AbstractStreamPersistence.java

/**
 * Copyright (C) 2008 - 2014 52°North Initiative for Geospatial Open Source
 * Software GmbH
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * If the program is linked with libraries which are licensed under one of
 * the following licenses, the combination of the program with the linked
 * library is not considered a "derivative work" of the program:
 *
 *     - Apache License, version 2.0
 *     - Apache Software License, version 1.0
 *     - GNU Lesser General Public License, version 3
 *     - Mozilla Public License, versions 1.0, 1.1 and 2.0
 *     - Common Development and Distribution License (CDDL), version 1.0
 *
 * Therefore the distribution of the program linked with libraries licensed
 * under the aforementioned licenses, is permitted by the copyright holders
 * if the distribution is compliant with both the GNU General Public
 * icense version 2 and the aforementioned licenses.
 *
 * This program 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.
 */
package org.n52.ses.persistency.streams;

import java.io.File;
import java.util.List;
import java.util.ServiceLoader;

import org.n52.ses.api.common.FreeResourceListener;
import org.n52.ses.api.event.MapEvent;
import org.n52.ses.api.event.PersistedEvent;
import org.n52.ses.api.ws.ISubscriptionManager;
import org.n52.ses.util.common.ConfigurationRegistry;

public abstract class AbstractStreamPersistence implements FreeResourceListener {

	private static final int MAX_EVENTS_DEFAULT = 5;

	public static AbstractStreamPersistence newInstance(ISubscriptionManager subMgr, File baseLocation) throws Exception {
		ServiceLoader<AbstractStreamPersistence> asps = ServiceLoader.load(AbstractStreamPersistence.class);
		
		if (baseLocation == null) {
			baseLocation = new File(AbstractStreamPersistence.class.getResource("/").getFile());
		}
		
		/*
		 * return the first available
		 */
		for (AbstractStreamPersistence abstractStreamPersistence : asps) {
			int maxEvents = MAX_EVENTS_DEFAULT;
			if (ConfigurationRegistry.isAvailable()) {
				ConfigurationRegistry.getInstance().registerFreeResourceListener(abstractStreamPersistence);
				Integer confEvents = ConfigurationRegistry.getInstance().getIntegerProperty(ConfigurationRegistry.MAX_PERSISTED_EVENTS);
				if (confEvents != null) {
					maxEvents = confEvents.intValue();
				}
			}
			
			abstractStreamPersistence.initialize(subMgr, baseLocation, maxEvents);

			return abstractStreamPersistence;
		}
		
		return null;
	}

	protected abstract void initialize(ISubscriptionManager subMgr, File baseLocation, int maxEvents) throws Exception;
	
	/**
	 * An implementation shall return the persisted events (count
	 * depends on the actual implementation) in the order
	 * it received it (timestamp ordered, early to late).
	 * 
	 * @return the list of persisted events, timestamp ordered
	 */
	public abstract List<PersistedEvent> getPersistedEvents();

	/**
	 * An implementation shall store the incoming event and
	 * return it as as list value of the {@link #getPersistedEvents()} method.
	 * 
	 * @param eve the event
	 * @param streamName 
	 */
	public abstract void persistEvent(MapEvent eve, String streamName);

	/**
	 * After calling this, the persisted events will be lost
	 * and all data related is deleted.
	 * 
	 * @throws Exception
	 */
	public abstract void destroy() throws Exception;
	
	/**
	 * free runtime resources
	 * 
	 * @throws Exception
	 */
	public abstract void shutdown() throws Exception;

	public abstract int getMaximumEventCount();
}