Java tutorial
/* * This file is part of Alpine. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * Copyright (c) Steve Springett. All Rights Reserved. */ package alpine.persistence; import alpine.Config; import alpine.logging.Logger; import org.apache.commons.lang3.StringUtils; import org.h2.tools.Server; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; import java.sql.SQLException; /** * Initializes the embedded H2 database. This can be used as a configuration * store or as the main database for the application. * * Refer to {@link Config.AlpineKey#DATABASE_MODE} and application.properties for * additional details. * * @author Steve Springett * @since 1.0.0 */ public class PersistenceInitializer implements ServletContextListener { private static final Logger LOGGER = Logger.getLogger(PersistenceInitializer.class); private static Server dbServer; @Override public void contextInitialized(ServletContextEvent event) { startDbServer(); } @Override public void contextDestroyed(ServletContextEvent event) { stopDbServer(); } /** * Starts the H2 database engine if the database mode is set to 'server' */ private void startDbServer() { final String mode = Config.getInstance().getProperty(Config.AlpineKey.DATABASE_MODE); final int port = Config.getInstance().getPropertyAsInt(Config.AlpineKey.DATABASE_PORT); if (StringUtils.isEmpty(mode) || !("server".equals(mode) || "embedded".equals(mode) || "external".equals(mode))) { LOGGER.error("Database mode not specified. Expected values are 'server', 'embedded', or 'external'"); } if (dbServer != null || "embedded".equals(mode) || "external".equals(mode)) { return; } final String[] args = new String[] { "-tcp", "-tcpPort", String.valueOf(port), "-tcpAllowOthers", }; try { LOGGER.info("Attempting to start database service"); dbServer = Server.createTcpServer(args).start(); LOGGER.info("Database service started"); } catch (SQLException e) { LOGGER.error("Unable to start database service: " + e.getMessage()); stopDbServer(); } } /** * Stops the database server (if it was started). */ private void stopDbServer() { LOGGER.info("Shutting down database service"); if (dbServer != null) { dbServer.stop(); dbServer.shutdown(); } } }