This book is a step-by-step beginner's guide based on developing a case study (a book inventory) that walks the developer through the implementation while progressively explaining the surrounding concepts in context. Throughout the book, the author discusses software design concepts and introduces productivity tools that build up the reader's knowledge-base. This book is aimed at Java developers looking to learn about writing reusable and network distributable software following the OSGi standards using the famous Felix framework. If you are a developer who wants to focus on the business logic, and abstract away from the details of how to integrate with specific systems then this book is meant for you. If you are a Java developer new to OSGi and don't really know where to start from to actually begin developing applications, just pick up this book and discover the ease with which you can start developing powerful, modular, and extensible applications. This book uses the Felix framework 3.0 as an OSGi service platform implementation and covers its usage to a level where it makes you comfortable enough to write your own enterprise-level applications.