Eclipse Gemini Blueprint project makes it easy to build Java applications that run in an OSGi framework. By using Gemini Blueprint, applications benefit from using a better separation of modules, the ability to dynamically add, remove, and update modules in a running system, the ability to deploy multiple versions of a module simultaneously (and have clients automatically bind to the appropriate one), and a dynamic service model.
Eclipse Gemini Blueprint is the reference implementation for the <a href="http://www.osgi.org">OSGi Alliance</a> Blueprint Service (chapter 121 of the OSGi 4.2 Compendium Specification).