Part 3. Case studies

A picture is worth a thousand words. Examples of Lucene truly “in action” are invaluable. Readers of the first edition of this book loved the case studies chapter, so we’ve solicited a new set of case studies from the Lucene community for this new edition of the book. Lucene is the driving force behind many applications. There are countless proprietary or top-secret uses of Lucene that we may never know about, but there are also numerous applications that we can see in action online. Lucene’s wiki has a section titled PoweredBy, at http://wiki.apache.org/lucene-java/PoweredBy, which lists many sites and products that use Lucene.

Lucene’s API is straightforward, but the real magic happens when it’s used cleverly. The case studies that follow are prime examples of intelligent uses of Lucene. Read between the lines of the implementation details of each and borrow the gems within. The study from Krugle.org, in chapter 12, shows several tricks they used for smart source code indexing and searching but that could be applied to situations other than source code. Chapter 13 describes SIREn, a set of Lucene extensions that enable efficient search on the semantic Web, also known as Web 3.0. SIREn makes heavy use of Lucene’s extension points and is a great demonstration of what can be done using payloads (see section 6.5). Finally, chapter 14 describes two useful extensions to Lucene, the Bobo Browse faceted search system and the Zoie real-time search system.

If you’re new to Lucene, read these case studies at a high level and gloss over any technical details or code listings; get a general feel for how Lucene is being used in a diverse set of applications. If you’re an experienced Lucene developer or you’ve digested the previous chapters in this book, you’ll enjoy the technical details; perhaps some are worth borrowing directly for your applications.

We’re enormously indebted to the contributors of these case studies who took time out of their busy schedules to write what you see in the following chapters, but also to Lucene developers and numerous contributors who made it possible to build such a varied spectrum of search-related applications on top of the powerful yet flexible Lucene foundation.