Spring基础学习-任务执行二（TaskExecutor及Async）

一、Executor接口

1、顶层接口：Java JDK的package java.util.concurrent;包下的Executor接口

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/*
 *
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 *
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent;

/**
 * An object that executes submitted {@link Runnable} tasks. This
 * interface provides a way of decoupling task submission from the
 * mechanics of how each task will be run, including details of thread
 * use, scheduling, etc.  An {@code Executor} is normally used
 * instead of explicitly creating threads. For example, rather than
 * invoking {@code new Thread(new(RunnableTask())).start()} for each
 * of a set of tasks, you might use:
 *
 * 
 * Executor executor = anExecutor;
 * executor.execute(new RunnableTask1());
 * executor.execute(new RunnableTask2());
 * ...
 * 
 *
 * However, the {@code Executor} interface does not strictly
 * require that execution be asynchronous. In the simplest case, an
 * executor can run the submitted task immediately in the caller's
 * thread:
 *
 *  
 {@code
 * class DirectExecutor implements Executor {
 *   public void execute(Runnable r) {
 *     r.run();
 *   }
 * }}
 *
 * More typically, tasks are executed in some thread other
 * than the caller's thread.  The executor below spawns a new thread
 * for each task.
 *
 *  
 {@code
 * class ThreadPerTaskExecutor implements Executor {
 *   public void execute(Runnable r) {
 *     new Thread(r).start();
 *   }
 * }}
 *
 * Many {@code Executor} implementations impose some sort of
 * limitation on how and when tasks are scheduled.  The executor below
 * serializes the submission of tasks to a second executor,
 * illustrating a composite executor.
 *
 *  
 {@code
 * class SerialExecutor implements Executor {
 *   final Queue tasks = new ArrayDeque();
 *   final Executor executor;
 *   Runnable active;
 *
 *   SerialExecutor(Executor executor) {
 *     this.executor = executor;
 *   }
 *
 *   public synchronized void execute(final Runnable r) {
 *     tasks.offer(new Runnable() {
 *       public void run() {
 *         try {
 *           r.run();
 *         } finally {
 *           scheduleNext();
 *         }
 *       }
 *     });
 *     if (active == null) {
 *       scheduleNext();
 *     }
 *   }
 *
 *   protected synchronized void scheduleNext() {
 *     if ((active = tasks.poll()) != null) {
 *       executor.execute(active);
 *     }
 *   }
 * }}
 *
 * The {@code Executor} implementations provided in this package
 * implement {@link ExecutorService}, which is a more extensive
 * interface.  The {@link ThreadPoolExecutor} class provides an
 * extensible thread pool implementation. The {@link Executors} class
 * provides convenient factory methods for these Executors.
 *
 * 
Memory consistency effects: Actions in a thread prior to
 * submitting a {@code Runnable} object to an {@code Executor}
 * happen-before
 * its execution begins, perhaps in another thread.
 *
 * @since 1.5
 * @author Doug Lea
 */
public interface Executor {

    /**
     * Executes the given command at some time in the future.  The command
     * may execute in a new thread, in a pooled thread, or in the calling
     * thread, at the discretion of the {@code Executor} implementation.
     *
     * @param command the runnable task
     * @throws RejectedExecutionException if this task cannot be
     * accepted for execution
     * @throws NullPointerException if command is null
     */
    void execute(Runnable command);
}

2、spring的TaskExecutor接口继承自上面的Java JDK的Executor接口

/*
 * Copyright 2002-2012 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.util.concurrent.Executor;

/**
 * Simple task executor interface that abstracts the execution
 * of a {@link Runnable}.
 *
 * 
Implementations can use all sorts of different execution strategies,
 * such as: synchronous, asynchronous, using a thread pool, and more.
 *
 * 
Equivalent to JDK 1.5's {@link java.util.concurrent.Executor}
 * interface; extending it now in Spring 3.0, so that clients may declare
 * a dependency on an Executor and receive any TaskExecutor implementation.
 * This interface remains separate from the standard Executor interface
 * mainly for backwards compatibility with JDK 1.4 in Spring 2.x.
 *
 * @author Juergen Hoeller
 * @since 2.0
 * @see java.util.concurrent.Executor
 */
public interface TaskExecutor extends Executor {

