/*
 * Copyright (c) OSGi Alliance (2008, 2009). 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.hooks.service;

import java.util.Collection;

import org.osgi.framework.ServiceEvent;

/**
 * OSGi Framework Service Event Hook Service.
 * 
 * <p>
 * Bundles registering this service will be called during framework service
 * (register, modify, and unregister service) operations.
 * 
 * @ThreadSafe
 * @version $Revision: 6860 $
 */

public interface EventHook {
	/**
	 * Event hook method. This method is called prior to service event delivery
	 * when a publishing bundle registers, modifies or unregisters a service.
	 * This method can filter the bundles which receive the event.
	 * 
	 * @param event The service event to be delivered.
	 * @param contexts A <code>Collection</code> of Bundle Contexts for bundles
	 *        which have listeners to which the specified event will be
	 *        delivered. The implementation of this method may remove bundle
	 *        contexts from the collection to prevent the event from being
	 *        delivered to the associated bundles. The collection supports all
	 *        the optional <code>Collection</code> operations except
	 *        <code>add</code> and <code>addAll</code>. Attempting to add to the
	 *        collection will result in an
	 *        <code>UnsupportedOperationException</code>. The collection is not
	 *        synchronized.
	 */
	void event(ServiceEvent event,
			Collection/* <? extends BundleContext> */contexts);
}
