/*
* Copyright (c) OSGi Alliance (2000, 2013). 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.annotation.versioning.ConsumerType;
import org.osgi.framework.ServiceReference;
The ServiceTrackerCustomizer interface allows a ServiceTracker to customize the service objects that are tracked. A ServiceTrackerCustomizer is called when a service is being added to a ServiceTracker. The ServiceTrackerCustomizer can then return an object for the tracked service. A ServiceTrackerCustomizer is also called when a tracked service is modified or has been removed from a ServiceTracker. The methods in this interface may be called as the result of a ServiceEvent being received by a ServiceTracker. Since ServiceEvents are synchronously delivered by the Framework, it is highly recommended that implementations of these methods do not register ( BundleContext.registerService), modify ( ServiceRegistration.setProperties) or unregister ( ServiceRegistration.unregister) a service while being synchronized on any object.
The ServiceTracker class is thread-safe. It does not call a ServiceTrackerCustomizer while holding any locks. ServiceTrackerCustomizer implementations must also be thread-safe.
Author: $Id: 0c3333455f7d80a7793c77ac9671baa4a02a89b9 $ Type parameters: @ThreadSafe
/**
* 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}.
*
* <p>
* 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.
*
* <p>
* 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 <S> The type of the service being tracked.
* @param <T> The type of the tracked object.
* @ThreadSafe
* @author $Id: 0c3333455f7d80a7793c77ac9671baa4a02a89b9 $
*/
@ConsumerType
public interface ServiceTrackerCustomizer<S, T> {
A service is being added to the ServiceTracker. This method is called before a service which matched the search parameters of the ServiceTracker is added to the ServiceTracker. This method should return the service object to be tracked for the specified ServiceReference. The returned service object is stored in the ServiceTracker and is available from the getService and getServices methods.
Params: - reference – The reference to the service being added to the
ServiceTracker.
Returns: The service object to be tracked for the specified referenced service or null if the specified referenced service should not be tracked.
/**
* A service is being added to the {@code ServiceTracker}.
*
* <p>
* 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<S> reference);
A service tracked by the ServiceTracker has been modified. This method is called when a service being tracked by the ServiceTracker has had it properties modified.
Params: - reference – The reference to the service that has been modified.
- service – The service object for the specified referenced service.
/**
* A service tracked by the {@code ServiceTracker} has been modified.
*
* <p>
* 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<S> reference, T service);
A service tracked by the ServiceTracker has been removed. This method is called after a service is no longer being tracked by the ServiceTracker.
Params: - reference – The reference to the service that has been removed.
- service – The service object for the specified referenced service.
/**
* A service tracked by the {@code ServiceTracker} has been removed.
*
* <p>
* 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<S> reference, T service);
}