communicationhandler.java

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/**
 * $Log: CommunicationHandler.java,v $
 * Revision 1.2  2003/02/03 13:03:35  mwulff
 * now calls streamWrapper.closeConnection() in followUpConnection()
 *
 * Revision 1.1  2003/01/16 13:12:40  mwulff
 * initial version
 *
 * Revision 1.6  2002/12/20 18:52:25  mwulff
 * no message
 *
 * Revision 1.5  2002/12/15 16:55:07  mwulff
 * adjusted to reorganisation of the client logging system
 *
 * Revision 1.4  2002/12/13 20:08:35  mwulff
 * no message
 *
 * Revision 1.3  2002/12/05 21:33:50  mwulff
 * reengineering of the complete communication component
 *
 * Revision 1.2  2002/12/01 13:02:14  mwulff
 * accomodated to ClientResourceManager and ClientLoggingManager,
 * that are now implemented as singleton
 *
 * Revision 1.1  2002/11/22 16:42:45  mwulff
 * moved
 *
 * Revision 1.2  2002/11/08 19:23:04  mwulff
 * updated to handle remote garbage collection
 *
 * Revision 1.1  2002/11/05 19:46:51  mwulff
 * initial version
 *
 */
package de.fhm.jkf.comm.cl;

import java.io.IOException;
import java.net.URL;
import java.util.Vector;

import de.fhm.jkf.comm.clsv.CompressionHandler;
import de.fhm.jkf.comm.clsv.Request;
import de.fhm.jkf.comm.clsv.Response;
import de.fhm.jkf.comm.clsv.ResponseCommands;
import de.fhm.jkf.resource.cl.ClientResourceManager;

/**
 * <br><br><center><table border="1" width="80%"><hr>
 * <strong><a href="http://jkf.sourceforge.net">The JKF Project</a></strong>
 * <p>
 * Copyright (C) 2002 by Marten Wulff
 * <p>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p>
 * 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
 * Lesser General Public License for more details.
 * <p>
 * You should have received a copy of the <a href="http://www.gnu.org/copyleft/lesser.html">
 * GNU Lesser General Public License</a> along with this library; if not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA  02111-1307  USA
 * <hr></table></center>
 * 
 * 
 * <p>
 * <code>CommunicationHandler</code> is the abstract parent class of 
 * all client side classes, that communicate with the server. This class
 * is responsible for handling the client side connection to the server.
 * Therefore is used a <code>URLConnection</code>. Also handling of client
 * logging messages, that should be transfered to the server, and remote
 * garbage collection is done by this class.
 * If any <code>ResponseCommands</code> are received from the server, they
 * are delegated to the <code>ClientResourceManager</code>.
 * </p>
 * 
 * @see java.net.URLConnection 
 * @see de.fhm.jkf.resource.cl.ClientResourceManager
 * 
 * @author		marten wulff
 * @version 	1.0
 */
abstract class CommunicationHandler {

	// reference to the singlton RemoteLogBuffer
	protected static RemoteLogBuffer logBuffer = RemoteLogBuffer.instance();

	// reference to the singleton RemoteGCBuffer
	protected static RemoteGCBuffer gcBuffer = RemoteGCBuffer.instance();

	// Reference to the ClientResourceManger
	protected static ClientResourceManager resManager =
		ClientResourceManager.instance();

	// Reference to the SessionManager
	protected static SessionManager sessionManager = SessionManager.instance();

	// URL for the RequestBrokerServlet
	protected URL requestBrokerServlet = null;

	// CompressionHandler that is used to enable compressed data transer
	protected CompressionHandler compressionHandler = null;
	protected URLConnectionStreamWrapper wrapper = null;

	/**
	 * Constructor for CommunicationHandler.
	 */
	CommunicationHandler() {
		super();

		requestBrokerServlet = resManager.getRequestBrokerURL();
		compressionHandler =
			new ClientCompressionHandler(
				resManager.getCompressLimit(),
				resManager.getCommunicationBufferSize());
	}

	/**
	 * Method for adding available log messages to the client
	 * request. All LoggingEvents stored in the RemoteLogBuffer
	 * are retrieved and added to the request.
	 * 
	 * @param request the Request which is send to the server
	 */
	void handleLogMessages(Request request) {
		// let's see if there are any log messages we can send 
		// to the server
		Vector logs = logBuffer.getLogMessages();
		if (logs.size() > 0) {
			request.setLogMessages(logs);
		}

	}

	/**
	 * Method for adding available gc messages to the client
	 * request. 
	 * 
	 * @param request the Request which will be send to the server
	 */
	void handleGCMessages(Request request) {
		// let's see if there are any remote objects that
		// should be handled by the remote garbage collection
		Vector gcObjects = gcBuffer.getGCMessages();
		if (gcObjects.size() > 0) {
			request.setGCMessages(gcObjects);
		}
	}

	/**
	 * Method for openning a connection to the server. Thereby is 
	 * handled transferation of client logging events and remote garbage
	 * collection.
	 * 
	 * @param request 	the Request that is send to the server
	 * 
	 * @see de.fhm.jkf.comm.clsv.Request
	 * 
	 * @throws IOException if any I/O-Error occures
	 */
	void prepareConnection(Request request) throws IOException {

		// let's see if there are any log messages we can send 
		// to the server
		handleLogMessages(request);

		// are there any objects for the remote garbage collection ??
		handleGCMessages(request);

		wrapper =
			new URLConnectionStreamWrapper(
				this.requestBrokerServlet.openConnection());
		wrapper.setSessionInfo(sessionManager.getSessionInfo());

		compressionHandler.setStreamWrapper(wrapper);
	}

	/**
	 * This method does all the work, that has to be done after a 
	 * server request. Right at the moment there is only a check
	 * if the server transfered some <code>ResponseCommands</code>.
	 * If available the <code>ResponseCommands</code> are delegated
	 * to the <code>ClientResourceManager</code>.
	 * 
	 * @param response 	the response from the last server connection
	 */
	void followUpConnection(Response response) {
		ResponseCommands commands = response.getResponseCommands();
		if (commands != null) {
			resManager.interpretResponseCommands(commands);
		}
		
		wrapper.closeConnection();
	}
}