EventManager.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.cocoon.portal.event;

import org.apache.avalon.framework.component.Component;
import org.apache.cocoon.ProcessingException;

/**
 * This component manages the event handling mechanism in the portal.
 * The event mechanism is based on the publisher/subscriber principle.
 * An interested component (a {@link org.apache.cocoon.portal.event.Receiver}
 * can subscribe itself for a specific class (or classes) of events.
 * All Events have a common ancestor type {@link Event} and the event types are 
 * identified by a (sub)class
 * 
 * The old design which is now deprecated has been inspired by the paper by 
 * Gupta, S., J. M. Hartkopf, and S. Ramaswamy, in Java Report, Vol. 3, No. 7, July 1998, 19-36,
 * "Event Notifier: A Pattern for Event Notification".  
 * 
 * EventManager brokers events between a <tt>Publisher</tt>, which produces events,
 * and a <tt>Subscriber</tt>, which handles the notification of events.
 * A <tt>Filter</tt> discards events not of interest to a subscriber.
 * 
 * @author <a href="mailto:cziegeler@s-und-n.de">Carsten Ziegeler</a>
 * @author <a href="mailto:volker.schmitt@basf-it-services.com">Volker Schmitt</a>
 * @author Mauro Talevi
 * 
 * @version CVS $Id$
 */
public interface EventManager extends Component {
 
    /**
     * Represents the role of the service
     */
    String ROLE = EventManager.class.getName(); 
    
     /**
      *  Returns the Publisher with which events can be published.
      *  @deprecated Use {@link #send(Event)} instead.
      */
    Publisher getPublisher();
    
     /**
      *  Returns the Register with which subscribers can 
      *  subscribe and unsubscribe interest to given Events.
      *  @deprecated Use {@link #subscribe(Receiver)} and {@link #unsubscribe(Receiver)}.
      */
    Register getRegister();

    /**
     * Process the events
     */
    void processEvents()
    throws ProcessingException;

    /**
     * Publish an event. All registered receivers get notified.
     * @param event The event to broadcast.
     */
    void send(Event event);

    /**
     * Subscribes a receiver for a specific type of event.  
     */
    void subscribe(Receiver receiver);

    /**
     * Unsubscribes a receiver for all events.
     */
    void unsubscribe(Receiver receiver);

}