自定义线程池

╰+哭是因爲堅強的太久メ 2022-12-08 14:12 237阅读 0赞

自定义线程池的逻辑图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk5OTMyNw_size_16_color_FFFFFF_t_70_pic_center]

步骤如下：

1.首先定义BlockingQueue，实现`生产者消费者模式`，设置获取、添加任务的方法  
2.定义ThreadPool，设置核心数、池容量、阻塞队列对象、执行实体类等信息，实现execute方法  
3、测试。

package 并发工具;
    
    import lombok.extern.slf4j.Slf4j;
    
    import java.util.ArrayDeque;
    import java.util.Deque;
    import java.util.HashSet;
    import java.util.concurrent.TimeUnit;
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.ReentrantLock;
    
    @Slf4j(topic = "c.自定义线程池")
    public class 自定义线程池 {
        
        public static void main(String[] args) {
        
            ThreadPool threadPool = new ThreadPool(2,1000,TimeUnit.MILLISECONDS, 10);
            for (int i = 0; i < 5; i++) {
        
                int j = i;
                threadPool.execute(() -> {
        
                    log.debug("{}",j);
                });
            }
        }
    }
    
    @FunctionalInterface    //拒绝策略
    interface RejectPolicy<T>{
        
        void reject(BlockingQueue<T> queue,T task);
    }
    
    @Slf4j(topic = "c.ThreadPool")
    class ThreadPool{
        
        //任务队列
        private BlockingQueue<Runnable> taskQueue;
    
        //线程集合
        private HashSet<Worker> workers = new HashSet<>();
    
        //核心线程数
        private int coreSize;
    
        //获取任务超时时间
        private long timeout;
    
        private TimeUnit timeUnit;
    
        private RejectPolicy<Runnable> rejectPolicy;
    
        //执行任务
        public void execute(Runnable task){
        
            //当任务没有超过coreSize时，直接交给Worker对象执行
            //如果任务数超过了CoreSize，加入任务队列暂存
            synchronized (workers) {
        
                if(workers.size() < coreSize){
        
                    Worker worker = new Worker(task);
                    log.debug("新增 worker {}",worker);
                    workers.add(worker);
                    worker.start();
                } else{
        
                    log.debug("加入队列 {}",task);
                    taskQueue.put(task);
                    // 1) 死等
                    // 2) 带超时等待
                    // 3) 让调用者放弃任务执行
                    // 4) 让调用者抛出异常
                    // 5) 让调用者自己执行任务
                    //taskQueue.tryPut(rejectPolicy,task);
                }
            }
    
        }
    
        public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapacity) {
        
            this.coreSize = coreSize;
            this.timeout = timeout;
            this.timeUnit = timeUnit;
            this.taskQueue = new BlockingQueue<>(queueCapacity);
        }
    
        public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapacity, RejectPolicy<Runnable> rejectPolicy) {
        
            this.coreSize = coreSize;
            this.timeout = timeout;
            this.timeUnit = timeUnit;
            this.taskQueue = new BlockingQueue<>(queueCapacity);
            this.rejectPolicy = rejectPolicy;
        }
    
        class Worker extends Thread{
        
            private Runnable task;
    
            public Worker(Runnable task) {
        
                this.task = task;
            }
    
            @Override
            public void run() {
        
                //执行任务
                // 1) 当task不为空，执行任务
                // 2) 当task执行完毕，再接着从任务队列获取任务并执行
                while( task != null || (task = taskQueue.take()) != null){
        
                    try{
        
                        log.debug("正在执行....{}",task);
                        task.run();
                    } catch (Exception e){
        
                        e.printStackTrace();
                    }finally {
        
                        task = null;
                    }
                }
                synchronized (workers){
        
                    log.debug("work 被移除 {}",this);
                    workers.remove(this);
                }
            }
        }
    }
    
    
    //阻塞队列
    @Slf4j(topic = "c.BlockingQueue")
    class BlockingQueue<T> {
        
        // 1. 任务队列，双向链表
        private Deque<T> queue = new ArrayDeque<>();
    
        // 2. 锁
        private ReentrantLock lock = new ReentrantLock();
    
        // 3. 生产者条件变量
        private Condition fullWaitSet = lock.newCondition();
    
        // 4. 消费者条件变量
        private Condition emptyWaitSet = lock.newCondition();
    
