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/*
* $Header: /cvshome/build/org.osgi.framework/src/org/osgi/framework/ServiceFactory.java,v 1.10 2007/02/20 00:16:30 hargrave Exp $
*
* Copyright (c) OSGi Alliance (2000, 2007). 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;
/**
* Allows services to provide customized service objects in the OSGi
* environment.
*
* <p>
* When registering a service, a <code>ServiceFactory</code> 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.
*
* <p>
* When this happens, the
* <code>BundleContext.getService(ServiceReference)</code> method calls the
* <code>ServiceFactory.getService</code> method to create a service object
* specifically for the requesting bundle. The service object returned by the
* <code>ServiceFactory</code> is cached by the Framework until the bundle
* releases its use of the service.
*
* <p>
* When the bundle's use count for the service equals zero (including the bundle
* stopping or the service being unregistered), the
* <code>ServiceFactory.ungetService</code> method is called.
*
* <p>
* <code>ServiceFactory</code> 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</code>.
*
* @see BundleContext#getService
* @ThreadSafe
* @version $Revision: 1.10 $
*/
public interface ServiceFactory {
/**
* Creates a new service object.
*
* <p>
* The Framework invokes this method the first time the specified
* <code>bundle</code> requests a service object using the
* <code>BundleContext.getService(ServiceReference)</code> method. The
* service factory can then return a specific service object for each
* bundle.
*
* <p>
* The Framework caches the value returned (unless it is <code>null</code>),
* and will return the same service object on any future call to
* <code>BundleContext.getService</code> from the same bundle.
*
* <p>
* The Framework will check if the returned service object is an instance of
* all the classes named when the service was registered. If not, then
* <code>null</code> is returned to the bundle.
*
* @param bundle The bundle using the service.
* @param registration The <code>ServiceRegistration</code> object for the
* 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
*/
public Object getService(Bundle bundle, ServiceRegistration registration);
/**
* Releases a service object.
*
* <p>
* The Framework invokes this method when a service has been released by a
* bundle. The service object may then be destroyed.
*
* @param bundle The bundle releasing the service.
* @param registration The <code>ServiceRegistration</code> object for the
* service.
* @param service The service object returned by a previous call to the
* <code>ServiceFactory.getService</code> method.
* @see BundleContext#ungetService
*/
public void ungetService(Bundle bundle, ServiceRegistration registration,
Object service);
}
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