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jBasics is a collection of useful utility classes for Java. This includes helper for XML, mathematic functions, restful web services helper, pattern oriented programming interfaces and more. Currently Java7 and up is supported. Version 1.0 will required at leaset Java8.

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/*
 * Copyright (c) 2009-2015
 * 	IT-Consulting Stephan Schloepke (http://www.schloepke.de/)
 * 	klemm software consulting Mirko Klemm (http://www.klemm-scs.com/)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.jbasics.jee.servlet;

import org.jbasics.checker.ContractCheck;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * The {@link ServletExecutorPool} is designed specific for use in a servlet containter. You need to register the {@link
 * ServletExecutorPool} as a {@link ServletContextListener} in the web.xml in order to function correctly.  Currently
 * not finished yet! So this is in alpha, beta or what so ever 
 *
 * @author Stephan Schloepke
 * @since 1.0
 */
public class ServletExecutorPool implements ServletContextListener {
	private final static AtomicBoolean available = new AtomicBoolean(false);
	private final static ConcurrentMap, ExecutorService> executors = new ConcurrentHashMap, ExecutorService>();

	public static  Future queueTask(final Enum name, final Callable task) {
		return ServletExecutorPool.getOrCreateExecutorService(name).submit(ContractCheck.mustNotBeNull(task, "task")); //$NON-NLS-1$
	}

	/**
	 * Returns an already created {@link ExecutorService} for the given name or creates one and returns it.
	 *
	 * @param name The name of the executor pool to create
	 *
	 * @return The {@link ExecutorService} already created or a newly created one.
	 */
	protected final static ExecutorService getOrCreateExecutorService(final Enum name) {
		if (!ServletExecutorPool.available.get()) {
			throw new IllegalStateException("Executor is no longer available (terminating or is terminated)"); //$NON-NLS-1$
		}
		ExecutorService result = ServletExecutorPool.executors.get(ContractCheck.mustNotBeNull(name, "name")); //$NON-NLS-1$
		if (result == null) {
			result = Executors.newSingleThreadExecutor();
			ExecutorService t = ServletExecutorPool.executors.putIfAbsent(name, result);
			if (t != null) {
				result.shutdown();
				result = t;
			}
		}
		return result;
	}

	public void contextInitialized(final ServletContextEvent sce) {
		ServletExecutorPool.available.set(false);
	}

	public void contextDestroyed(final ServletContextEvent sce) {
		ServletExecutorPool.shutdownAll();
	}

	public static void shutdownAll() {
		if (ServletExecutorPool.available.compareAndSet(true, false)) {
			for (ExecutorService service : ServletExecutorPool.executors.values()) {
				try {
					service.shutdown();
				} catch (RuntimeException e) {
					// ignore this here
				}
			}
			long startTime = System.currentTimeMillis();
			long timeWait = 120; // Seconds
			for (ExecutorService service : ServletExecutorPool.executors.values()) {
				long timeUsed = System.currentTimeMillis() - startTime;
				if (timeUsed > 0) {
					timeUsed = timeUsed / 1000;
				}
				timeWait -= timeUsed;
				try {
					if (timeWait <= 0) {
						service.awaitTermination(5, TimeUnit.SECONDS);
					} else {
						service.awaitTermination(timeWait, TimeUnit.SECONDS);
					}
				} catch (InterruptedException e) {
					// Ignore
				}
				if (!service.isTerminated()) {
					service.shutdownNow();
				}
			}
		}
	}
}