gethierarchytreeaction.java

老外的在线考试

/*
 * CyberTester - J2EE Web application for creating, delivering and managing tests/exams/surveys. 
 * Copyright (C) 2003 CyberDemia Research and Services Pty Ltd
 *
 * 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 (see the file COPYING); 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 program for complete text of license.
 */
package com.cyberdemia.cybertester.admin;

import javax.servlet.http.*;
import org.apache.struts.action.*;

import com.cyberdemia.cybertester.Constants;
import com.cyberdemia.cybertester.CyberTesterUtils;
import com.cyberdemia.cybertester.common.TreeNode;
import com.cyberdemia.school.*;
import com.cyberdemia.user.UserManager;
import com.cyberdemia.user.UserManagerHome;

import java.util.logging.*;
import java.util.*;

/**
 * GetHierarchyTreeAction is a Struts action to render a hierarchy tree.
 * 
 * @author Alexander Yap
 */
public final class GetHierarchyTreeAction extends AbstractAdminAction
{
	public static final String EXPAND_NODE_ACTION = "expand";
	public static final String COLLAPSE_NODE_ACTION = "collapse";
	public static final String SELECT_NODE_ACTION = "select";
	public static final String RESTORE_NODE_ACTION = "restore";

	protected ActionForward doPerform(
		ActionMapping mapping, ActionForm form,
		HttpServletRequest request, HttpServletResponse response,
		HttpSession session) throws Exception	
	{
		Logger logger = CyberTesterUtils.getLogger();
		
		String action = request.getParameter(Constants.ACTION_KEY);
		IHierarchy rootNode = SchoolConfig.getInstance().getHierarchyRoot();
		// The hierId parameter tells this action which node of the tree 
		// to "open", i.e. to request the children for.
		// If null, this may be a relogin so try to restore the previously
		// selected leaf-node (if any).
		String hierId = request.getParameter( "hierId");
		if (hierId==null)
		{
			UserManagerHome userMgrHome = CyberTesterUtils.getUserManagerHome();
			UserManager userMgr = (UserManager)userMgrHome.create();
			Integer userId = (Integer)session.getAttribute(Constants.USER_ID_KEY);
			String[] selectedHierId = userMgr.getResourcesInUser( userId , SELECTED_HIERARCHY_ID_RESOURCE_CATEGORY);
			// Expect at most one element, but if there is more, just ignore the redundant ones.
			if ((selectedHierId.length>0) && (selectedHierId[0].length()>0))
			{
				hierId = selectedHierId[0];
				action = RESTORE_NODE_ACTION;
				logger.fine("Restoring previously selected node at "+hierId);				
			}
		}
		// If there is no previously selected leaf-node, default hierId to 
		// refer to the root node. 
		if (hierId==null)
		{
			hierId = rootNode.getId().toString();
		}
		
		logger.fine("Resolving node "+hierId);
		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() );
		if (!rootNode.getId().equals(rootId))
		{
			throw new NumberFormatException("Hierarchy ID "+hierId+" is invalid, wrong root node ID.");
		}		

		LinkedList treeNodeList = new LinkedList();
		// Add the rootNode to the first position.
		treeNodeList.add(0, new TreeNode(rootNode, false, -1) );
		request.setAttribute(Constants.TREE_NODES_KEY, treeNodeList);
		
		if (COLLAPSE_NODE_ACTION.equalsIgnoreCase(action))
		{
			openToTreeNode(rootNode, 0, tokenizer, treeNodeList);
			session.removeAttribute(AdminConstants.SELECTED_HIERARCHY_ID_KEY);
		}
		else if (SELECT_NODE_ACTION.equalsIgnoreCase(action))
		{
			openToTreeNode(rootNode, 0, tokenizer, treeNodeList);
			session.setAttribute(AdminConstants.SELECTED_HIERARCHY_ID_KEY, hierId);
			// Remember selected node
			UserManagerHome userMgrHome = CyberTesterUtils.getUserManagerHome();
			UserManager userMgr = (UserManager)userMgrHome.create();
			Integer userId = (Integer)session.getAttribute(Constants.USER_ID_KEY);
			userMgr.setSingleResourceToUser(SELECTED_HIERARCHY_ID_RESOURCE_CATEGORY, hierId , userId);
		}
		else if (EXPAND_NODE_ACTION.equalsIgnoreCase(action))
		{
			// We need to build a list of nodes to render the tree.
			// The tree must be expanded only down the path to the hierNode.
			// hierNode itself must be expanded, as well as all its direct ancestors.
			// Expand its children, all the way down to the referenced node
			int attachPos = openToTreeNode(rootNode, 0, tokenizer, treeNodeList);
			addChildrenNodes( attachPos, treeNodeList );
			session.removeAttribute(AdminConstants.SELECTED_HIERARCHY_ID_KEY);
		}
		else if (RESTORE_NODE_ACTION.equalsIgnoreCase(action))
		{
			// Expand to node to restore, followed by a select
			int attachPos = openToTreeNode(rootNode, 0, tokenizer, treeNodeList);
			addChildrenNodes( attachPos, treeNodeList );
			session.setAttribute(AdminConstants.SELECTED_HIERARCHY_ID_KEY, hierId);
		}
			
		return mapping.findForward(Constants.SUCCESS);
	}
	
	private void addChildrenNodes( int parentPos, LinkedList treeNodeList )
	{
		TreeNode parentNode = (TreeNode)treeNodeList.get(parentPos);
		parentNode.setExpanded( true );
		IHierarchy[] children = parentNode.getHierarchyNode().getChildren();
		
		for (int c=0; c<children.length; c++)
		{
			IHierarchy child = children[c];
			treeNodeList.add(parentPos+c+1, new TreeNode(child, false, parentPos) );
		}

	}
	
	private int openToTreeNode( IHierarchy hierNode, int nodePos, StringTokenizer hierIdTokenizer, LinkedList treeNodeList)
	{
		// Get the next child to go down.
		int childIdInPath = -1;
		if (hierIdTokenizer.hasMoreTokens())
		{
			childIdInPath = Integer.parseInt(hierIdTokenizer.nextToken());			
		}
		if (childIdInPath<0)
		{
			return nodePos;
		}
		
		int childPosInPath = -1;
		IHierarchy childInPath =null;
		
		// Get its children, then insert them into positions following the hierNode.
		IHierarchy[] children = hierNode.getChildren();
		TreeNode parentNode = (TreeNode)treeNodeList.get(nodePos);
		parentNode.setExpanded( children.length > 0 );
		
		for (int c=0; c<children.length; c++)
		{
			IHierarchy child = children[c];
			if ((childIdInPath!=-1) && (child.getId().intValue()==childIdInPath))
			{
				childPosInPath=nodePos+c+1;
				childInPath = child;
			}
			treeNodeList.add(nodePos+c+1, 
				new TreeNode(child, false, nodePos)
			);
		}
		
		
		// Expand the next child in the path.
		int retPos = nodePos;
		if (childInPath!=null)
		{
			retPos = openToTreeNode(childInPath, childPosInPath, hierIdTokenizer, treeNodeList);
		}
		return retPos;
	}
	
	private static final String SELECTED_HIERARCHY_ID_RESOURCE_CATEGORY = "selectedHierId";
}