/*
* org.openmicroscopy.shoola.env.event.EventBusImpl
*
*------------------------------------------------------------------------------
* Copyright (C) 2006 University of Dundee. All rights reserved.
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*------------------------------------------------------------------------------
*/
package org.openmicroscopy.shoola.env.event;
//Java imports
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
//Third-party libraries
//Application-internal dependencies
/**
* Implements the<code>EventBus</code> interface, it is the pumping heart
* of the event propagation system.
* It maintains a de-multiplex table to
* keep track of what events have to be dispatched to which subscribers
*
*
* @author Jean-Marie Burel
* <a href="mailto:j.burel@dundee.ac.uk">j.burel@dundee.ac.uk</a>
* @author <br>Andrea Falconi
* <a href="mailto:a.falconi@dundee.ac.uk">
* a.falconi@dundee.ac.uk</a>
* @version 2.2
* <small>
* (<b>Internal version:</b> $Revision$ $Date$)
* </small>
* @since OME2.2
*/
class EventBusImpl
implements EventBus
{
/** Identifies the <code>IDLE</code> state. */
private static final int IDLE = 0;
/** Identifies the <code>DISPATCHING</code> state. */
private static final int DISPATCHING = 1;
/** Sequence of events to be dispatched. */
private LinkedList<AgentEvent> eventQueue;
/**
* Keeps track of what events have to be dispatched to which subscribers.
* This is a map in which each key is an event class and the corresponding
* value is a linked lists containing all the subscribers for that event
* type.
*/
private Map<Class<?>, LinkedList<AgentEventListener>> deMultiplexTable;
/** Marks the current state. */
private int state;
/** Dispatches the next event. */
private void dispatch()
{
//Grab the oldest event on the queue.
AgentEvent e = eventQueue.removeLast();
Class<?> eventType = e.getClass();
LinkedList<AgentEventListener>
evNotifList = deMultiplexTable.get(eventType);
if (evNotifList != null) {
Iterator<AgentEventListener> i = evNotifList.iterator();
AgentEventListener listener;
while (i.hasNext()) {
listener = i.next();
if (!listener.equals(e.getSource())) listener.eventFired(e);
}
} //else nobody registered for this event type.
}
/**
* Tells whether a given class inherits from {@link AgentEvent}.
*
* @param eventClass The class to verify.
* @return <code>true</code> if {@link AgentEvent} is an ancestor of
* <code>eventClass</code>, <code>false</code> otherwise.
*/
private boolean verifyInheritance(Class<?> eventClass)
{
Class<?> agtEvent = AgentEvent.class;
boolean b = false;
//Percolate inheritance hierarchy.
while (eventClass != null) {
if (eventClass == agtEvent) {
b = true;
break;
}
eventClass = eventClass.getSuperclass();
}
return b;
}
/** Creates a new instance. */
EventBusImpl()
{
eventQueue = new LinkedList<AgentEvent>();
deMultiplexTable =
new HashMap<Class<?>, LinkedList<AgentEventListener>>();
state = IDLE;
}
/**
* Implemented as specified by {@link EventBus}.
* @see EventBus#register(AgentEventListener, Class[])
*/
public void register(AgentEventListener subscriber, Class<?>[] eventTypes)
{
if (eventTypes == null)
throw new NullPointerException("No event types.");
for (int i = 0; i < eventTypes.length; ++i)
register(subscriber, eventTypes[i]);
}
/**
* Implemented as specified by {@link EventBus}.
* @see EventBus#register(AgentEventListener, Class)
*/
public void register(AgentEventListener subscriber, Class<?> eventType)
{
if (subscriber == null)
throw new NullPointerException("No subscriber.");
if (eventType == null)
throw new NullPointerException("No event type.");
if (verifyInheritance(eventType)) {
LinkedList<AgentEventListener> evNotifList =
deMultiplexTable.get(eventType);
if (evNotifList == null) {
evNotifList = new LinkedList<AgentEventListener>();
deMultiplexTable.put(eventType, evNotifList);
}
if (!evNotifList.contains(subscriber))
evNotifList.add(subscriber);
}
}
/**
* Implemented as specified by {@link EventBus}.
* @see EventBus#remove(AgentEventListener, Class)
*/
public void remove(AgentEventListener subscriber, Class<?> eventType)
{
if (subscriber == null)
throw new NullPointerException("No subscriber.");
if (eventType == null)
throw new NullPointerException("No event type.");
LinkedList<AgentEventListener>
evNotifList = deMultiplexTable.get(eventType);
if (evNotifList != null) {
evNotifList.remove(subscriber);
if (evNotifList.isEmpty()) deMultiplexTable.remove(eventType);
}
}
/**
* Implemented as specified by {@link EventBus}.
* @see EventBus#remove(AgentEventListener, Class[])
*/
public void remove(AgentEventListener subscriber, Class<?>[] eventTypes)
{
if (eventTypes == null)
throw new NullPointerException("No event types.");
for (int i = 0; i < eventTypes.length; ++i)
remove(subscriber, eventTypes[i]);
}
/**
* Implemented as specified by {@link EventBus}.
* @see EventBus#remove(AgentEventListener)
*/
public void remove(AgentEventListener subscriber)
{
Iterator<Class<?>> e = deMultiplexTable.keySet().iterator();
while (e.hasNext())
remove(subscriber, e.next());
}
/**
* Implemented as specified by {@link EventBus}.
* @see EventBus#hasListenerFor(Class)
*/
public boolean hasListenerFor(Class<?> eventType)
{
return (deMultiplexTable.get(eventType) != null);
}
/**
* Implemented as specified by {@link EventBus}.
* @see EventBus#post(AgentEvent)
*/
public void post(AgentEvent e)
{
if (e == null) throw new NullPointerException("No event.");
switch (state) {
case IDLE:
state = DISPATCHING;
eventQueue.addFirst(e);
while (!eventQueue.isEmpty()) dispatch();
state = IDLE;
break;
case DISPATCHING:
eventQueue.addFirst(e);
}
}
}