Automatic Uninstalling of Prerequisite Bundles

When a bundle with prerequisite SAT bundles is uninstalled, SAT can automatically uninstall the prerequisite SAT bundles if they do not have any other dependent bundles.

By default SAT bundles are not candidates for being automatically uninstalled. An SAT bundle indicates that it can be automatically uninstalled by overriding the BaseBundleActivator configuration parameter method isUninstallable() to answer true.

Any SAT bundle that overrides the configuration parameter method isUninstallable() to answer true is a candidate for being automatically uninstalled.
Whenever any bundle is uninstalled, whether it is an SAT bundle or not, candidate prerequisite SAT bundles will automatically be uninstalled when they no long have any dependents.
Code-only SAT bundles can also be automatically uninstalled, but they must have a bundle activator that is a subclass of BaseBundleActivator so they can override the configuration parameter method isUninstallable() to answer true.
No special uninstall command is necessary. Internally SAT is an OSGi framework BundleListener, so when it hears that a bundle has been uninstalled its prerequisite SAT bundles will be automatically uninstalled if they do not have any dependent bundles.

For example, consider the puzzle piece diagram:

Code-only bundles usually do not need bundle activators, but since the Vendor Service bundle wishes to be automatically uninstallable, it has a bundle activator that overrides the method isUninstallable() to answer true.
Both the Hotdog Vendor bundle and the Popcorn Vendor bundle wish to be automatically uninstallable, so they have bundle activators that override the method isUninstallable() to answer true.
The Customer bundle is a leaf since it is at the top of the bundle food chain. Leaf bundles are typically not automatically uninstallable since they don't have dependents. The Customer bundle inherits from the BaseBundleActivator the method isUninstallable() that returns false.

At runtime the Customer bundle acquires the VendorService from either the Hotdog Vendor bundle or the Popcorn Vendor bundle. For the purpose of this example we shall assume that the Customer bundle acquires the Hotdog Vendor bundle's implementation of the VendorService.

When the Customer bundle is uninstalled SAT attempts to automatically uninstall its prerequisite bundles:

The Hotdog Vendor bundle is automatically uninstalled since it has no dependents.
The Vendor Service bundle is not automatically uninstalled since it has the Popcorn Vendor bundle as a dependent.

Having uninstalled the Customer bundle, the Popcorn Vendor bundle and Vendor Service bundles remain. When the Popcorn Vendor bundle is uninstalled SAT attempts to automatically uninstalls its prerequisite bundles:

SAT automatically uninstalls the Vendor Service bundle since it has no dependents.