schoolutils.java

老外的在线考试

/*
 * SchoolEJB - CyberDemia's library of EJBs for educational related services.
 * Copyright (C) 2003 CyberDemia Research and Services
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 *
 * See the COPYING file located in the top-level-directory of
 * the archive of this library for complete text of license.
 */
package com.cyberdemia.school;

import java.util.*;
import javax.ejb.*;
import java.util.logging.*;

/**
* Utility class that provides some methods that are useful
* throughout the SchoolEJB module.
*
* @author Alexander Yap
*/
public abstract class SchoolUtils
{

	private static Logger s_logger = Logger.getLogger("com.cyberdemia.school");
	public static Logger getLogger()
	{
		return s_logger;
	}

	/**
	* Converts "hierarchy ID" to its equivalent IHierarchy node.
	* @param hierId Hierarchy ID as a String.
	* @return IHierarchy node that corresponds to hierId, or null if it can't be resolved to any node.
	*/
	public static IHierarchy getNodeFromHierarchyId(String hierId)
	{
		IHierarchy node = null;
		StringTokenizer tokenizer = new StringTokenizer(hierId, IHierarchy.HIERARCHY_ID_SEPARATOR);
		if (!tokenizer.hasMoreTokens())
			throw new NumberFormatException("Hierarchy ID "+hierId+" is invalid.");
		Integer rootId = new Integer( tokenizer.nextToken() );
		IHierarchy rootNode = SchoolConfig.getInstance().getHierarchyRoot();
		if (rootNode.getId().equals(rootId))
		{
			node = rootNode;
			while(tokenizer.hasMoreTokens())
			{
				IHierarchy childNode =  null;
				try
				{
					childNode = node.getChild(new Integer(tokenizer.nextToken()));
				}
				catch (NumberFormatException nfex)
				{
                    // Ignore, childNode remains null.
				}
				if (childNode!=null)
				{
					node = childNode;
				}
				else
				{	// Failed to resolve the hierarchy ID, set node to null and break;
					s_logger.warning("Failed to resolve Hierarchy ID "+hierId);
					node = null;
					break;
				}
			}
		}
		return node;
	}
	
	/**
	 * Gets a list of all nodes in the hierarchy path from the root node to
	 * the specified node.
	 * @param node Node at the end of the list.
	 * @return List of IHierarchy nodes.
	 */
	public static List getHierarchyNodeList(IHierarchy node)
	{
		LinkedList hierList = new LinkedList();
		IHierarchy chkNode = node;
		while (chkNode!=null)
		{
			hierList.addFirst(chkNode);
			chkNode = chkNode.getParent();
		}
		return hierList;
	}

	/**
	 * Converts any exception to an EJBException, unless it is already an EJBException.
	 * @param ex Source exception.
	 * @return An EJBException.
	 */
	public static EJBException convertToEJBException(Exception ex)
	{
		if (ex instanceof EJBException)
			return (EJBException)ex;
		return new EJBException(ex);	
	}
	
}