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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.

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/*
 * Copyright (c) OSGi Alliance (2007, 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.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}.
 * 
 * 
 * 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.
 * 
 * 

 * 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  The type of the tracked object.
 * @ThreadSafe
 * @author $Id: 031b2979522768150d23ee70dfe62528432c19f7 $
 * @since 1.4
 */
@ConsumerType
public interface BundleTrackerCustomizer {
	/**
	 * A bundle is being added to the {@code BundleTracker}.
	 * 
	 * 

	 * 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.
	 * 
	 * 

	 * 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.
	 * 
	 * 
	 * 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);
}