OutOfMemoryErrorHandler.java

/*
 * Copyright (C) 2011 Stefan Willinger
 * wis775@users.sourceforge.net
 *
 * 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.
 *
 * 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.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package net.sourceforge.squirrel_sql.client;

import net.sourceforge.squirrel_sql.client.session.ISession;
import net.sourceforge.squirrel_sql.client.session.SessionManager;
import net.sourceforge.squirrel_sql.fw.util.StringManager;
import net.sourceforge.squirrel_sql.fw.util.StringManagerFactory;
import net.sourceforge.squirrel_sql.fw.util.log.ILogger;
import net.sourceforge.squirrel_sql.fw.util.log.LoggerController;

/**
 * Handler, that tries to free some memory. Mostly, if a
 * {@link OutOfMemoryError} occurs,the user not be able to save his work,
 * because the GUI is no longer responsible. To avoid this, we try to free some
 * memory by closing all SQL result tabs. Under normal conditions, the SQL
 * result tabs are components, which uses the most memory. So we have a high
 * chance to free enough memory to keep the GUI responsible, that the user can
 * save his work and restart SQuirrel. The scope is not, to protect the user
 * from getting a {@link OutOfMemoryError}.
 * 
 * @author Stefan Willinger
 * 
 */
public class OutOfMemoryErrorHandler implements IOutOfMemoryErrorHandler{

	private static final ILogger log = LoggerController.createLogger(OutOfMemoryErrorHandler.class);

	private static final StringManager stringMgr = StringManagerFactory
			.getStringManager(OutOfMemoryErrorHandler.class);

	interface i18n {
		String message = stringMgr.getString("OutOfMemoryErrorHandler.message");
	}


	/**
	 * The application
	 */
	private IApplication application;

	/**
	 * Default Constructor. You have to set {@link #application} manually.
	 */
	public OutOfMemoryErrorHandler() {
		super();
	}

	/**
	 * Constructor setting the {@link #application}
	 * 
	 * @param application
	 */
	public OutOfMemoryErrorHandler(IApplication application) {
		super();
		setApplication(application);
	}

	
	/**
	 * Gets the application
	 * 
	 * @return the application
	 */
	public IApplication getApplication() {
		return application;
	}

	/**
	 * Sets the application.
	 * 
	 * @param application
	 *            the application to set
	 * @throws IllegalArgumentException
	 *             if application is null;
	 */
	public void setApplication(IApplication application) {
		if (application == null) {
			throw new IllegalArgumentException("application must not be null");
		}
		this.application = application;
	}

	/**
	 * To free some memory, close all SQL result-tabs of all current sessions.
	 * This may free some memory.
	 * @see net.sourceforge.squirrel_sql.client.IOutOfMemoryErrorHandler#handleOutOfMemoryError()
	 */
	public synchronized void handleOutOfMemoryError() {

		SessionManager sessionManager = application.getSessionManager();

		// All sessions, the user has opened
		ISession[] sessions = sessionManager.getConnectedSessions();

		if (sessions.length != 0) {
			for (ISession session : sessions) {
				closeResultTabs(session);
			}
			showMessage(sessionManager);
		} else {
			log.info("A OutOfMemoryError occured, but there are no sessions connected - so we cann't free memory.");
		}

	}

	/**
	 * Inform the user, that a {@link OutOfMemoryError} had occurred.
	 * 
	 * @param sessionManager
	 *            the sessionManager
	 */
	private void showMessage(SessionManager sessionManager) {
		ISession activeSession = sessionManager.getActiveSession();
		if (activeSession != null) {
			log.info(i18n.message);
			activeSession.showErrorMessage(i18n.message);
			application.showErrorDialog(i18n.message);
		} else {
			log.info("A OutOfMemoryError occured, but there are no active session!");
		}
	}

	/**
	 * Close all result tabs of the session.
	 * 
	 * @param session
	 *            the session, where to close the result tabs.
	 */
	private void closeResultTabs(ISession session) {
		session.getSessionInternalFrame().getSQLPanelAPI().closeAllSQLResultTabs();
	}
	
}