org/objectweb/proactive/core/event/AbstractEventProducer.java

/* 
 * ################################################################
 * 
 * ProActive: The Java(TM) library for Parallel, Distributed, 
 *            Concurrent computing with Security and Mobility
 * 
 * Copyright (C) 1997-2007 INRIA/University of Nice-Sophia Antipolis
 * Contact: proactive@objectweb.org
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or any later version.
 *  
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 * USA
 *  
 *  Initial developer(s):               The ProActive Team
 *                        http://www.inria.fr/oasis/ProActive/contacts.html
 *  Contributor(s): 
 * 
 * ################################################################
 */ 
package org.objectweb.proactive.core.event;

import org.apache.log4j.Logger;
import org.objectweb.proactive.core.util.log.Loggers;
import org.objectweb.proactive.core.util.log.ProActiveLogger;


public abstract class AbstractEventProducer implements java.io.Serializable {
    //
    // -- PROTECTED MEMBERS -----------------------------------------------
    //
    protected static Logger logger = ProActiveLogger.getLogger(Loggers.EVENTS);

    protected boolean shouldSerializeListeners;

    protected transient ListenerList eventListeners;

    //
    // -- CONSTRUCTORS -----------------------------------------------
    //

    public AbstractEventProducer() {
        this(false);
    }

    public AbstractEventProducer(boolean shouldSerializeListeners) {
        this.shouldSerializeListeners = shouldSerializeListeners;
        if (shouldSerializeListeners) {
            eventListeners = new PlainListenerList();
        } else {
            eventListeners = new WeakReferenceListenerList();
        }
    }

    public AbstractEventProducer(boolean shouldSerializeListeners,
        boolean useWeakRef) {
        this.shouldSerializeListeners = shouldSerializeListeners;
        if (!shouldSerializeListeners && useWeakRef) {
            eventListeners = new WeakReferenceListenerList();
        } else {
            eventListeners = new PlainListenerList();
        }
    }

    //
    // -- PUBLIC METHODS -----------------------------------------------
    //
    //
    // -- PROTECTED METHODS -----------------------------------------------
    //

    protected boolean hasListeners() {
        return !eventListeners.isEmpty();
    }

    protected void addListener(ProActiveListener listener) {
        synchronized (eventListeners) {
            if (!eventListeners.contains(listener)) {
                eventListeners.add(listener);
            }
        }
    }

    protected void removeListener(ProActiveListener listener) {
        synchronized (eventListeners) {
            eventListeners.remove(listener);
        }
    }

    protected void notifyAllListeners(ProActiveEvent event) {
        synchronized (eventListeners) {
            java.util.Iterator iterator = eventListeners.iterator();
            while (iterator.hasNext()) {
                notifyOneListener((ProActiveListener) iterator.next(), event);
            }
        }
    }

    protected abstract void notifyOneListener(ProActiveListener listener,
        ProActiveEvent event);

    //
    // -- PRIVATE METHODS -----------------------------------------------
    //

    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException {
        s.writeBoolean(shouldSerializeListeners);
        if (shouldSerializeListeners) {
            s.writeObject(eventListeners);
        }
    }

    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
        shouldSerializeListeners = s.readBoolean();
        if (shouldSerializeListeners) {
            eventListeners = (ListenerList) s.readObject();
        } else {
            eventListeners = new WeakReferenceListenerList();
        }
    }

    //
    // -- INNER CLASSES -----------------------------------------------
    //

    protected interface ListenerList {

        public boolean isEmpty();

        public int size();

        public boolean contains(ProActiveListener listener);

        public boolean add(ProActiveListener listener);

        public boolean remove(ProActiveListener listener);

        public java.util.Iterator iterator();
    }

    private class PlainListenerList implements java.io.Serializable,
        ListenerList {
        protected java.util.ArrayList list;

        public PlainListenerList() {
            list = new java.util.ArrayList();
        }

        public boolean isEmpty() {
            return list.isEmpty();
        }

        public int size() {
            return list.size();
        }

        public boolean contains(ProActiveListener listener) {
            return list.contains(listener);
        }

        public boolean add(ProActiveListener listener) {
            return list.add(listener);
        }

        public boolean remove(ProActiveListener listener) {
            return list.remove(listener);
        }

        public java.util.Iterator iterator() {
            return list.iterator();
        }
    }

    private class WeakReferenceListenerList extends PlainListenerList {
        public WeakReferenceListenerList() {
        }

        public boolean contains(ProActiveListener listener) {
            java.util.Iterator iterator = iterator();
            while (iterator.hasNext()) {
                if (iterator.next() == listener) {
                    return true;
                }
            }
            return false;
        }

        public boolean add(ProActiveListener listener) {
            return list.add(new java.lang.ref.WeakReference(listener));
        }

        public boolean remove(ProActiveListener listener) {
            java.util.Iterator iterator = iterator();
            while (iterator.hasNext()) {
                if (iterator.next() == listener) {
                    iterator.remove();
                    return true;
                }
            }
            return false;
        }

        public java.util.Iterator iterator() {
            return new WeakReferenceIterator(list.iterator());
        }
    }

    private class WeakReferenceIterator implements java.util.Iterator {
        private java.util.Iterator iterator;
        private Object nextObject;

        public WeakReferenceIterator(java.util.Iterator iterator) {
            this.iterator = iterator;
            nextObject = getNextObject();
        }

        public boolean hasNext() {
            return nextObject != null;
        }

        public Object next() {
            Object result = nextObject;
            nextObject = getNextObject();
            return result;
        }

        public void remove() {
            iterator.remove();
        }

        private Object getNextObject() {
            while (iterator.hasNext()) {
                java.lang.ref.WeakReference ref = (java.lang.ref.WeakReference) iterator.next();
                Object target = ref.get();
                if (target == null) {
                    // object has been removed
                    //logger.debug("!!!!!!!!!!!! REMOVED A GARBAGED LISTENER");
                    iterator.remove();
                } else {
                    return target;
                }
            }
            return null;
        }
    }

    // end inner class WeakReferenceIterator
}

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