Slurp.. technical blogs!: OSGi Bundle States in AEM

Sunday, April 24, 2022

OSGi Bundle States in AEM

OSGi is a fundamental element in the technology stack of AEM. It is used to control the composite bundles of AEM and their configuration. OSGi “provides the standardized primitives that allow applications to be constructed from small, reusable and collaborative components.

OSGi

OSGi is a Java framework for developing and deploying modular software programs and libraries. OSGi has two parts.

Bundles or Plug-in
Java Virtual Machine (JVM)-level service registry.

In this article, we will focus on bundle states only.

A Bundle object is the access point to define the lifecycle of an installed bundle. Each bundle installed in the OSGi environment must have an associated Bundle object.

A bundle must have a unique identity, a long, chosen by the Framework. This identity must not change during the lifecycle of a bundle, even when the bundle is updated. Uninstalling and then reinstalling the bundle must create a new unique identity.

A bundle can be in one of six states:

Name	Value	Description
UNINSTALLED	0x00000001	Only visible after a bundle is uninstalled; the bundle is in an unusable state but references to the bundle object may still be available and used for introspection.
INSTALLED	0x00000002	Visible if the bundle’s code dependencies are not resolved. The Framework may attempt to resolve an INSTALLED bundle’s code dependencies and move the bundle to the RESOLVED state.
RESOLVED	0x00000004	The Framework has successfully resolved the bundle’s code dependencies, but the bundle is not active. Dependencies include: the bundle’s classpath; the bundle’s package dependencies; the bundle’s required bundle dependencies;
STARTING	0x00000008	The bundle’s start method is active. A bundle must be in this state when the bundle’s BundleActivator.start(BundleContext) is called. If the BundleActivator.start method completes without exception, then the bundle has successfully started and must move to the ACTIVE state.
STOPPING	0x00000010	The bundle’s stop method is active. A bundle must be in this state when the bundle’s BundleActivator.stop(BundleContext) method is called. When the BundleActivator.stop method completes the bundle is stopped and must move to the RESOLVED state.
ACTIVE	0x00000020	The bundle has been successfully started and activated.