ActionManager.java

/*
 * ActionManager.java
 *
 * Version: $Revision: 3984 $
 *
 * Date: $Date: 2009-06-29 22:33:25 -0400 (Mon, 29 Jun 2009) $
 *
 * Copyright (c) 2002-2009, The DSpace Foundation.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - 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.
 *
 * - Neither the name of the DSpace Foundation 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
 * HOLDERS 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.
 */
package org.dspace.app.itemupdate;

import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * 	 Container for UpdateActions      
 *    Order of actions is very import for correct processing.  This implementation
 *     supports an iterator that returns the actions in the order in which they are
 *     put in.  Adding the same action a second time has no effect on this order.
 * 
 *
 */
public class ActionManager implements Iterable<UpdateAction> {
	
	private Map<Class<? extends UpdateAction>, UpdateAction> registry 
                     = new LinkedHashMap<Class<? extends UpdateAction>, UpdateAction>();
	
	public UpdateAction getUpdateAction(Class<? extends UpdateAction> actionClass) 
	throws InstantiationException, IllegalAccessException
	{
		UpdateAction action =  registry.get(actionClass);
		
		if (action == null)
		{
			action = actionClass.newInstance();
			registry.put(actionClass, action);
		}
		
		return action;		
	}
	
	/**
	 * 
	 * @return whether any actions have been registered with this manager
	 */
	public boolean hasActions()
	{
		return !registry.isEmpty();
	}
	
	/**
	 * 	 This implementation guarantees the iterator order is the same as the order
	 *   in which updateActions have been added
	 * 
	 * @return iterator for UpdateActions
	 */
	public Iterator<UpdateAction> iterator()
	{
		return new Iterator<UpdateAction>() 
		{ 			
			private Iterator<Class<? extends UpdateAction>> itr = registry.keySet().iterator();
			
			public boolean hasNext()
			{
				return itr.hasNext();
			}
			
			public UpdateAction next()
			{
				return registry.get(itr.next());
			}
			
			//not supported
			public void remove()
			{
				throw new UnsupportedOperationException();
			}
		};
		
	}
}