	/**
	 * Execute the given {@code task}.
	 * 
The call might return immediately if the implementation uses
	 * an asynchronous execution strategy, or might block in the case
	 * of synchronous execution.
	 * @param task the {@code Runnable} to execute (never {@code null})
	 * @throws TaskRejectedException if the given task was not accepted
	 */
	@Override
	void execute(Runnable task);

}

3、都是spring的，interface AsyncTaskExecutor extends TaskExecutor

/*
 * Copyright 2002-2013 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.util.concurrent.Callable;
import java.util.concurrent.Future;

/**
 * Extended interface for asynchronous {@link TaskExecutor} implementations,
 * offering an overloaded {@link #execute(Runnable, long)} variant with a start
 * timeout parameter as well support for {@link java.util.concurrent.Callable}.
 *
 * 
Note: The {@link java.util.concurrent.Executors} class includes a set of
 * methods that can convert some other common closure-like objects, for example,
 * {@link java.security.PrivilegedAction} to {@link Callable} before executing them.
 *
 * 
Implementing this interface also indicates that the {@link #execute(Runnable)}
 * method will not execute its Runnable in the caller's thread but rather
 * asynchronously in some other thread.
 *
 * @author Juergen Hoeller
 * @since 2.0.3
 * @see SimpleAsyncTaskExecutor
 * @see org.springframework.scheduling.SchedulingTaskExecutor
 * @see java.util.concurrent.Callable
 * @see java.util.concurrent.Executors
 */
public interface AsyncTaskExecutor extends TaskExecutor {

	/** Constant that indicates immediate execution */
	long TIMEOUT_IMMEDIATE = 0;

	/** Constant that indicates no time limit */
	long TIMEOUT_INDEFINITE = Long.MAX_VALUE;


	/**
	 * Execute the given {@code task}.
	 * @param task the {@code Runnable} to execute (never {@code null})
	 * @param startTimeout the time duration (milliseconds) within which the task is
	 * supposed to start. This is intended as a hint to the executor, allowing for
	 * preferred handling of immediate tasks. Typical values are {@link #TIMEOUT_IMMEDIATE}
	 * or {@link #TIMEOUT_INDEFINITE} (the default as used by {@link #execute(Runnable)}).
	 * @throws TaskTimeoutException in case of the task being rejected because
	 * of the timeout (i.e. it cannot be started in time)
	 * @throws TaskRejectedException if the given task was not accepted
	 */
	void execute(Runnable task, long startTimeout);

	/**
	 * Submit a Runnable task for execution, receiving a Future representing that task.
	 * The Future will return a {@code null} result upon completion.
	 * @param task the {@code Runnable} to execute (never {@code null})
	 * @return a Future representing pending completion of the task
	 * @throws TaskRejectedException if the given task was not accepted
	 * @since 3.0
	 */
	Future submit(Runnable task);

	/**
	 * Submit a Callable task for execution, receiving a Future representing that task.
	 * The Future will return the Callable's result upon completion.
	 * @param task the {@code Callable} to execute (never {@code null})
	 * @return a Future representing pending completion of the task
	 * @throws TaskRejectedException if the given task was not accepted
	 * @since 3.0
	 */
	 Future submit(Callable task);

}

二 TaskExecutor接口

　　Spring的TaskExecutor接口等同于Java.util.concurrent.Executor接口。 实际上，它存在的主要原因是为了在使用线程池的时候，将对Java 5的依赖抽象出来。 这个接口只有一个方法execute(Runnable task)，它根据线程池的语义和配置，来接受一个执行任务。
　　最初创建TaskExecutor是为了在需要时给其他Spring组件提供一个线程池的抽象。 例如ApplicationEventMulticaster组件、JMS的AbstractMessageListenerContainer和对Quartz的整合都使用了TaskExecutor抽象来提供线程池。 当然，如果你的bean需要线程池行为，你也可以使用这个抽象层。

