To enable components to be added when required, GlassFish Server provides a lightweight and extensible kernel that uses the module management subsystem from the OSGi Alliance. Any GlassFish Server component that plugs in to this kernel must be implemented as an OSGi bundle. To enable an add-on component to plug in to the GlassFish Server kernel in the same way as other components, package the component as an OSGi bundle. For more information, see Packaging an Add-On Component.
The default OSGi module management subsystem in GlassFish Server is the Apache Felix OSGi framework. However, the GlassFish Server kernel uses only the OSGi Service Platform Release 4 API. Therefore, GlassFish Server supports other OSGi module management subsystems that are compatible with the OSGi Service Platform Release 4 API.