非阻塞线程池

注意：定制自己的线程池ThreadPoolExecutor管理类，除非对线程池特别了解，否则尽量不要使用，线上项目出现问题后难以维护

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class CustomThreadPoolExecutor {

	private ThreadPoolExecutor pool = null;
	
	/**
	 * 线程池初始化方法
	 * 
	 * corePoolSize 核心线程池大小----10
	 * maximumPoolSize 最大线程池大小----30
	 * keepAliveTime 线程池中超过corePoolSize数目的空闲线程最大存活时间----30+单位TimeUnit
	 * TimeUnit keepAliveTime时间单位----TimeUnit.MINUTES
	 * workQueue 阻塞队列----new ArrayBlockingQueue<Runnable>(10)====10容量的阻塞队列
	 * threadFactory 新建线程工厂----new CustomThreadFactory()====定制的线程工厂
	 * rejectedExecutionHandler 当提交任务数超过maxmumPoolSize+workQueue之和时,
	 * 							即当提交第41个任务时(前面线程都没有执行完,此测试方法中用sleep(100)),
	 * 						          任务会交给RejectedExecutionHandler来处理
	 */
	public void init() {
		pool = new ThreadPoolExecutor(
				10,
				30,
				30,
				TimeUnit.MINUTES,
				new ArrayBlockingQueue<Runnable>(10),
				new CustomThreadFactory(),
				new CustomRejectedExecutionHandler());
	}

	
	public void destory() {
		if(pool != null) {
			pool.shutdownNow();
		}
	}
	
	
	public ExecutorService getCustomThreadPoolExecutor() {
		return this.pool;
	}
	
	private class CustomThreadFactory implements ThreadFactory {

		private AtomicInteger count = new AtomicInteger(0);
		
		@Override
		public Thread newThread(Runnable r) {
			Thread t = new Thread(r);
			String threadName = CustomThreadPoolExecutor.class.getSimpleName() + count.addAndGet(1);
			System.out.println(threadName);
			t.setName(threadName);
			return t;
		}
	}
	
	
	private class CustomRejectedExecutionHandler implements RejectedExecutionHandler {

		@Override
		public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
			// 记录异常
			// 报警处理等
			System.out.println("error.............");
		}
	}
	
	
	
	// 测试构造的线程池
	public static void main(String[] args) {
		CustomThreadPoolExecutor exec = new CustomThreadPoolExecutor();
		// 1.初始化
		exec.init();
		
		ExecutorService pool = exec.getCustomThreadPoolExecutor();
		for(int i=1; i<100; i++) {
			System.out.println("提交第" + i + "个任务!");
			pool.execute(new Runnable() {
				@Override
				public void run() {
					try {
						Thread.sleep(3000);
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
					System.out.println("running=====");
				}
			});
		}
		
		
		
		// 2.销毁----此处不能销毁,因为任务没有提交执行完,如果销毁线程池,任务也就无法执行了
		// exec.destory();
		
		try {
			Thread.sleep(10000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}

方法中建立一个核心线程数为30个，缓冲队列有10个的线程池。每个线程任务，执行时会先睡眠3秒，保证提交10任务时，线程数目被占用完，再提交30任务时，阻塞队列被占用完，，这样提交第41个任务是，会交给CustomRejectedExecutionHandler 异常处理类来处理。

提交任务的代码如下：

public void execute(Runnable command) {
        if (command == null)
            throw new NullPointerException();
        /*
         * Proceed in 3 steps:
         *
         * 1. If fewer than corePoolSize threads are running, try to
         * start a new thread with the given command as its first
         * task.  The call to addWorker atomically checks runState and
         * workerCount, and so prevents false alarms that would add
         * threads when it shouldn't, by returning false.
         *
         * 2. If a task can be successfully queued, then we still need
         * to double-check whether we should have added a thread
         * (because existing ones died since last checking) or that
         * the pool shut down since entry into this method. So we
         * recheck state and if necessary roll back the enqueuing if
         * stopped, or start a new thread if there are none.
         *
         * 3. If we cannot queue task, then we try to add a new
         * thread.  If it fails, we know we are shut down or saturated
         * and so reject the task.
         */
        int c = ctl.get();
        if (workerCountOf(c) < corePoolSize) {
            if (addWorker(command, true))
                return;
            c = ctl.get();
        }
        if (isRunning(c) && workQueue.offer(command)) {
            int recheck = ctl.get();
            if (! isRunning(recheck) && remove(command))
                reject(command);
            else if (workerCountOf(recheck) == 0)
                addWorker(null, false);
        }
        else if (!addWorker(command, false))
            reject(command);
    }

