OSGi is a dynamic module system for Java that allows bundles (JAR files with manifests) to be installed, started, stopped, updated, and uninstalled without requiring a reboot. Bundles export and import packages through an extensible services registry that supports automatic dependency resolution and version management. Existing Java applications and libraries can be wrapped as OSGi bundles by adding manifest information. For example, the Jetty web server and Muffin HTTP proxy server were packaged as OSGi bundles.

1. OSGiArchitectureBundles: JAR files with manifestServices: Connects bundlesServices Registry: Management of servicesModules: Import/export interfaces for bundlesPossible to “wrap” existing Java apps and JARsAdd additional manifest info to create OSGi bundleE.g.: Jetty web server now ships with OSGi manifest; now extensively used with OSGi containers and custom bundlesFor NetServ, we created a OSGi bundle for the Muffin HTTP proxy serverImage credit: Wikipedia

2. OSGi“Dynamic module system for Java” - website

3. Why OSGi? Why not just JAR files?