Spring Framework example source code file (SimpleAsyncTaskExecutor.java)

This example Spring Framework source code file (SimpleAsyncTaskExecutor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

asynctaskexecutor, concurrencythrottleadapter, concurrencythrottleadapter, concurrencythrottlesupport, concurrencythrottlingrunnable, concurrencythrottlingrunnable, io, no_concurrency, runnable, runnable, serializable, simpleasynctaskexecutor, simpleasynctaskexecutor, string, timeout_immediate

The Spring Framework SimpleAsyncTaskExecutor.java source code

/*
 * Copyright 2002-2007 the original author or authors.
 *
 * 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.
 */

package org.springframework.core.task;

import java.io.Serializable;

import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ConcurrencyThrottleSupport;
import org.springframework.util.CustomizableThreadCreator;

/**
 * TaskExecutor implementation that fires up a new Thread for each task,
 * executing it asynchronously.
 *
 * <p>Supports limiting concurrent threads through the "concurrencyLimit"
 * bean property. By default, the number of concurrent threads is unlimited.
 *
 * <p>NOTE: This implementation does not reuse threads! Consider a
 * thread-pooling TaskExecutor implementation instead, in particular for
 * executing a large number of short-lived tasks.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see #setConcurrencyLimit
 * @see SyncTaskExecutor
 * @see org.springframework.scheduling.timer.TimerTaskExecutor
 * @see org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor
 * @see org.springframework.scheduling.commonj.WorkManagerTaskExecutor
 */
public class SimpleAsyncTaskExecutor extends CustomizableThreadCreator implements AsyncTaskExecutor, Serializable {

	/**
	 * Default thread name prefix: "SimpleAsyncTaskExecutor-".
	 * @deprecated as of Spring 2.0.3, since the default thread name prefix
	 * is now taken from the concrete class (could be a subclass)
	 */
	public static final String DEFAULT_THREAD_NAME_PREFIX =
			ClassUtils.getShortName(SimpleAsyncTaskExecutor.class) + "-";

	/**
	 * Permit any number of concurrent invocations: that is, don't throttle concurrency.
	 */
	public static final int UNBOUNDED_CONCURRENCY = ConcurrencyThrottleSupport.UNBOUNDED_CONCURRENCY;

	/**
	 * Switch concurrency 'off': that is, don't allow any concurrent invocations.
	 */
	public static final int NO_CONCURRENCY = ConcurrencyThrottleSupport.NO_CONCURRENCY;


	/**
	 * Internal concurrency throttle used by this executor.
	 */
	private final ConcurrencyThrottleAdapter concurrencyThrottle = new ConcurrencyThrottleAdapter();


	/**
	 * Create a new SimpleAsyncTaskExecutor with default thread name prefix.
	 */
	public SimpleAsyncTaskExecutor() {
		super();
	}

	/**
	 * Create a new SimpleAsyncTaskExecutor with the given thread name prefix.
	 * @param threadNamePrefix the prefix to use for the names of newly created threads
	 */
	public SimpleAsyncTaskExecutor(String threadNamePrefix) {
		super(threadNamePrefix);
	}


	/**
	 * Set the maximum number of parallel accesses allowed.
	 * -1 indicates no concurrency limit at all.
	 * <p>In principle, this limit can be changed at runtime,
	 * although it is generally designed as a config time setting.
	 * NOTE: Do not switch between -1 and any concrete limit at runtime,
	 * as this will lead to inconsistent concurrency counts: A limit
	 * of -1 effectively turns off concurrency counting completely.
	 * @see #UNBOUNDED_CONCURRENCY
	 */
	public void setConcurrencyLimit(int concurrencyLimit) {
		this.concurrencyThrottle.setConcurrencyLimit(concurrencyLimit);
	}

	/**
	 * Return the maximum number of parallel accesses allowed.
	 */
	public int getConcurrencyLimit() {
		return this.concurrencyThrottle.getConcurrencyLimit();
	}

	/**
	 * Return whether this throttle is currently active.
	 * @return <code>true if the concurrency limit for this instance is active
	 * @see #getConcurrencyLimit()
	 * @see #setConcurrencyLimit
	 */
	public boolean isThrottleActive() {
		return this.concurrencyThrottle.isThrottleActive();
	}


	/**
	 * Executes the given task, within a concurrency throttle
	 * if configured (through the superclass's settings).
	 * @see #doExecute(Runnable)
	 */
	public void execute(Runnable task) {
		execute(task, TIMEOUT_INDEFINITE);
	}

	/**
	 * Executes the given task, within a concurrency throttle
	 * if configured (through the superclass's settings).
	 * <p>Executes urgent tasks (with 'immediate' timeout) directly,
	 * bypassing the concurrency throttle (if active). All other
	 * tasks are subject to throttling.
	 * @see #TIMEOUT_IMMEDIATE
	 * @see #doExecute(Runnable)
	 */
	public void execute(Runnable task, long startTimeout) {
		Assert.notNull(task, "Runnable must not be null");
		if (isThrottleActive() && startTimeout > TIMEOUT_IMMEDIATE) {
			this.concurrencyThrottle.beforeAccess();
			doExecute(new ConcurrencyThrottlingRunnable(task));
		}
		else {
			doExecute(task);
		}
	}

	/**
	 * Template method for the actual execution of a task.
	 * <p>The default implementation creates a new Thread and starts it.
	 * @param task the Runnable to execute
	 * @see #createThread
	 * @see java.lang.Thread#start()
	 */
	protected void doExecute(Runnable task) {
		createThread(task).start();
	}


	/**
	 * Subclass of the general ConcurrencyThrottleSupport class,
	 * making <code>beforeAccess() and afterAccess()
	 * visible to the surrounding class.
	 */
	private static class ConcurrencyThrottleAdapter extends ConcurrencyThrottleSupport {

		protected void beforeAccess() {
			super.beforeAccess();
		}

		protected void afterAccess() {
			super.afterAccess();
		}
	}


	/**
	 * This Runnable calls <code>afterAccess() after the
	 * target Runnable has finished its execution.
	 */
	private class ConcurrencyThrottlingRunnable implements Runnable {

		private final Runnable target;

		public ConcurrencyThrottlingRunnable(Runnable target) {
			this.target = target;
		}

		public void run() {
			try {
				this.target.run();
			}
			finally {
				concurrencyThrottle.afterAccess();
			}
		}
	}

}