Click here to Skip to main content
Click here to Skip to main content
Add your own
alternative version

A remote dynamic Command pattern with GWT and LinkSet

, 19 Jan 2011
Command pattern is a very useful solution, but it causes some problems when used in a distributed environment.
// -----------------------------------------------------------------------------
//    LinkSet
//    Copyright: 2010 Lukasz Bownik (lukasz.bownik@gmail.com)
//
//    This file is part of LinkSet.
//
//    LinkSet is free software; you can redistribute it and/or modify
//    it under the terms of the Lesser GNU General Public License as published by
//    the Free Software Foundation; either version 2 of the License, or
//    (at your option) any later version.
//
//    LinkSet 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
//    Lesser GNU General Public License for more details.
//
//    You should have received a copy of the Lesser GNU General Public License
//    along with LinkSet; if not, write to the Free Software
//    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
// -----------------------------------------------------------------------------
package org.linkset;

import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;

/*******************************************************************************
 * A multithreaded event bus with exact matching
 * 
 * @author Lukasz Bownik (lukasz.bownik@gmail.com)
 ******************************************************************************/
public final class MultiThreadedEventBus implements EventBus {

	/***************************************************************************
	 * Constructor
	 **************************************************************************/
	public MultiThreadedEventBus() {

		this.thread = new Thread() {
			@Override
			public void run() {
				runInBackgrount();
			}
		};
		this.thread.start();
	}

	/***************************************************************************
	 * @see EventBus#addHandler(Class, Object, String)
	 **************************************************************************/
	public void add(final Class<?> eventType, final Object target,
			final String methodId) {

		final DefaultListenerManager manager = ensureManagerOf(eventType);
		manager.add(target, methodId);
	}

	/***************************************************************************
	 * @see EventBus#removeHandler(Class, Object, String)
	 **************************************************************************/
	public void remove(final Class<?> eventType, final Object target,
			final String methodId) {

		final DefaultListenerManager manager = ensureManagerOf(eventType);
		manager.remove(target, methodId);
	}

	/***************************************************************************
	 * @see EventBus#removeAllHandlers(Object)
	 **************************************************************************/
	public void removeAll(final Object target) {

		for (final DefaultListenerManager manager : this.map.values()) {
			manager.removeAll(target);
		}
	}

	/***************************************************************************
	 * @see EventBus#fire(Object)
	 **************************************************************************/
	public void fire(final Object event) throws InvocationTargetException,
			ExceptionInInitializerError {

		this.eventQueue.add(event);
	}

	/***************************************************************************
	 * @return true if a set is empty
	 **************************************************************************/
	public boolean isEmpty() {

		if (!this.map.isEmpty()) {
			for (final DefaultListenerManager manager : this.map.values()) {
				if (!manager.isEmpty()) {
					return false;
				}
			}
		}
		return true;
	}

	/***************************************************************************
	 * @return the amount of listeners in this set
	 **************************************************************************/
	public int size() {

		int size = 0;
		for (final DefaultListenerManager manager : this.map.values()) {
			size += manager.size();
		}
		return size;
	}

	/***************************************************************************
	 * Clears the set
	 **************************************************************************/
	public void clear() {

		this.map.clear();
	}

	/***************************************************************************
	 * Getr a listener manager of a givent event type
	 * 
	 * @param eventType
	 *            type of event
	 * @return listener manager
	 ***************************************************************************/
	private DefaultListenerManager ensureManagerOf(final Class<?> eventType) {

		DefaultListenerManager manager = this.map.get(eventType);
		if (manager == null) {
			manager = new DefaultListenerManager(eventType);
			this.map.put(eventType, manager);
		}
		return manager;
	}

	/***************************************************************************
	 * Fires events in backgraound
	 ***************************************************************************/
	private void runInBackgrount() {

		while (true) {
			try {
				final Object event = this.eventQueue.poll();
				if (event != null) {
					final DefaultListenerManager manager = this.map.get(event
							.getClass());
					if (manager != null) {
						manager.invokeAll(event);
					}
				} else {
					Thread.yield();
				}
			} catch (final Exception e) {
				e.printStackTrace();
			}
		}
	}

	/***************************************************************************
    *
    ***************************************************************************/
	private final Map<Class<?>, DefaultListenerManager> map = new HashMap<Class<?>, DefaultListenerManager>();
	private final Queue<Object> eventQueue = new ArrayBlockingQueue<Object>(50);
	private final Thread thread;
}

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article, along with any associated source code and files, is licensed under The GNU Lesser General Public License (LGPLv3)

Share

About the Author

No Biography provided

| Advertise | Privacy | Mobile
Web01 | 2.8.140821.2 | Last Updated 19 Jan 2011
Article Copyright 2011 by Łukasz Bownik
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid