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/*
* Copyright (c) OSGi Alliance (2000, 2014). All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.osgi.framework;
import org.osgi.annotation.versioning.ConsumerType;
/**
* A factory for {@link Constants#SCOPE_BUNDLE bundle scope} services. The
* factory can provide service objects customized for each bundle in the OSGi
* environment.
*
* <p>
* When registering a service, a {@code ServiceFactory} object can be used
* instead of a service object, so that the bundle developer can create a
* customized service object for each bundle that is using the service.
*
* <p>
* When a bundle {@link BundleContext#getService(ServiceReference) requests} the
* service object, the framework calls the
* {@link #getService(Bundle, ServiceRegistration) getService} method to return
* a service object customized for the requesting bundle. The returned service
* object is cached by the Framework for subsequent calls to
* {@link BundleContext#getService(ServiceReference)} until the bundle releases
* its use of the service.
*
* <p>
* When the bundle's use count for the service is
* {@link BundleContext#ungetService(ServiceReference) decremented} to zero
* (including the bundle stopping or the service being unregistered), the
* framework will call the
* {@link #ungetService(Bundle, ServiceRegistration, Object) ungetService}
* method.
*
* <p>
* {@code 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 {@code ServiceFactory}.
*
* @param <S> Type of Service
* @see BundleContext#getService(ServiceReference)
* @ThreadSafe
* @author $Id$
*/
@ConsumerType
public interface ServiceFactory<S> {
/**
* Returns a service object for a bundle.
*
* <p>
* The Framework invokes this method the first time the specified
* {@code bundle} requests a service object using the
* {@link BundleContext#getService(ServiceReference)} method. The factory
* can then return a customized service object for each bundle.
*
* <p>
* The Framework must check that the returned service object is valid. If
* the returned service object is {@code null} or is not an
* {@code instanceof} all the classes named when the service was registered,
* a framework event of type {@link FrameworkEvent#ERROR} is fired
* containing a service exception of type
* {@link ServiceException#FACTORY_ERROR} and {@code null} is returned to
* the bundle. If this method throws an exception, a framework event of type
* {@link FrameworkEvent#ERROR} is fired containing a service exception of
* type {@link ServiceException#FACTORY_EXCEPTION} with the thrown exception
* as the cause and {@code null} is returned to the bundle. If this method
* is recursively called for the specified bundle, a framework event of type
* {@link FrameworkEvent#ERROR} is fired containing a service exception of
* type {@link ServiceException#FACTORY_RECURSION} and {@code null} is
* returned to the bundle.
*
* <p>
* The Framework caches the valid service object and will return the same
* service object on any future call to
* {@link BundleContext#getService(ServiceReference)} for the specified
* bundle. This means the Framework must not allow this method to be
* concurrently called for the specified bundle.
*
* @param bundle The bundle requesting the service.
* @param registration The {@code ServiceRegistration} object for the
* requested service.
* @return A service object that <strong>must</strong> be an instance of all
* the classes named when the service was registered.
* @see BundleContext#getService(ServiceReference)
*/
public S getService(Bundle bundle, ServiceRegistration<S> registration);
/**
* Releases a service object customized for a bundle.
*
* <p>
* The Framework invokes this method when a service has been released by a
* bundle. The service object may then be destroyed.
*
* <p>
* If this method throws an exception, a framework event of type
* {@link FrameworkEvent#ERROR} is fired containing a service exception of
* type {@link ServiceException#FACTORY_EXCEPTION} with the thrown exception
* as the cause.
*
* @param bundle The bundle releasing the service.
* @param registration The {@code ServiceRegistration} object for the
* service being released.
* @param service The service object returned by a previous call to the
* {@link #getService(Bundle, ServiceRegistration) getService}
* method.
* @see BundleContext#ungetService(ServiceReference)
*/
public void ungetService(Bundle bundle, ServiceRegistration<S> registration, S service);
}
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