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. OSGi Architecture Bundles: JAR files with manifest Services: Connects bundles Services Registry: Management of services Modules: Import/export interfaces for bundles Possible to “wrap” existing Java apps and JARs Add additional manifest info to create OSGi bundle E.g.: Jetty web server now ships with OSGi manifest; now extensively used with OSGi containers and custom bundles For NetServ, we created a OSGi bundle for the Muffin HTTP proxy server Image credit: Wikipedia

3. Why OSGi? Why not just JAR files?

4. More than just JAR files; much richer encapsulation, metadata in manifest

5. Automatic dependency resolution

6. Version management

7. Provides systems services (logging, configuration, user authentication, device access, etc)

9. Eclipse Equinox, Apache Felix, Knoplerfish

10. Real-world examples

11. Eclipse IDE uses OSGi for plugin architecture

12. Mostly finds use in enterprise applications needing plugin functionality

13. E.g.: IBM Websphere, SpringSource (now VMWare) dm server, Red Hat's JBoss