Book Review: Programming Groovy

In the movie 2001, A Space Odyssey, the director Stanley Kubrick spends a vast amount of time with lava lamp-style special effects. The last part of the movie is an interminable journey through the same scene with different colors. Kubrick would never make that movie now: at least a third would end up on the cutting room floor. But he was entranced with the shiny new technology and indulged it to distraction.

The same thing tends to happen when a new technology comes out. If you are an early adopter, you'll slog through the lava-lamp effects to get to the meat of the new technology. Groovy has followed this route. Because I've been following Groovy for a while, most of the previous Groovy books have been in two categories:

• wow, look at this new thing! Isn't it cool that you can do all this stuff, which contains useful information but also a fair amount of "look, she's walking upside down for 10 minutes" kind of stuff


• recipes for getting real work done (where Groovy Recipes falls, so I think it's very well named. I reviewed it just before this one.)
  

I don't mean for this list to sound pejorative: every new technology comes out with these books first: it's an inevitable part of the technology life-cycle for new languages. But eventually someone comes out with a book that no longer treats the new language like a shiny new thing, but as a serious contender in the language universe. And that's Programming Groovy by Venkat Subramaniam (disclaimer: I know Venkat, but you shouldn't hold that against him). It doesn't treat Groovy like a novelty act. It also doesn't provide recipes. Instead, it treats Groovy as a real programming language. I'll have to admit, this is the Groovy book for which I've been waiting.

Groovy is friendlier syntax for programming Java (I called it the real JDK here). Books about the practical aspects of Groovy are very important because, as a language, it resides in a unique place: it's a low impedance way to program the Java platform, and it displaces Java for lots of common tasks. But it is also a powerful language in its own right. Programming Groovy has 4 chapters on meta-programming Groovy, and another long chapter on building domain specific languages. That's meaty stuff. It never condescends or makes excuses for Groovy but treats it like a real language. It includes lots of material that's hard to find online (like how ExpandoMetaclass really works). This is going to be both a classic in the Groovy literature and an exemplar for describing the real power of new languages.