Grails in Action [ペーパーバック]

I've read both this book and the older Definitive Guide to Grails, Second Edition, and I'm happy to report that Grails in Action is both more concise and better-organized than that other (nonetheless excellent) tome. It is also slightly cheaper and, until Grails 1.2 is released (it's in early milestone as of this writing, so I wouldn't expect it to be production-ready before 2010), pleasingly up-to-date. There are very few errors, and if you find any, the authors will be happy to help you sort them out in the book's official forum.

The book's great strength is its organization. There's all kinds of online documentation for Grails, including a decent reference manual at grails.org, but searching through the mailing lists and the JIRA when the framework does something unexpected is no fun at all. Grails in Action starts off right with a primer on Groovy (which I found refreshing, even though I've read Groovy in Action), then jumps into practical Grails concepts, which it teaches by example. (The central project of the book, a low-budget Twitter clone, is an excellent showcase for Grails.) The later chapters introduce advanced concepts that are extremely useful but not covered (or not covered well) in Grails' documentation. For example, Chapter 13 tells you how to improve database performance by setting up and enabling EhCache; how to use p6spy and sqlprofiler to easily time your database queries; and how to migrate your database using Liquibase. Other chapters talk about concepts like REST and JMS with surprising clarity.

Whether you're a beginner or an experienced Grails developer, I'd say that this is the only Grails book you need.

I've been following Groovy and Grails books for a couple years now, and own nearly all of them. Each one has filled a niche, and almost all have been great in letting the voice of the authors come through while keeping the style of the publisher (Manning books have a different feel from Apress, for example).

I had high hopes for this book, and wasn't disappointed. It had tough competition from the recent The Definitive Guide to Grails, Second Edition (Expert's Voice in Web Development) but I think this book *slightly* edges out that one as a Grails resource. Why? It's slightly more up to date, for starters. The chapters on dealing with legacy databases and on adding security to an app were both a bit more informative, or at least I found them a bit easier to follow. This is not to detract from the DGG. If you *can*, I'd recommend owning both, as each presents similar information in a unique style. The Grails in Action book feels somewhat more conversational, which made the reading easier for me.

There's a lot more substance other reviewers have given on this book - I'm not sure I'm going to go in to as much detail as they have. Suffice it to say that this is currently my book of choice for working with Grails these days. Glen and Peter have packed an incredible amount of information in to 500 pages, with concise writing, useful examples, and just enough humor to keep it entertaining without losing its utility.

For most of 2008, I was recommending Beginning Groovy and Grails: From Novice to Professional (Beginning from Novice to Professional) from Christopher Judd and company. For my money it was *the* book for 2008 for Grails developers. I think given the advances in the past several months, both the new DGG and this new Grails In Action book deserve to share the title of "Best Grails Book". You can't go wrong with either book.

As an aside, I'd also recommend Groovy and Grails Recipes from Bashar Abdul-Jawad if you're looking for a companion piece to Grails In Action. It provides a 'recipe' approach to quickly finding the code snippets you need to solve a particular problem.

I've written this review on my blog, reproducing it here:
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The book is organized into four parts:
* Introduction: The very first chapter is aptly titled as `Grails In a Hurry'. If you are a complete beginner to Grails you will be blown away with the productivity and the powerful feature set of Grails on display. Many concepts explained in detail in the later chapters are summarized with a simple example. Second chapter goes over Groovy basics, which is adequate.
* Fundamentals: I think taking up a non-trivial example to explain the concepts of a framework is nice. A Twitter-like application is built during the course of this part of the book. This part explains about using GORM (Grails Object Relational Mapping Library), techniques for using Constraints for validation, power of Grails scaffolding, usage of dynamic queries, controlling application flow and the usage of services, introduction to GSPs and the discussion about views and layouts (along with AJAX stuff).
* Building more features into your applications: How well different levels of testing (unit, integration, functional) are integrated into the framework is discussed. This part then continues with the basics of plugins and their usage. One of my favorite chapters in this book follows next, workflow with Grails Webflow. Security is discussed in some detail, but the chapter that follows really stands out (especially for a huge REST fan like me) -- explains how to design and implement a RESTful API showcasing Grails support for this architectural pattern.
* What you need to know for real work: The last part of the book explains about -- messaging and scheduling, some advanced GORM concepts, how to use Spring and transactions with Grails, and about plugin development. The chapter on advanced GORM concepts is well written; folks who intend to use Grails for enterprise-level applications will certainly benefit from this chapter.

This is my first formal reading of a Grails book, but have some decent exposure to the concepts of Grails (from the available documentation, and by the presentations that I attended in the past). So for me, introductory chapters and some of the fundamentals are well-needed refreshers, but the last two parts really stand out. Some points from my notes:
* For integration tests, Grails bootstrap the database and wires up all components just as it would for a running web app.
* Domain class relationships (1:1, 1:M, M:N) are explained quite well from the Grails point of view -- belongsTo variations, hasMany and GORM magic of automatically adding new methods to account for the defined relationships.
* Groovy querying with dynamic finders: Dynamic finders take advantage of funky Groovy metaclass magic to intercept all method calls on a domain object; leverages Groovy's methodMissing feature.
* Use flash scope for passing messages to the user when a redirect is involved.
* Extensive discussion on the Grails form taglibs, and on creating your own tags.
* Mocking is built-in the framework for productive unit testing.
* Webflow introduces a new scope: flow scope. Items put in flow scope live for the life of the flow. Favor flow scope over session scope -- Webflow will cleanup the storage for you and give you more efficient server memory.
* The chapter on implementing the REST architectural pattern is a must read; Grails supports the pattern out-of-the-box.
* Grails uses OSCache as its default cache library (for Hibernate's second-level cache). The reason suggested was that it plays well with Grails developer restarts, something I would like to understand further in reference to Ehcache. But the authors actually used Ehcache in the book suggesting that it is a better library (I agree!).
* So easy to declare caching at the domain level:
static mapping = {
cache: "read-write"
}
* Discussion on integrating with legacy databases is interesting, but would like to see some case studies to understand the real pain involved.
* Transactional services are implemented using Spring's AOP mechanism (Spring's TransactionProxyFactoryBean).
* Integration tests run inside a transaction by default, which is then rolled back after each test finishes. This ensures that data changes don't affect other tests, but it means you can't check whether transactions are rolled back or not. If you want to test transactional behavior then you need to add a static transactional property to your test.

Conclusion
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The book is very well organized and the topics chosen are well thought of. An easy conversational tone is used through out the book. In my opinion, this book succeeds in building a sustained interest about the framework. It is also an excellent reference book on the topic. Strongly recommend the book for all Grails enthusiasts.