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/*
* Copyright (c) OSGi Alliance (2007, 2012). 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.Bundle;
import org.osgi.framework.BundleEvent;
/**
* The {@code BundleTrackerCustomizer} interface allows a {@code BundleTracker}
* to customize the {@code Bundle}s that are tracked. A
* {@code BundleTrackerCustomizer} is called when a bundle is being added to a
* {@code BundleTracker}. The {@code BundleTrackerCustomizer} can then return an
* object for the tracked bundle. A {@code BundleTrackerCustomizer} is also
* called when a tracked bundle is modified or has been removed from a
* {@code BundleTracker}.
*
* <p>
* The methods in this interface may be called as the result of a
* {@code BundleEvent} being received by a {@code BundleTracker}. Since
* {@code BundleEvent}s are received synchronously by the {@code BundleTracker},
* it is highly recommended that implementations of these methods do not alter
* bundle states while being synchronized on any object.
*
* <p>
* The {@code BundleTracker} class is thread-safe. It does not call a
* {@code BundleTrackerCustomizer} while holding any locks.
* {@code BundleTrackerCustomizer} implementations must also be thread-safe.
*
* @param <T> The type of the tracked object.
* @ThreadSafe
* @version $Id: 727e757d2fa2940c88c9b74c8d299de6b3a7d0d0 $
* @since 1.4
*/
public interface BundleTrackerCustomizer<T> {
/**
* A bundle is being added to the {@code BundleTracker}.
*
* <p>
* This method is called before a bundle which matched the search parameters
* of the {@code BundleTracker} is added to the {@code BundleTracker}. This
* method should return the object to be tracked for the specified
* {@code Bundle}. The returned object is stored in the
* {@code BundleTracker} and is available from the
* {@link BundleTracker#getObject(Bundle) getObject} method.
*
* @param bundle The {@code Bundle} being added to the {@code BundleTracker}
* .
* @param event The bundle event which caused this customizer method to be
* called or {@code null} if there is no bundle event associated with
* the call to this method.
* @return The object to be tracked for the specified {@code Bundle} object
* or {@code null} if the specified {@code Bundle} object should not
* be tracked.
*/
public T addingBundle(Bundle bundle, BundleEvent event);
/**
* A bundle tracked by the {@code BundleTracker} has been modified.
*
* <p>
* This method is called when a bundle being tracked by the
* {@code BundleTracker} has had its state modified.
*
* @param bundle The {@code Bundle} whose state has been modified.
* @param event The bundle event which caused this customizer method to be
* called or {@code null} if there is no bundle event associated with
* the call to this method.
* @param object The tracked object for the specified bundle.
*/
public void modifiedBundle(Bundle bundle, BundleEvent event, T object);
/**
* A bundle tracked by the {@code BundleTracker} has been removed.
*
* <p>
* This method is called after a bundle is no longer being tracked by the
* {@code BundleTracker}.
*
* @param bundle The {@code Bundle} that has been removed.
* @param event The bundle event which caused this customizer method to be
* called or {@code null} if there is no bundle event associated with
* the call to this method.
* @param object The tracked object for the specified bundle.
*/
public void removedBundle(Bundle bundle, BundleEvent event, T object);
}
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