Metacat

/**

 *  '$RCSfile$'

 *    Purpose: A Class that implements session utility methods 

 *  Copyright: 2008 Regents of the University of California and the

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Michael Daigle

 * 

 *   '$Author: daigle $'

 *     '$Date: 2009-08-26 14:20:43 -0700 (Wed, 26 Aug 2009) $'

 * '$Revision: 5041 $'

 *

 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

package edu.ucsb.nceas.metacat.service;

import java.io.PrintWriter;

import java.util.Calendar;

import java.util.Hashtable;

import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

import edu.ucsb.nceas.metacat.properties.PropertyService;

import edu.ucsb.nceas.metacat.shared.BaseService;

import edu.ucsb.nceas.metacat.shared.ServiceException;

import edu.ucsb.nceas.metacat.util.SessionData;

import edu.ucsb.nceas.utilities.PropertyNotFoundException;

public class SessionService extends BaseService {

	private static SessionService sessionService = null;

	private static int sessionTimeoutMinutes;

	private static Logger logMetacat = Logger.getLogger(SessionService.class);

	private static Hashtable<String, SessionData> sessionHash = null;

	private static final String PUBLIC_SESSION_ID = "0";

	/**

	 * private constructor since this is a singleton

	 */

	private SessionService() throws ServiceException {		

		_serviceName = "SessionService";

		String sessionTimeoutStr = null;

		try {

			sessionHash = new Hashtable<String, SessionData>();

			sessionTimeoutStr = PropertyService.getProperty("session.timeoutMinutes");

			sessionTimeoutMinutes = Integer.parseInt(sessionTimeoutStr);

			logMetacat.debug("SessionService() - Registering public session id: " + 

					PUBLIC_SESSION_ID);

			registerSession(PUBLIC_SESSION_ID, "public", null, null);

		} catch (PropertyNotFoundException pnfe) {

			throw new ServiceException("SessionService() - Error getting property: " + 

					pnfe.getMessage());

		} catch (NumberFormatException nfe) {

			throw new ServiceException("SessionService() - Error parsing session timeout minutes: " + 

					sessionTimeoutStr);

		}

	}

	/**

	 * Get the single instance of SessionService.

	 * 

	 * @return the single instance of SessionService

	 */

	public static SessionService getInstance() throws ServiceException {

		if (sessionService == null) {

			sessionService = new SessionService();

		}

		return sessionService;

	}

	public boolean refreshable() {

		return false;

	}

	public void doRefresh() throws ServiceException {

		return;

	}

	public void stop() throws ServiceException {

		return;

	}

	/**

	 * Register a session in the session hash table.  This uses

	 * the parameters passed in to create a SessionData object.

	 * 

	 * @param sessionId

	 *            the ID of the session to register

	 * @param userName

	 *            the user name of the session

	 * @param groupNames

	 *            the group names for the session

	 * @param password

	 *            the password for the session

	 */

	public static void registerSession(String sessionId, String userName,

			String[] groupNames, String password) throws ServiceException {

		if (sessionId == null) {

			throw new ServiceException("SessionService.registerSession - " + 

					"Cannot register a null session id");

		}

		logMetacat.debug("SessionService.registerSession - Registering session id: " + sessionId);

		SessionData sessionData = new SessionData(sessionId, userName, groupNames,

				password);

		sessionHash.put(sessionId, sessionData);

	}

	/**

	 * Register a session in the session hash table.

	 * 

	 * @param sessionData

	 *            the session data object to add to the session hash

	 */

	public static void registerSession(SessionData sessionData) throws ServiceException {

		if (sessionData == null) {

			throw new ServiceException("SessionService.registerSession - " + 

					"Cannot register null session data");

		}

		logMetacat.debug("SessionService.registerSession - Registering session " + 

				"data with id: " + sessionData.getId());

		sessionHash.put(sessionData.getId(), sessionData);

	}

	/**

	 * Unregister a session from the session hash table.

	 * 

	 * @param sessionId

	 *            the id of the session to remove.

	 */

	public static void unRegisterSession(String sessionId) {

		if (sessionId != null) {

			logMetacat.error("SessionService.unRegisterSession - trying to " + 

					"unregister a session with null id");

			sessionHash.remove(sessionId);

		}

	}

	/**

	 * Check if a session is registered in the session hash table. 

	 * 

	 * @param sessionId

	 *            the id of the session to look for.

	 */

	public static boolean isSessionRegistered(String sessionId) {		

		if (sessionId == null) {

			logMetacat.error("SessionService.isSessionRegistered - trying to check if a " + 

					"session with null id is registered");

			return false;

		}

		checkTimeout(sessionId);

		return sessionHash.containsKey(sessionId);

	}

	/**

	 * Check if a session is registered in the session hash table. Write results

	 * in XML format to output.

	 * 

	 * @param out

	 *            the output stream to write to.

	 * @param sessionId

	 *            the id of the session to look for.

	 */

	public static void validateSession(PrintWriter out, HttpServletResponse response, 

			String sessionId) {		

		response.setContentType("text/xml");

		out.println("<?xml version=\"1.0\"?>");

		out.write("<validateSession><status>");

		if (sessionId != null && isSessionRegistered(sessionId)) {

			out.write("valid");

		} else {

			out.write("invalid");

		}

		out.write("</status>");

		out.write("<sessionId>" + sessionId + "</sessionId></validateSession>");				

	}

	/**

	 * Get a registered session from the session hash table. 

	 * TODO MCD need to time sessions out

	 * 

	 * @param sessionId

	 *            the id of the session to retrieve.

	 */

	public static SessionData getRegisteredSession(String sessionId) {

		if (sessionId == null) {

			logMetacat.error("SessionService.getRegisteredSession - trying to get a session with null id");

			return null;

		}

		checkTimeout(sessionId);

		return sessionHash.get(sessionId);

	}

	/**

	 * Get the public session from the session hash table. 

	 */

	public static SessionData getPublicSession() {

		return sessionHash.get(PUBLIC_SESSION_ID);

	}

	/**

	 * Keep a session active by updating its last accessed time. 

	 * 

	 * @param sessionId

	 *            the id of the session to update.

	 */

	public static synchronized void touchSession(String sessionId) {

		if (sessionId == null) {

			logMetacat.error("SessionService.touchSession - trying to touch a session with null id");

		} else if (isSessionRegistered(sessionId)) {

			SessionData sessionData = getRegisteredSession(sessionId);

			sessionData.setLastAccessedTime();

		}

	}

	private static void checkTimeout (String sessionId) {

		SessionData sessionData = null;

		if ((sessionData = sessionHash.get(sessionId)) != null) {

			Calendar expireTime = Calendar.getInstance();

			Calendar lastAccessedTime = sessionData.getLastAccessedTime();

			expireTime.add(Calendar.MINUTE, 0 - sessionTimeoutMinutes);

			if(lastAccessedTime.compareTo(expireTime) < 0 ) {

				unRegisterSession(sessionId);

			}

		}

	}

}