? How can I build and test Java applications more efficiently? In this book, Ken answers all of these questions and shows you a Groovy solution for each of those chores.

G uillaume L aforge
G ROOVY P ROJECT M ANAGER

A few months ago I enjoyed a pleasant dinner with Marjan Bace, Grand Poobah[] Some publishing companies strongly recommend that their books follow that model, with the reader as hero.

His actual title is Publisher.

In print form, on a tablet, or whatever.

In case you dont want to read the original Campbell, the Wikipedia page at http://en.wikipedia.org/wiki/Monomyth summarizes all 17 (!) stages.

Marjans idea, however, was that sometimes it isnt the reader who is the hero; its the technology covered by the book. In the case of Making Java Groovy, I interpret that to mean that Groovy is the hero. Where does that put Java? Not as antagonist, surely; the whole point of this book is that Java is already your ally, and that adding Groovy makes it better. Groovy and Java are like Frodo and Samwise Gamgee, headed into the black depths of Mordor, battling privation and despair, desperately trying to defeat the horrible programming challenges that await them, as well as any orcs, Nazgl, or clueless managers they might encounter along the way.

Thats a little dark. Plus, I have no idea what the Ring of Power is in this analogy, or why youd want to destroy it.[] Instead, Ill simply say that Groovy and Java work really, really well together, and Ill spend the rest of the book demonstrating how, when, and why.

I do hope that if youre holding a print copy of the book (that is, dead-treeware), no Ents were involved.

For those of you shifting nervously from side to side, worried that the attempts at humor in this preface will be sprayed liberally throughout the book (thus distracting from the actual content), let me assure you that other than in this preface, I promise to confine any attempts at humor to footnotes that can be safely skipped.[]

Like this one: How many developers does it take to change a light bulb? The classic answer is, None; thats a hardware problem. My answer is, The developer is the person by the light switch saying, Maybe this time the light will go on. Or maybe this time. Reboot again.

When Im teaching my technical training classes,[

Seriously, Best Training Anywhere. Contact me for a quote, which will inevitably rise once this book is published.

I was going to make a DRYDont Repeat Yourselfjoke here but eventually decided against it.

The source code for the book is available in my GitHub repository.[] If you examine it, youll find more examples than the ones covered in the book. Books have length limits, but source code repositories dont, and extra examples cant hurt. I decided to use the books repository as a home for any examples I felt were interesting or relevant, even if I couldnt justify the extra pages necessary to discuss them.

Check it out at https://github.com/kousen/Making-Java-Groovy.

Again, keeping to the principle that the chapters should be as independent as possible, each project has its own Gradle build file.[] All the examples have tests as well. The short snippets of code include Groovy assert statements, and test cases are used to execute the scripts during a build. The rest of the examples have a mix of JUnit tests, in Java or Groovy, and Spock tests. In practice I freely intermix both, so it seemed natural to do so here, too.