EDIT

/**

 * Copyright (C) 2015 EDIT

 * European Distributed Institute of Taxonomy

 * http://www.e-taxonomy.eu

 *

 * The contents of this file are subject to the Mozilla Public License Version 1.1

 * See LICENSE.TXT at the top of this package for the full license terms.

 */

package eu.etaxonomy.cdm.vaadin.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import org.apache.log4j.Logger;

import com.vaadin.server.ServiceException;

import com.vaadin.server.SessionDestroyEvent;

import com.vaadin.server.SessionDestroyListener;

import com.vaadin.server.SessionInitEvent;

import com.vaadin.server.SessionInitListener;

import com.vaadin.server.VaadinSession;

import com.vaadin.spring.server.SpringVaadinServlet;

import eu.etaxonomy.cdm.api.conversation.ConversationHolder;

import eu.etaxonomy.cdm.vaadin.util.CdmSpringContextHelper;

import eu.etaxonomy.cdm.vaadin.util.DistributionEditorUtil;

/**

 * This class is part of the strategy to solve the lazy loading problem

 * and in more general to manage sessions properly.

 * <p>

 * Conversational Sessions essentially involve linking any UI which requires

 * long running sessions to a {@link CdmVaadinConversationalServlet}.

 * The servlet creates an instance of the ConversationHolder when a VaadinSession

 * is initialized and binds it on every service call, ensuring that a single

 * hibernate session is attached to a corresponding vaadin session.

 * <b>NOTE</b>: One major issue with this strategy is the bug (#4528) which

 * flushes the entire session even if a save / saveOrUpdate call is made on a

 * single CDM entity. This implies that this strategy is safe to use only in

 * 'session-save' UIs and not 'auto-save' UIs.

 *

 * @author c.mathew

 *

 */

public class CdmVaadinConversationalServlet extends SpringVaadinServlet implements SessionInitListener, SessionDestroyListener {

	private static final Logger logger = Logger.getLogger(CdmVaadinConversationalServlet.class);

	private static final long serialVersionUID = -2973231251266766766L;

	private ConversationHolder conversation;

	@Override

	protected void servletInitialized() throws ServletException {

		super.servletInitialized();

		getService().addSessionInitListener(this);

		getService().addSessionDestroyListener(this);

	}

	@Override

	public void sessionInit(SessionInitEvent event)

			throws ServiceException {

		conversation = (ConversationHolder) CdmSpringContextHelper.getCurrent().getBean("conversationHolder");

		conversation.bind();

		VaadinSession.getCurrent().setAttribute(DistributionEditorUtil.SATTR_CONVERSATION, conversation);

	}

	@Override

	public void sessionDestroy(SessionDestroyEvent event) {

		conversation.close();

	}

	@Override

	protected void service(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws ServletException, IOException {

		if(conversation != null) {

			logger.info("Servlet Service call - Binding Vaadin Session Conversation : " + conversation);

			conversation.bind();

		}

		super.service(request, response);

	}

}