/*
* Copyright (c) 2004-2007 Sun Microsystems, Inc. All rights reserved.
*
* The Sun Project JXTA(TM) Software License
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The end-user documentation included with the redistribution, if any, must
* include the following acknowledgment: "This product includes software
* developed by Sun Microsystems, Inc. for JXTA(TM) technology."
* Alternately, this acknowledgment may appear in the software itself, if
* and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
* not be used to endorse or promote products derived from this software
* without prior written permission. For written permission, please contact
* Project JXTA at http://www.jxta.org.
*
* 5. Products derived from this software may not be called "JXTA", nor may
* "JXTA" appear in their name, without prior written permission of Sun.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SUN
* MICROSYSTEMS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* JXTA is a registered trademark of Sun Microsystems, Inc. in the United
* States and other countries.
*
* Please see the license information page at :
* <http://www.jxta.org/project/www/license.html> for instructions on use of
* the license in source files.
*
* ====================================================================
*
* This software consists of voluntary contributions made by many individuals
* on behalf of Project JXTA. For more information on Project JXTA, please see
* http://www.jxta.org.
*
* This license is based on the BSD license adopted by the Apache Foundation.
*/
package net.jxta.util;
import net.jxta.logging.Logging;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* This a tool to implement selectable objects. It may be composed or extended.
* <p/>
* {@code SimpleSelectable} objects that are not {@code SimpleSelector} objects
* only report changes to their listeners.
* <p/>
* The listeners of a {@code SimpleSelectable} may be {@code SimpleSelector}
* objects or other {@code SimpleSelectable} objects. However the method to
* register non-selectors is and must remain protected since it would allow the
* connection of arbitrary listeners.
*
* @see SimpleSelector
*/
public abstract class AbstractSimpleSelectable implements SimpleSelectable {
/**
* Logger
*/
private final static transient Logger LOG = Logger.getLogger(AbstractSimpleSelectable.class.getName());
/**
* The identity reference for this selectable.
*
* @see SimpleSelectable.IdentityReference
*/
public final IdentityReference identityReference = new IdentityReference(this);
/**
* The object that is to reported to listeners as having changed. When this
* class is composed rather than extended, "this" is probably not the right
* choice.
*/
private final SimpleSelectable srcObject;
/**
* Registered Change Listeners.
* <p/>
* We use a weakHashMap as a Set. The values are never used.
*/
private final Map<SimpleSelectable, Object> myListeners = new WeakHashMap<SimpleSelectable, Object>(2);
/**
* Standard constructor for cases where the selectable object is this
* object.
*/
public AbstractSimpleSelectable() {
this.srcObject = this;
}
/**
* Standard constructor for cases where the selectable object is some other
* object.
*
* @param srcObject the source object
*/
public AbstractSimpleSelectable(SimpleSelectable srcObject) {
this.srcObject = srcObject;
}
/**
* {@inheritDoc}
*/
public IdentityReference getIdentityReference() {
return identityReference;
}
/**
* Tells whether there are registered selectors right now, or not. A
* SimpleSelectable that also registers with something else may want to
* unregister (with the obvious consistency precautions) if it no longer has
* selectors of its own.
*
* @return true if there are listeners.
*/
protected boolean haveListeners() {
synchronized(myListeners) {
return !myListeners.isEmpty();
}
}
/**
* This method takes any listener, not just a SimpleSelector.
*
* @param selectable The SimpleSelectable to register
*/
protected void registerListener(SimpleSelectable selectable) {
synchronized(myListeners) {
myListeners.put(selectable, null);
}
}
/**
* This method takes any listener, not just a SimpleSelector.
*
* @param selectable The SimpleSelectable to unregister
*/
protected void unregisterListener(SimpleSelectable selectable) {
synchronized(myListeners) {
myListeners.remove(selectable);
}
}
/**
* {@inheritDoc}
*/
public void register(SimpleSelector simpleSelector) {
registerListener(simpleSelector);
simpleSelector.itemChanged(this);
}
/**
* {@inheritDoc}
*/
public void unregister(SimpleSelector simpleSelector) {
unregisterListener(simpleSelector);
}
/**
* This method tells us that something changed and so we need to notify our
* selectors by invoking their {@code itemChanged()} method. This is
* normally invoked internally by the implementation. One of the reasons for
* the implementation to invoke this method is that a SimpleSelectable
* object that this one is registered with has changed and so has invoked
* the itemChanged method. However, the correlation between the two is left
* up to the implementation.
* <p/>
* No external synchronization needed, nor desirable.
*
* @return false if there are no selectors left (that's a suggestion for the
* implementation to use haveListeners and possibly unregister itself).
*/
protected final boolean notifyChange() {
Collection<SimpleSelectable> listeners;
synchronized(myListeners) {
listeners = new ArrayList<SimpleSelectable>(myListeners.keySet());
}
for (SimpleSelectable listener : listeners) {
try {
listener.itemChanged(srcObject);
} catch(Throwable all) {
if (Logging.SHOW_SEVERE && LOG.isLoggable(Level.SEVERE)) {
LOG.log(Level.SEVERE, "Uncaught Throwable in listener " + listener, all);
}
}
}
return !listeners.isEmpty();
}
}