SessionCleanupServlet.java

package org.wahlzeit.servlets;

import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.Key;
import org.wahlzeit.model.Client;
import org.wahlzeit.model.Guest;
import org.wahlzeit.model.UserManager;
import org.wahlzeit.services.LogBuilder;
import org.wahlzeit.services.OfyService;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.util.List;
import java.util.logging.Logger;

/**
 * This servlet is run to cleanup expired sessions.
 */
public class SessionCleanupServlet extends HttpServlet {

	private static final String SESSION_ENTITY_TYPE = "_ah_SESSION";
	private static final String EXPIRES_PROP = "_expires";

	private static final Logger log = Logger.getLogger(SessionCleanupServlet.class.getName());

	@Override
	public void service(HttpServletRequest request, HttpServletResponse response) {
		if ("clear".equals(request.getQueryString())) {
			clearAll(response);
		}
	}

	/**
	 * Clears all {@link HttpSession}s in the datastore that are expired and if they are guest sessions, deletes the
	 * corresponding {@link Guest} object, too.
	 */
	private void clearAll(HttpServletResponse response) {

		List<Object> killList = OfyService.ofy().load().
				kind(SESSION_ENTITY_TYPE).
				filter(EXPIRES_PROP + " <", System.currentTimeMillis()).list();

		log.config(LogBuilder.createSystemMessage().
				addParameter("number of old sessions to delete from datastore", killList.size()).toString());

		try {
			for (Object o : killList) {
				Entity httpSessionEntity = (Entity) o;
				Key key = httpSessionEntity.getKey();
				// GAE does not use session id as key name, instead "_ahs<sessionId>"
				String sessionId = key.getName().substring(4);
				log.config(LogBuilder.createSystemMessage().
						addAction("delete session").
						addParameter("session id", sessionId).toString());
				Client client = UserManager.getInstance().getClientByHttpSessionId(sessionId);
				if (client != null && client instanceof Guest) {
					UserManager.getInstance().deleteClient(client);
				}
				OfyService.ofy().delete().entity(httpSessionEntity).now();
			}
			response.setStatus(HttpServletResponse.SC_OK);
		} catch (Exception e) {
			log.config(LogBuilder.createSystemMessage().
					addException("problem when deleting session and guest", e).toString());
			response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
		}
	}
}