        // 5. 容量
        private int capcity;
    
        public BlockingQueue(int capcity) {
        
            this.capcity = capcity;
        }
    
        // 带超时的阻塞获取
        public T poll(long timeout, TimeUnit unit){
        
            lock.lock();
            try {
        
                //将timeout统一转换为 纳秒
                long nanos = unit.toNanos(timeout);
                while(queue.isEmpty()){
        
                    try {
        
                        //返回的是剩余时间
                        if(nanos <= 0){
        
                            return null;
                        }
                        nanos = emptyWaitSet.awaitNanos(nanos);
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
                T t = queue.removeFirst();
                //唤醒等待的线程
                fullWaitSet.signal();
                return t;
            } finally {
        
                lock.unlock();
            }
        }
    
        // 阻塞获取
        public T take(){
        
            lock.lock();
            try {
        
                while(queue.isEmpty()){
        
                    try {
        
                        emptyWaitSet.await();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
                T t = queue.removeFirst();
                //唤醒等待的线程
                fullWaitSet.signal();
                return t;
            } finally {
        
                lock.unlock();
            }
        }
    
        // 阻塞添加
        public void put(T element){
        
            lock.lock();
            try {
        
                while(queue.size() == capcity){
        
                    try {
        
                        fullWaitSet.await();
                    } catch (InterruptedException e) {
        
                        e.printStackTrace();
                    }
                }
                queue.addLast(element);
                emptyWaitSet.signal();
            } finally {
        
                lock.unlock();
            }
        }
    
        // 带超时时间的阻塞添加
        public boolean offer(T task,long timeout,TimeUnit timeUnit){
        
            lock.lock();
            try {
        
                long nanos = timeUnit.toNanos(timeout);
                while(queue.size() == capcity){
        
                    try{
        
                        log.debug("等待加入任务队列 {} ....",task);
                        if(nanos <= 0){
        
                            return false;
                        }
                        nanos = fullWaitSet.awaitNanos(nanos);
                    } catch (Exception e){
        
                        e.printStackTrace();
                    }
                }
                log.debug("加入任务队列 {}",task);
                queue.addLast(task);
                emptyWaitSet.signal();
                return true;
            } finally {
        
                lock.unlock();
            }
        }
    
        //获取大小
        public int size(){
        
            lock.lock();
            try{
        
                return queue.size();
            } finally {
        
                lock.unlock();
            }
        }
    
    
        public void tryPut(RejectPolicy<T> rejectPolicy, T task) {
        
            lock.lock();
            try{
        
                //判断队列是否满
                if(queue.size() == capcity){
        
                    rejectPolicy.reject(this,task);
                } else {
        
                    log.debug("加入任务队列 {}",task);
                    queue.addLast(task);
                    emptyWaitSet.signal();
                }
            } finally {
        
                lock.unlock();
            }
        }
    }

输出：

17:37:56.216 [main] DEBUG c.ThreadPool - 新增 worker Thread[Thread-0,5,main]
    17:37:56.223 [main] DEBUG c.ThreadPool - 新增 worker Thread[Thread-1,5,main]
    17:37:56.223 [Thread-0] DEBUG c.ThreadPool - 正在执行....并发工具.自定义线程池$$Lambda$1/2036368507@2231df33
    17:37:56.223 [main] DEBUG c.ThreadPool - 加入队列 并发工具.自定义线程池$$Lambda$1/2036368507@1f89ab83
    17:37:56.224 [Thread-0] DEBUG c.自定义线程池 - 0
    17:37:56.224 [Thread-1] DEBUG c.ThreadPool - 正在执行....并发工具.自定义线程池$$Lambda$1/2036368507@166b3cbc
    17:37:56.224 [main] DEBUG c.ThreadPool - 加入队列 并发工具.自定义线程池$$Lambda$1/2036368507@e73f9ac
    17:37:56.224 [Thread-0] DEBUG c.ThreadPool - 正在执行....并发工具.自定义线程池$$Lambda$1/2036368507@1f89ab83
    17:37:56.224 [Thread-1] DEBUG c.自定义线程池 - 1
    17:37:56.224 [main] DEBUG c.ThreadPool - 加入队列 并发工具.自定义线程池$$Lambda$1/2036368507@61064425
    17:37:56.225 [Thread-0] DEBUG c.自定义线程池 - 2
    17:37:56.225 [Thread-1] DEBUG c.ThreadPool - 正在执行....并发工具.自定义线程池$$Lambda$1/2036368507@e73f9ac
    17:37:56.225 [Thread-0] DEBUG c.ThreadPool - 正在执行....并发工具.自定义线程池$$Lambda$1/2036368507@61064425
    17:37:56.225 [Thread-1] DEBUG c.自定义线程池 - 3
    17:37:56.225 [Thread-0] DEBUG c.自定义线程池 - 4

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mzk5OTMyNw_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/23d9ea42be1e4b6299ef75e4a0ef478b.png