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线程池核心参数配置
最近更新：2025-06-10   |   字数总计：1.4k   |   阅读估时：7分钟   |   阅读量：次

理清问题：

1.JVM的线程池中到达核心线程数之后什么情况才会创建线程到达最大线程数（tip：tomcat线程池与JVM线程池有所不同）

先将任务放入队列，队列满了再创建线程直到最大线程数，最后再触发拒绝策略

2.线程处理任务队列中任务的顺序

FIFO

示例代码

tips: 最大线程数这个参数是跟任务队列相关的，如果任务队列是无界队列，则该参数不生效。

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package com.path.service;

import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;

@Slf4j
public class ExecutorConfiguration {

    public static void main(String[] args) throws InterruptedException {

        // 提交任务流程：1. 没有空闲线程且未到核心线程数，则创建线程
        //            2. 到达核心线程数，则将任务添加到队列中
        //            3. 任务队列满了，并且线程还未达到最大线程数，则继续创建线程来处理新增的任务
        //            4. 线程处理完任务后，再到任务队列中获取任务处理
        int corePoolSize = 5;
        int maximumPoolSize = 10;
        int taskCount = 16;
        ThreadPoolExecutor threadPoolExecutor =
                new ThreadPoolExecutor(corePoolSize, maximumPoolSize, 60L, TimeUnit.SECONDS, new CustomQueue<>(5),
                        new CustomThreadFactory(), new ThreadPoolExecutor.AbortPolicy());

        CountDownLatch countDownLatch = new CountDownLatch(taskCount);
        for (int i = 1; i <= taskCount; i++) {
            Thread.sleep(60);
            int finalI = i;
            try {
                threadPoolExecutor.submit(()-> {
                    try {
                        Thread.sleep(1000);
                        log.info("thread name :{} , handler task id: {}", Thread.currentThread().getName(), finalI);
                        countDownLatch.countDown();
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                });
            } catch (RejectedExecutionException e) {
                log.error("thread pool reject task, task id :{}", finalI);
                countDownLatch.countDown();
            }
        }

        countDownLatch.await();
        threadPoolExecutor.shutdownNow();
    }

    /**
     * 自定义线程的工厂类，来监听线程的创建时机
     */
    public static class CustomThreadFactory implements ThreadFactory {
        private static final AtomicInteger poolNumber = new AtomicInteger(1);
        private final ThreadGroup group;
        private final AtomicInteger threadNumber = new AtomicInteger(1);
        private final String namePrefix;

        CustomThreadFactory() {
            SecurityManager s = System.getSecurityManager();
            group = (s != null) ? s.getThreadGroup() :
                    Thread.currentThread().getThreadGroup();
            namePrefix = "pool-" +
                    poolNumber.getAndIncrement() +
                    "-thread-";
        }

        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r,
                    namePrefix + threadNumber.getAndIncrement(),
                    0);

            log.info("creating thread, thread name :{}", t.getName());
            if (t.isDaemon())
                t.setDaemon(false);
            if (t.getPriority() != Thread.NORM_PRIORITY)
                t.setPriority(Thread.NORM_PRIORITY);
            return t;
        }
    }

    /**
     * 自定义任务队列，来监听任务的入队时机
     * @param <E>
     */
    public static class CustomQueue<E> extends ArrayBlockingQueue<E> {
        CustomQueue(int capacity) {
            super(capacity);
        }

        @Override
        public boolean offer(E e) {
            boolean res = super.offer(e);
            if (res) {
                log.info("add task to queue, task count:{}", super.size());
            }
            return res;
        }
    }
}

上述代码执行日志

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------ tip: 此处新建的线程池，线程数未达到核心线程数，提交的任务都通过新建线程来处理
17:01:16.617 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-1
17:01:16.691 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-2
17:01:16.754 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-3
17:01:16.818 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-4
17:01:16.882 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-5
------ tip: 此处到达线程数量到达核心线程数，开始将任务添加到任务队列中
17:01:16.946 [main] INFO com.path.ExecutorConfiguration - add task to queue, task count:1
17:01:17.009 [main] INFO com.path.ExecutorConfiguration - add task to queue, task count:2
17:01:17.073 [main] INFO com.path.ExecutorConfiguration - add task to queue, task count:3
17:01:17.136 [main] INFO com.path.ExecutorConfiguration - add task to queue, task count:4
17:01:17.199 [main] INFO com.path.ExecutorConfiguration - add task to queue, task count:5
------ tip: 此处任务队列满了，开始新建线程来处理新增的任务
17:01:17.263 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-6
17:01:17.324 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-7
17:01:17.388 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-8
17:01:17.452 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-9
17:01:17.516 [main] INFO com.path.ExecutorConfiguration - creating thread, thread name :pool-1-thread-10
------ tip: 此处任务队列满了以及总线程达到最大线程数，则触发拒绝策略
17:01:17.578 [main] ERROR com.path.ExecutorConfiguration - thread pool reject task, task id :16
------ tip: 第1~5个任务已经由最开始新建的5个线程相继处理完成
17:01:17.626 [pool-1-thread-1] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-1 , handler task id: 1
17:01:17.705 [pool-1-thread-2] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-2 , handler task id: 2
17:01:17.768 [pool-1-thread-3] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-3 , handler task id: 3
17:01:17.832 [pool-1-thread-4] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-4 , handler task id: 4
17:01:17.894 [pool-1-thread-5] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-5 , handler task id: 5
------ tip: 第6~10个任务由于添加到任务队列，所以创建的第6~10个线程是处理第11~15个任务
17:01:18.275 [pool-1-thread-6] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-6 , handler task id: 11
17:01:18.339 [pool-1-thread-7] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-7 , handler task id: 12
17:01:18.403 [pool-1-thread-8] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-8 , handler task id: 13
17:01:18.466 [pool-1-thread-9] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-9 , handler task id: 14
17:01:18.528 [pool-1-thread-10] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-10 , handler task id: 15
------ tip: 第1~5个创建的线程在处理完第1~5个任务后，开始去任务队列获取第6~10个任务来处理
17:01:18.639 [pool-1-thread-1] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-1 , handler task id: 6
17:01:18.718 [pool-1-thread-2] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-2 , handler task id: 7
17:01:18.781 [pool-1-thread-3] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-3 , handler task id: 8
17:01:18.844 [pool-1-thread-4] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-4 , handler task id: 9
17:01:18.908 [pool-1-thread-5] INFO com.path.ExecutorConfiguration - thread name :pool-1-thread-5 , handler task id: 10
2025-06-07 该篇文章被 Nideil 打上标签: java 线程池

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