Monday, June 8, 2009

JBoss Drools Business Rules book review

It's quite difficult to get started with Drools, especially if you don't have experience in developing Java applications. You might imagine how steep the learning curve is for business analysts, who associates Java with an island or coffee. However this book is aimed at exactly this group of non-technical people, who have knowledge how business runs, but don't know how or simply don't have the tools to persist it and 'transfer it to the world of computers'.

Most chapters are kept on a really basic level if it comes to writing Java code. On the other hand it's sufficient to get started. Moreover all used tools are open source software, which means you can use it for free.

This book goes through almost all parts of Drools, especially the most important for business people like Guvnor, the application for authoring rules, DSLs allowing to write rules in plain English as well as support for the business analyst's most favorite tool: Excel spreadsheets.

The author even introduces typical developers' tools like Eclipse, however I would recommend to go through an updated guide about installing the Eclipse plugin available in the Drools docs. A new requirement, that did not make it into this book, is to set up the Drools rule engine.

There's a chapter I like very much. It makes very clear that testing rules is an important part of the development cycle and introduces three different ways to achieve full coverage of all written rules. The inquisitive reader might also have a look at the QA Analyzer, a quite new and powerful feature available in Guvnor.

One chapter is definitely intended for Java developers - about deploying Drools applications in real world scenarios. The business people will still be able to follow, since the author keeps things easy and doesn't go to deep into details, however I would love to read more about this topic.

The last two chapters about rule engine concepts and the newest features are a must-read for all those people who have read the Drools docs, but still need a different point of view to fully understand how Drools works. This topic is very important in my opinion, since it lets you write your rules more effectively.

What I didn't like was the use of IE and Excel. Same results could be achieved with open source software, too. But that's a minor one ;)

All in all, definitely a guide for non technical users, but also for developers, who have given the Drools docs a (second and third) try and still require a helping hand to sort it out how this Drools thing works and how to use it properly.

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