Knopflerfish OSGi 5.2.0

org.osgi.framework
Interface ServiceFactory<S>

Type Parameters:
S - Type of Service
All Known Implementing Classes:
XMLParserActivator

public interface ServiceFactory<S>

Allows services to provide customized service objects in the OSGi environment.

When registering a service, a ServiceFactory object can be used instead of a service object, so that the bundle developer can gain control of the specific service object granted to a bundle that is using the service.

When this happens, the BundleContext.getService(ServiceReference) method calls the ServiceFactory.getService method to create a service object specifically for the requesting bundle. The service object returned by the ServiceFactory is cached by the Framework until the bundle releases its use of the service.

When the bundle's use count for the service is decremented to zero (including the bundle stopping or the service being unregistered), the ServiceFactory.ungetService method is called.

ServiceFactory objects are only used by the Framework and are not made available to other bundles in the OSGi environment. The Framework may concurrently call a ServiceFactory.

Version:
$Id: 535776e702ec5ace54f577218ff8f7920741558b $
See Also:
BundleContext.getService(ServiceReference)
ThreadSafe

Method Summary
 S getService(Bundle bundle, ServiceRegistration<S> registration)
          Creates a new service object.
 void ungetService(Bundle bundle, ServiceRegistration<S> registration, S service)
          Releases a service object.
 

Method Detail

getService

S getService(Bundle bundle,
             ServiceRegistration<S> registration)
Creates a new service object.

The Framework invokes this method the first time the specified bundle requests a service object using the BundleContext.getService(ServiceReference) method. The service factory can then return a specific service object for each bundle.

The Framework must check that the returned service object is valid. If the returned service object is null or is not an instanceof all the classes named when the service was registered, a framework event of type FrameworkEvent.ERROR is fired containing a service exception of type ServiceException.FACTORY_ERROR and null is returned to the bundle. If this method throws an exception, a framework event of type FrameworkEvent.ERROR is fired containing a service exception of type ServiceException.FACTORY_EXCEPTION with the thrown exception as the cause and null is returned to the bundle. If this method is recursively called for the specified bundle, a framework event of type FrameworkEvent.ERROR is fired containing a service exception of type ServiceException.FACTORY_RECURSION and null is returned to the bundle.

The Framework caches the valid service object and will return the same service object on any future call to BundleContext.getService for the specified bundle. This means the Framework must not allow this method to be concurrently called for the specified bundle.

Parameters:
bundle - The bundle requesting the service.
registration - The ServiceRegistration object for the requested service.
Returns:
A service object that must be an instance of all the classes named when the service was registered.
See Also:
BundleContext.getService(ServiceReference)

ungetService

void ungetService(Bundle bundle,
                  ServiceRegistration<S> registration,
                  S service)
Releases a service object.

The Framework invokes this method when a service has been released by a bundle. The service object may then be destroyed.

If this method throws an exception, a framework event of type FrameworkEvent.ERROR is fired containing a service exception of type ServiceException.FACTORY_EXCEPTION with the thrown exception as the cause.

Parameters:
bundle - The bundle releasing the service.
registration - The ServiceRegistration object for the service being released.
service - The service object returned by a previous call to the getService method.
See Also:
BundleContext.ungetService(ServiceReference)

Knopflerfish OSGi 5.2.0