Java tutorial
/******************************************************************************* * This file is part of OpenNMS(R). * * Copyright (C) 2012 The OpenNMS Group, Inc. * OpenNMS(R) is Copyright (C) 1999-2012 The OpenNMS Group, Inc. * * OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc. * * OpenNMS(R) is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published * by the Free Software Foundation, either version 3 of the License, * or (at your option) any later version. * * OpenNMS(R) 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with OpenNMS(R). If not, see: * http://www.gnu.org/licenses/ * * For more information contact: * OpenNMS(R) Licensing <license@opennms.org> * http://www.opennms.org/ * http://www.opennms.com/ *******************************************************************************/ package org.opennms.ng.services.eventconfig; import java.io.File; import java.io.IOException; import org.exolab.castor.xml.MarshalException; import org.exolab.castor.xml.ValidationException; import org.opennms.core.utils.ConfigFileConstants; import org.opennms.core.xml.CastorUtils; import org.opennms.netmgt.config.archiver.events.EventsArchiverConfiguration; import org.springframework.core.io.FileSystemResource; /** * This is the singleton class used to load the configuration for the OpenNMS * Events Archiver from the events-archiver-configuration xml file. * * <strong>Note: </strong>Users of this class should make sure the * <em>init()</em> is called before calling any other method to ensure the * config is loaded before accessing other convenience methods. * * @author <a href="mailto:sowmya@opennms.org">Sowmya Nataraj </a> * @author <a href="http://www.opennms.org/">OpenNMS </a> */ public final class EventsArchiverConfigFactory { /** * The singleton instance of this factory */ private static EventsArchiverConfigFactory m_singleton = null; /** * The config class loaded from the config file */ private EventsArchiverConfiguration m_config; /** * This member is set to true if the configuration file has been loaded. */ private static boolean m_loaded = false; /** * Private constructor * * @exception java.io.IOException * Thrown if the specified config file cannot be read * @exception org.exolab.castor.xml.MarshalException * Thrown if the file does not conform to the schema. * @exception org.exolab.castor.xml.ValidationException * Thrown if the contents do not match the required schema. */ private EventsArchiverConfigFactory(String configFile) throws IOException, MarshalException, ValidationException { m_config = CastorUtils.unmarshal(EventsArchiverConfiguration.class, new FileSystemResource(configFile)); } /** * Load the config from the default config file and create the singleton * instance of this factory. * * @exception java.io.IOException * Thrown if the specified config file cannot be read * @exception org.exolab.castor.xml.MarshalException * Thrown if the file does not conform to the schema. * @exception org.exolab.castor.xml.ValidationException * Thrown if the contents do not match the required schema. * @throws java.io.IOException if any. * @throws org.exolab.castor.xml.MarshalException if any. * @throws org.exolab.castor.xml.ValidationException if any. */ public static synchronized void init() throws IOException, MarshalException, ValidationException { if (m_loaded) { // init already called - return // to reload, reload() will need to be called return; } File cfgFile = ConfigFileConstants.getFile(ConfigFileConstants.EVENTS_ARCHIVER_CONFIG_FILE_NAME); m_singleton = new EventsArchiverConfigFactory(cfgFile.getPath()); m_loaded = true; } /** * Reload the config from the default config file * * @exception java.io.IOException * Thrown if the specified config file cannot be read/loaded * @exception org.exolab.castor.xml.MarshalException * Thrown if the file does not conform to the schema. * @exception org.exolab.castor.xml.ValidationException * Thrown if the contents do not match the required schema. * @throws java.io.IOException if any. * @throws org.exolab.castor.xml.MarshalException if any. * @throws org.exolab.castor.xml.ValidationException if any. */ public static synchronized void reload() throws IOException, MarshalException, ValidationException { m_singleton = null; m_loaded = false; init(); } /** * Return the singleton instance of this factory. * * @return The current factory instance. * @throws IllegalStateException * Thrown if the factory has not yet been initialized. */ public static synchronized EventsArchiverConfigFactory getInstance() { if (!m_loaded) throw new IllegalStateException("The factory has not been initialized"); return m_singleton; } /** * Return the archive age. Note: events created before this time are to be * removed. * * @return the archive age of events */ public synchronized String getArchiveAge() { return m_config.getArchiveAge(); } /** * Return the seperator to be used between column values in the archive * file. * * @return the seperator to be used between column values in the archive * file */ public synchronized String getSeparator() { return m_config.getSeparator(); } }