Launching and embedding an OSGi framework - OSGi in Action - page 420

1 If the framework isn't in the Bundle.STARTING state, the init() method is
invoked.
2 The framework sets its beginning start level to the configured value, which
causes all reloaded bundles to be started in accordance with their activation
policy and start level.
3 The framework's state is set to Bundle.ACTIVE .
4 A framework event of type FrameworkEvent.STARTED is fired.
You may wonder why the init() method is necessary and why all the steps aren't per-
formed in the start() method. In some cases, you may want to interact with the
framework instance before restarting cached bundles, but some interactions can only
happen via the framework's BundleContext object. Because bundles (including the
framework) don't have a BundleContext object until they've been started, init() is
necessary to transition the framework to the Bundle.STARTING state so you can
acquire its context with Bundle.getBundleContext() .
To summarize, in the normal case, call start() . But if you want to perform some
actions before all the cached bundles restart, call init() first to do what you need to
do followed by a call to start() . When the framework is active, subsequent calls to
init() and start() have no effect.
Next, we'll look at how you shut down a running framework.

13.1.5 Stopping a framework instance

As you may guess, stopping an active framework involves invoking the stop()
method inherited from the Bundle interface. This method asynchronously stops the
framework on another thread, so the method returns immediately to the caller. If
you want to know when the framework has finished shutting down, call Framework.
waitForStop() after calling stop() , which blocks the calling thread until shutdown
is complete.
The following steps are performed when you stop a framework:

The framework's state is set to Bundle.STOPPING .

1

All installed bundles are stopped without changing each bundle's persistent
activation state and according to start levels.

2

The framework's start level is set to 0. 3

Framework event handling is disabled.

4

The framework's state is set to Bundle.RESOLVED . 5

All resources held by the framework are released. 6

All threads waiting on Framework.waitForStop() are awakened. 7

NOTE Calling waitForStop() doesn't start the framework shutdown process,
it waits for it to occur. If you want to stop the framework, you must call stop()
on it first.