注意：41以后提交的任务就不能正常处理了，因为，execute中提交到任务队列是用的offer方法，如上面代码，这个方法是非阻塞的，所以就会交给CustomRejectedExecutionHandler 来处理，所以对于大数据量的任务来说，这种线程池，如果不设置队列长度会OOM，设置队列长度，会有任务得不到处理，接下来我们构建一个阻塞的自定义线程池

定制属于自己的阻塞线程池

package com.tongbanjie.trade.test.commons;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class CustomThreadPoolExecutor {  
	  
      
    private ThreadPoolExecutor pool = null;  
      
      
    /** 
     * 线程池初始化方法 
     *  
     * corePoolSize 核心线程池大小----1 
     * maximumPoolSize 最大线程池大小----3 
     * keepAliveTime 线程池中超过corePoolSize数目的空闲线程最大存活时间----30+单位TimeUnit 
     * TimeUnit keepAliveTime时间单位----TimeUnit.MINUTES 
     * workQueue 阻塞队列----new ArrayBlockingQueue<Runnable>(5)====5容量的阻塞队列 
     * threadFactory 新建线程工厂----new CustomThreadFactory()====定制的线程工厂 
     * rejectedExecutionHandler 当提交任务数超过maxmumPoolSize+workQueue之和时, 
     *                          即当提交第41个任务时(前面线程都没有执行完,此测试方法中用sleep(100)), 
     *                                任务会交给RejectedExecutionHandler来处理 
     */  
    public void init() {  
        pool = new ThreadPoolExecutor(  
                1,  
                3,  
                30,  
                TimeUnit.MINUTES,  
                new ArrayBlockingQueue<Runnable>(5),  
                new CustomThreadFactory(),  
                new CustomRejectedExecutionHandler());  
    }  
  
      
    public void destory() {  
        if(pool != null) {  
            pool.shutdownNow();  
        }  
    }  
      
      
    public ExecutorService getCustomThreadPoolExecutor() {  
        return this.pool;  
    }  
      
    private class CustomThreadFactory implements ThreadFactory {  
  
        private AtomicInteger count = new AtomicInteger(0);  
          
        @Override  
        public Thread newThread(Runnable r) {  
            Thread t = new Thread(r);  
            String threadName = CustomThreadPoolExecutor.class.getSimpleName() + count.addAndGet(1);  
            System.out.println(threadName);  
            t.setName(threadName);  
            return t;  
        }  
    }  
      
      
    private class CustomRejectedExecutionHandler implements RejectedExecutionHandler {  
  
        @Override  
        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {  
        	try {
                                // 核心改造点，由blockingqueue的offer改成put阻塞方法
				executor.getQueue().put(r);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
        }  
    }  
      
      
      
    // 测试构造的线程池  
    public static void main(String[] args) {  
    	
        CustomThreadPoolExecutor exec = new CustomThreadPoolExecutor();  
        // 1.初始化  
        exec.init();  
          
        ExecutorService pool = exec.getCustomThreadPoolExecutor();  
        for(int i=1; i<100; i++) {  
            System.out.println("提交第" + i + "个任务!");  
            pool.execute(new Runnable() {  
                @Override  
                public void run() {  
                    try {  
                    	System.out.println(">>>task is running====="); 
                        TimeUnit.SECONDS.sleep(10);
                    } catch (InterruptedException e) {  
                        e.printStackTrace();  
                    }  
                }  
            });  
        }  
          
          
        // 2.销毁----此处不能销毁,因为任务没有提交执行完,如果销毁线程池,任务也就无法执行了  
        // exec.destory();  
          
        try {  
            Thread.sleep(10000);  
        } catch (InterruptedException e) {  
            e.printStackTrace();  
        }  
    }  
}  

解释：当提交任务被拒绝时，进入拒绝机制，我们实现拒绝方法，把任务重新用阻塞提交方法put提交，实现阻塞提交任务功能，防止队列过大，OOM，提交被拒绝方法在下面

  
public void execute(Runnable command) {
        if (command == null)
            throw new NullPointerException();

        int c = ctl.get();
        if (workerCountOf(c) < corePoolSize) {
            if (addWorker(command, true))
                return;
            c = ctl.get();
        }
        if (isRunning(c) && workQueue.offer(command)) {
            int recheck = ctl.get();
            if (! isRunning(recheck) && remove(command))
                reject(command);
            else if (workerCountOf(recheck) == 0)
                addWorker(null, false);
        }
        else if (!addWorker(command, false))
            // 进入拒绝机制， 我们把runnable任务拿出来，重新用阻塞操作put，来实现提交阻塞功能
            reject(command);
    }