org.osgi.util.tracker.ServiceTrackerCustomizer Maven / Gradle / Ivy
/*
* Copyright (c) OSGi Alliance (2000, 2010). 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.util.tracker;
import org.osgi.framework.ServiceReference;
/**
* The {@code ServiceTrackerCustomizer} interface allows a
* {@code ServiceTracker} to customize the service objects that are
* tracked. A {@code ServiceTrackerCustomizer} is called when a service is
* being added to a {@code ServiceTracker}. The
* {@code ServiceTrackerCustomizer} can then return an object for the
* tracked service. A {@code ServiceTrackerCustomizer} is also called when
* a tracked service is modified or has been removed from a
* {@code ServiceTracker}.
*
*
* The methods in this interface may be called as the result of a
* {@code ServiceEvent} being received by a {@code ServiceTracker}.
* Since {@code ServiceEvent}s are synchronously delivered by the
* Framework, it is highly recommended that implementations of these methods do
* not register ({@code BundleContext.registerService}), modify (
* {@code ServiceRegistration.setProperties}) or unregister (
* {@code ServiceRegistration.unregister}) a service while being
* synchronized on any object.
*
*
* The {@code ServiceTracker} class is thread-safe. It does not call a
* {@code ServiceTrackerCustomizer} while holding any locks.
* {@code ServiceTrackerCustomizer} implementations must also be
* thread-safe.
*
* @param The type of the service being tracked.
* @param The type of the tracked object.
* @ThreadSafe
* @version $Id: c654a963336cee74762b8f54c8cef8d5774f8b4d $
*/
public interface ServiceTrackerCustomizer {
/**
* A service is being added to the {@code ServiceTracker}.
*
*
* This method is called before a service which matched the search
* parameters of the {@code ServiceTracker} is added to the
* {@code ServiceTracker}. This method should return the service object
* to be tracked for the specified {@code ServiceReference}. The
* returned service object is stored in the {@code ServiceTracker} and
* is available from the {@code getService} and
* {@code getServices} methods.
*
* @param reference The reference to the service being added to the
* {@code ServiceTracker}.
* @return The service object to be tracked for the specified referenced
* service or {@code null} if the specified referenced service
* should not be tracked.
*/
public T addingService(ServiceReference reference);
/**
* A service tracked by the {@code ServiceTracker} has been modified.
*
*
* This method is called when a service being tracked by the
* {@code ServiceTracker} has had it properties modified.
*
* @param reference The reference to the service that has been modified.
* @param service The service object for the specified referenced service.
*/
public void modifiedService(ServiceReference reference, T service);
/**
* A service tracked by the {@code ServiceTracker} has been removed.
*
*
* This method is called after a service is no longer being tracked by the
* {@code ServiceTracker}.
*
* @param reference The reference to the service that has been removed.
* @param service The service object for the specified referenced service.
*/
public void removedService(ServiceReference reference, T service);
}