二 TaskExecutor类型

　　在Spring发行包中预定义了一些TaskExecutor实现。有了它们，你甚至不需要再自行实现了。

SimpleAsyncTaskExecutor 类：

这个实现不重用任何线程，或者说它每次调用都启动一个新线程。但是，它还是支持对并发总数设限，当超过线程并发总数限制时，阻塞新的调用，直到有位置被释放。如果你需要真正的池，请继续往下看。

SyncTaskExecutor类：

这个实现不会异步执行。相反，每次调用都在发起调用的线程中执行。它的主要用处是在不需要多线程的时候，比如简单的test case。

ConcurrentTaskExecutor 类：

这个实现是对Java 5 java.util.concurrent.Executor类的包装。有另一个备选, ThreadPoolTaskExecutor类，它暴露了Executor的配置参数作为bean属性。很少需要使用ConcurrentTaskExecutor, 但是如果ThreadPoolTaskExecutor不敷所需，         ConcurrentTaskExecutor是另外一个备选。

SimpleThreadPoolTaskExecutor 类：

这个实现实际上是Quartz的SimpleThreadPool类的子类，它会监听Spring的生命周期回调。当你有线程池，需要在Quartz和非Quartz组件中共用时，这是它的典型用处。

ThreadPoolTaskExecutor 类：

它不支持任何对java.util.concurrent包的替换或者下行移植。Doug Lea和Dawid Kurzyniec对java.util.concurrent的实现都采用了不同的包结构，导致它们无法正确运行。

这个实现只能在Java 5环境中使用，但是却是这个环境中最常用的。它暴露的bean properties可以用来配置一个 java.util.concurrent.ThreadPoolExecutor，把它包装到一个TaskExecutor中。如果你需要更加先进的类，比如ScheduledThreadPoolExecutor,我们建议你使用ConcurrentTaskExecutor来替代。

TimerTaskExecutor类：

这个实现使用一个TimerTask作为其背后的实现。它和SyncTaskExecutor的不同在于，方法调用是在一个独立的线程中进行的，虽然在那个线程中是同步的。

WorkManagerTaskExecutor类：

CommonJ 是BEA和IBM联合开发的一套规范。这些规范并非java ee的标准，但它是BEA和IBM的应用服务器实现的共同标准

这个实现使用了CommonJ WorkManager作为其底层实现，是在Spring context中配置CommonJ WorkManager应用的最重要的类。和SimpleThreadPoolTaskExecutor类似，这个类实现了WorkManager接口，因此可以直接作为WorkManager使用

三 TaskExcutor简单实例

1 taskExcutor

package com.test;

import org.springframework.core.task.TaskExecutor;

public class MainExecutor {
     private TaskExecutor taskExecutor;  
        public MainExecutor (TaskExecutor taskExecutor) {      
            this.taskExecutor = taskExecutor;    
        }  
        public void printMessages() {      
            for(int i = 0; i < 25; i++) {        
                taskExecutor.execute(new MessagePrinterTask("Message" + i));      
            }    
        }  
          
          
        private class MessagePrinterTask implements Runnable {      
            private String message;      
            public MessagePrinterTask(String message) {        
                this.message = message;      
            }      
            public void run() {        
                System.out.println(message);      
            }  
        } 
}

2 main

package com.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TaskTest {
    //本地测试，不用部署到tomcat
    public static void main(String[] args) {
        System.out.println("测试任务调度开始..."); 
        ApplicationContext appContext = new ClassPathXmlApplicationContext("applicationContext.xml");     
        MainExecutor te = (MainExecutor)appContext.getBean("taskExecutorExample");  
        te.printMessages();  
        System.out.println("--------"); 
    } 
}

3.applicationContext.xml配置