ShutdownServiceImpl.java

package org.apache.fulcrum.yaafi.service.shutdown;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import java.io.File;
import java.security.MessageDigest;

import org.apache.avalon.framework.activity.Disposable;
import org.apache.avalon.framework.activity.Initializable;
import org.apache.avalon.framework.activity.Startable;
import org.apache.avalon.framework.configuration.Configuration;
import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.avalon.framework.configuration.Reconfigurable;
import org.apache.avalon.framework.context.Context;
import org.apache.avalon.framework.context.ContextException;
import org.apache.avalon.framework.context.Contextualizable;
import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.apache.avalon.framework.service.ServiceException;
import org.apache.avalon.framework.service.ServiceManager;
import org.apache.avalon.framework.service.Serviceable;

/**
 * Monitors the componentConfiguration.xml and triggers a reconfiguration if the
 * content of the component configuration file has changed.
 *
 * @author <a href="mailto:siegfried.goeschl@it20one.at">Siegfried Goeschl</a>
 */

public class ShutdownServiceImpl extends AbstractLogEnabled implements ShutdownService, Serviceable, Contextualizable,
		Reconfigurable, Initializable, Runnable, Startable, Disposable {
	/** the interval between two checks in ms */
	private int interval;

	/** shall the worker thread terminate immediately */
	private boolean terminateNow;

	/** the worker thread polling the resource */
	private Thread workerThread;

	/** the ServiceManager to use */
	private ServiceManager serviceManager;

	/** the application directory */
	private File applicationDir;

	/** our own and only shutdown entry */
	private ShutdownEntry shutdownEntry;

	/////////////////////////////////////////////////////////////////////////
	// Avalon Service Lifecycle Implementation
	/////////////////////////////////////////////////////////////////////////

	/**
	 * Constructor
	 */
	public ShutdownServiceImpl() {
		this.terminateNow = false;
	}

	/**
	 * @see org.apache.avalon.framework.service.Serviceable#service(org.apache.avalon.framework.service.ServiceManager)
	 */
	public void service(ServiceManager manager) throws ServiceException {
		this.serviceManager = manager;
	}

	/**
	 * @see org.apache.avalon.framework.context.Contextualizable#contextualize(org.apache.avalon.framework.context.Context)
	 */
	public void contextualize(Context context) throws ContextException {
		this.applicationDir = (File) context.get("urn:avalon:home");
	}

	/**
	 * @see org.apache.avalon.framework.configuration.Configurable#configure(org.apache.avalon.framework.configuration.Configuration)
	 */
	public void configure(Configuration configuration) throws ConfigurationException {
		// limit to minimum interval of 1 second

		this.interval = Math.max(configuration.getAttributeAsInteger("interval", 5000), 1000);

		this.getLogger().debug("Monitoring the resources every " + this.interval + " ms");

		if (configuration.getChild("entry", false) != null) {
			Configuration shutdownConfig = configuration.getChild("entry");

			String shutdownEntryLocation = shutdownConfig.getChild("location").getValue();

			this.shutdownEntry = new ShutdownEntry(this.getLogger(), this.applicationDir, shutdownEntryLocation,
					shutdownConfig.getChild("useSystemExit").getValueAsBoolean(false));

			this.getLogger().debug("Using a shutdown entry : " + shutdownEntryLocation);
		} else {
			this.shutdownEntry = null;
			this.getLogger().debug("No shutdown entry defined");
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.apache.avalon.framework.activity.Initializable#initialize()
	 */
	public void initialize() throws Exception {

		// request a SHA-1 to make sure that it is supported
		MessageDigest.getInstance("SHA1");

		// check that the ServiceManager inplements Disposable
		if (this.serviceManager instanceof Disposable == false) {
			String msg = "The ServiceManager instance does not implement Disposable?!";
			throw new IllegalArgumentException(msg);
		}

		// create the worker thread polling the target
		this.workerThread = new Thread(this, "ShutdownService");
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.apache.avalon.framework.activity.Startable#start()
	 */
	public void start() throws Exception {
		this.getLogger().debug("Starting worker thread ...");
		this.workerThread.start();
	}

	/**
	 * @see org.apache.avalon.framework.activity.Startable#stop()
	 */
	public void stop() throws Exception {
		this.getLogger().debug("Stopping worker thread ...");
		this.terminateNow = true;
		this.workerThread.interrupt();
		this.workerThread.join(10000);
	}

	/**
	 * @see org.apache.avalon.framework.activity.Disposable#dispose()
	 */
	public void dispose() {
		this.terminateNow = false;
		this.applicationDir = null;
		this.workerThread = null;
		this.serviceManager = null;
	}

	/**
	 * @see org.apache.avalon.framework.configuration.Reconfigurable#reconfigure(org.apache.avalon.framework.configuration.Configuration)
	 */
	public void reconfigure(Configuration configuration) throws ConfigurationException {
		this.configure(configuration);
	}

	/////////////////////////////////////////////////////////////////////////
	// Service interface implementation
	/////////////////////////////////////////////////////////////////////////

	/* (non-Javadoc)
	 * @see java.lang.Runnable#run()
	 */
	public void run() {
		while (this.terminateNow == false) {
			try {
				Thread.sleep(this.interval);
			} catch (InterruptedException e) {
				// nothing to do
			}

			if (this.hasShutdownEntry() && this.getShutdownEntry().hasChanged()
					&& this.serviceManager instanceof Disposable) {

				if (this.getShutdownEntry().isUseSystemExit()) {
					this.getLogger().warn("Forcing a shutdown using System.exit() ...");
				} else {
					this.getLogger().warn("Forcing a shutdown ...");
				}

				// create a demon thread to shutdown the container
				Shutdown shutdown = new Shutdown((Disposable) this.serviceManager,
						this.getShutdownEntry().isUseSystemExit());

				Thread shutdownThread = new Thread(shutdown, "ShutdownServiceThread");
				shutdownThread.setDaemon(true);
				shutdownThread.start();
			}
		}
	}

	/////////////////////////////////////////////////////////////////////////
	// Service implementation
	/////////////////////////////////////////////////////////////////////////

	/**
	 * @return Returns the shutdownEntry.
	 */
	private ShutdownEntry getShutdownEntry() {
		return this.shutdownEntry;
	}

	/**
	 * @return Is a shutdown entry defined?
	 */
	private boolean hasShutdownEntry() {
		return (this.shutdownEntry != null ? true : false);
	}
}