SimpleThreadPool给线程池增加拒绝策略和停止方法

Posted 2021-03-20 zheaven

给线程池增加拒绝策略和停止方法

package com.dwz.concurrency.chapter13;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class SimpleThreadPool3 {
    private final int size;
    private final int queueSize;
    private final static int DEFAULT_SIZE = 10;
    private final static int DEFAULT_TASK_QUEUE_SIZE = 2000;
    private static volatile int seq = 0;
    private final static String THREAD_PREFIX = "SIMPLE_THREAD_POOL-";
    private final static ThreadGroup GROUP = new ThreadGroup("Pool_Group");
    private final static LinkedList<Runnable> TASK_QUEUE = new LinkedList<>();
    private final static List<WorkerTask> THREAD_QUEUE = new ArrayList<>();
    private final DiscardPolicy discardPolicy;
    private final static DiscardPolicy DEFAULT_DISCARD_POLICY = ()->{
        throw new DiscardException("Discard this task.");
    };
    private volatile boolean destroy = false;

    public SimpleThreadPool3() {
        this(DEFAULT_SIZE, DEFAULT_TASK_QUEUE_SIZE, DEFAULT_DISCARD_POLICY);
    }

    public SimpleThreadPool3(int size, int queueSize, DiscardPolicy discardPolicy) {
        this.size = size;
        this.queueSize = queueSize;
        this.discardPolicy = discardPolicy;
        init();
    }

    private void init() {
        for (int i = 0; i < this.size; i++) {
            createWorkTask();
        }
    }

    public void submit(Runnable runnable) {
        if(destroy) {
            throw new IllegalStateException("The thread pool already destroy and not allow submit task.");
        }
        synchronized (TASK_QUEUE) {
            if(TASK_QUEUE.size() >= this.queueSize) {
                discardPolicy.discard();
            }
            TASK_QUEUE.addLast(runnable);
            TASK_QUEUE.notifyAll();
        }
    }

    private void createWorkTask() {
        WorkerTask task = new WorkerTask(GROUP, THREAD_PREFIX + (seq++));
        task.start();
        THREAD_QUEUE.add(task);
    }
    
    public void shutdown() throws InterruptedException {
        while (!TASK_QUEUE.isEmpty()) {
            Thread.sleep(50);
        }
        int initVal = THREAD_QUEUE.size();
        while (initVal > 0) {
            for(WorkerTask task : THREAD_QUEUE) {
                if(task.getTaskState() == TaskState.BLOCKED) {
                    task.interrupt();
                    task.close();
                    initVal--;
                } else {
                    Thread.sleep(10);
                }
            }
        }
        this.destroy = true;
        System.out.println("The thread pool disposed.");
    }
    
    public int getSize() {
        return size;
    }

    public int getQueueSize() {
        return queueSize;
    }
    
    public boolean destroy() {
        return destroy;
    }
    
    private enum TaskState {
        FREE, RUNNING, BLOCKED, DEAD
    }
    
    public static class DiscardException extends RuntimeException {

        public DiscardException(String message) {
            super(message);
        }
    }
    
    public interface DiscardPolicy{
        void discard() throws DiscardException;
    }
    
    private static class WorkerTask extends Thread {
        private volatile TaskState taskState = TaskState.FREE;

        public WorkerTask(ThreadGroup group, String name) {
            super(group, name);
        }

        public TaskState getTaskState() {
            return this.taskState;
        }

        @Override
        public void run() {
            OUTER: 
            while (this.taskState != TaskState.DEAD) {
                Runnable runnable = null;
                synchronized (TASK_QUEUE) {
                    while (TASK_QUEUE.isEmpty()) {
                        try {
                            this.taskState = TaskState.BLOCKED;
                            TASK_QUEUE.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                            // 线程被打断回到OUTER位置
                            break OUTER;
                        }
                    }
                    runnable = TASK_QUEUE.removeFirst();
                }
                
                if (runnable != null) {
                    System.out.println("runnable into...");
                    this.taskState = TaskState.RUNNING;
                    runnable.run();
                    this.taskState = TaskState.FREE;
                }
            }
        }

        public void close() {
            this.taskState = TaskState.DEAD;
        }
    }

    public static void main(String[] args) throws InterruptedException {
        SimpleThreadPool3 threadPool = new SimpleThreadPool3();
//        IntStream.range(0, 40).forEach(i -> {
//            threadPool.submit(() -> {
//                System.out.println("The runnable " + i + " be serviced by " + Thread.currentThread() + " start.");
//                try {
//                    Thread.sleep(1000);
//                } catch (InterruptedException e) {
//                    e.printStackTrace();
//                }
//                System.out.println("The runnable " + i + " be serviced by " + Thread.currentThread() + " finished.");
//            });
//        });
        for(int i = 0; i < 40; i++) {
            threadPool.submit(() -> {
                System.out.println("The runnable be serviced by " + Thread.currentThread() + " start.");
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("The runnable be serviced by " + Thread.currentThread() + " finished.");
            });
        }
        
        Thread.sleep(10_000);
        threadPool.shutdown();
        threadPool.submit(()->{System.out.println("=======================");});
    }
}