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/*
* Copyright (c) 2003, 2004, 2005, 2006 Israfil Consulting Services Corporation
* Copyright (c) 2003, 2004, 2005, 2006 Christian Edward Gruber
* All Rights Reserved
*
* This software is licensed under the Berkeley Standard Distribution license,
* (BSD license), as defined below:
*
* 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. Neither the name of Israfil Consulting Services nor the names of its contributors
* may be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS 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 THE COPYRIGHT OWNER OR 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.
*
* $Id: NotificationCentre.java 125 2006-11-09 15:51:38Z cgruber $
*/
package net.israfil.foundation.notification;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.StringTokenizer;
import net.israfil.foundation.dynamic.DynamicUtil;
/**
* A nextstep-like central notification system.
* @author cgruber
*/
public class NotificationCentre {
private static NotificationCentre _shared = new NotificationCentre();
private Set<ObservationSpec> observers = new HashSet<ObservationSpec>();
protected NotificationCentre() {
}
public static NotificationCentre defaultCentre() {
return _shared;
}
/**
* This registers an object as an observer of notifications. The object
* registers interest in either a particular named notification, or a
* particular object who may issue the notifications, or the union of the
* two. The following table lists the possible combinations:
* <table>
* <tr>
* <th>Notification Name</th>
* <th>Sender Object</th>
* <th>Effect</th>
* </tr>
* <tr>
* <td>null</td>
* <td>a sender</td>
* <th>Notifications (of any name) from this sender are observed</th>
* </tr>
* <tr>
* <td>notification string</td>
* <td>null</td>
* <th>Notifications with this name (from any sender) are observed.</th>
* </tr>
* <tr>
* <td>notification string</td>
* <td>a sender</td>
* <th>Only notifications with this name and originating from this sender are observed</th>
* </tr>
* <tr>
* <td>null</td>
* <td>null</td>
* <th>All Notifications from any source will be sent (big performance drag)</th>
* </tr>
* </table>
* @param observer The object instance that wants to be registered
* @param callbackSignature Must be a method that takes a single Object parameter which will be a Notification at run-time, or a single Notification parameter
* @param notification The name of the notification to watch for (if any)
* @param sender The name of the object to whose notifications should be paid attention. (if any)
*/
public void addObserver(Object observer,
String callbackSignature,
String notification,
Object sender){
if (observer == null) return;
if (callbackSignature == null)
throw new IllegalArgumentException("Reciever did not pass in a callback method.");
if (!checkSignature(observer,callbackSignature))
throw new IllegalArgumentException("Reciever does not implement specified callback method.");
observers.add(new ObservationSpec(sender,notification, callbackSignature, observer));
}
/** Post a notification with the given nam and notifier. */
public void postNotification(Notification notification) {
for (ObservationSpec obs : this.observers) {
obs.postNotification(notification);
}
}
/** Post a notification with the given name, notifier, and with additional
* context information presented in a java.util.Map. */
public void postNotification(Object sender,String notification) {
postNotification(new Notification(sender,notification));
}
/** Post a notification with the given name, notifier, and with additional
* context information presented in a java.util.Map. */
public void postNotification(Object sender,String notification, Map<String,Object> info) {
postNotification(new Notification(sender,notification,info));
}
/** Removes an observer from any notofications with either or both a
* provided notification string, or notifier
*/
public void removeObserver(Object observer, String notification, Object sender) {
for (ObservationSpec obs : observers) {
if (obs.observer == observer &&
obs.sender == sender &&
(obs.notification == null || obs.notification.equals(notification))){
observers.remove(obs);
}
}
}
public void clearObservers() {
observers.clear();
}
private boolean checkSignature(Object receiver,String selector) {
if (!DynamicUtil.respondsTo(receiver,selector)) return false;
StringTokenizer st = new StringTokenizer(selector,":");
if (st.countTokens() != 2) return false;
st.nextToken();
String parameter = st.nextToken();
if (Notification.class.getName().equals(parameter)) return true;
if (Object.class.getName().equals(parameter)) return true;
return false;
}
/**
* TODO Use WeakReferences
*/
public class ObservationSpec {
public final Object sender;
public final String notification;
public final String callback;
public final Object observer;
private final int _hashCode;
public ObservationSpec(Object sender,String notification,String callback, Object observer) {
if (observer == null)
throw new IllegalArgumentException("Both sender and notification cannot be null");
this.sender = sender;
this.notification = notification;
this.callback = callback;
this.observer = observer;
// Pre-calculate hash
int code = 13;
if (sender != null) code *= sender.hashCode();
if (notification != null) code *= notification.hashCode();
code *= observer.hashCode();
this._hashCode = code;
}
public void postNotification(Notification notification) {
if (this.sender == null && this.notification == null) {
_post(notification);
} else if (this.sender == null) {
if (notification.notification.equals(this.notification))
_post(notification);
} else if (this.notification == null) {
if (notification.sender.equals(this.sender))
_post(notification);
} else {
if (notification.notification.equals(this.notification) && notification.sender.equals(this.sender))
_post(notification);
}
}
private void _post(Notification notification) {
DynamicUtil.performOn(this.observer,callback,new Object[]{notification} );
}
@Override
public int hashCode() {
return _hashCode;
}
}
}
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