SpringBoot線程池的使用

第一步、配置線程池

package com.kyy.springboot.pool;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.ThreadPoolExecutor;

/**
 * Auth: zhouhongliang
 * Date：2019/8/1
 */
@Configuration
public class GlobalConfig {
    @Bean
    public ThreadPoolTaskExecutor defaultThreadPool(){
        ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
        //核心線程數量
        threadPoolTaskExecutor.setCorePoolSize(2);
        //最大線程數量
        threadPoolTaskExecutor.setMaxPoolSize(5);
        //隊列中最大任務數
        threadPoolTaskExecutor.setQueueCapacity(2);
        //線程名稱前綴
        threadPoolTaskExecutor.setThreadNamePrefix("ThreadPool-");
        //當達到最大線程數時如何處理新任務
        threadPoolTaskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        //線程空閒後最大存活時間
        threadPoolTaskExecutor.setKeepAliveSeconds(60);
        //初始化線程池
        threadPoolTaskExecutor.initialize();
        return threadPoolTaskExecutor;
    }
}

第二步、創建Service

package com.kyy.springboot.service;

import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

/**
 * Auth: zhouhongliang
 * Date：2019/8/1
 */
@Service
public class BootService {
    @Resource(name = "defaultThreadPool")
    private ThreadPoolTaskExecutor poolTaskExecutor;

    @Async
    public void testPool() {
        System.out.println("線程名稱：" + Thread.currentThread().getName());
    }

    public void testNoPool() {
        System.out.println("線程名稱：" + Thread.currentThread().getName());
    }

    public int testPoolTaskExecutor(int n) throws InterruptedException, ExecutionException {
        CountDownLatch countDownLatch = new CountDownLatch(n);
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        int sum = 0;
        for (int i = 1; i <= n; i++) {
            final int index = i;
            final Future<Integer> future = poolTaskExecutor.submit(() -> {
                Thread.sleep(5000);
                System.out.println(simpleDateFormat.format(new Date())+" "+Thread.currentThread().getName() + " 執行 " + index);
                countDownLatch.countDown();
                return 1;
            });
        }
        countDownLatch.await();
        return sum;
    }
}

第三步：創建Controller

package com.kyy.springboot.controller;

import com.kyy.springboot.service.BootService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.ExecutionException;

/**
 * Auth: zhouhongliang
 * Date：2019/8/1
 */
@RestController
public class PoolController {
    @Autowired
    private BootService bootService;
    @RequestMapping("/pool")
    public String pool(){
        for (int i=0;i<100;i++){
            bootService.testPool();
        }
        return "pool test";
    }
    @RequestMapping("/poolTask/{n}")
    public String poolTask(@PathVariable int n){
        long startTime = System.currentTimeMillis();
        try {
            bootService.testPoolTaskExecutor(n);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        long endTime = System.currentTimeMillis();
        return "poolTask test "+(endTime-startTime)/1000+" 秒";
    }
}

第四步：創建啓動類

package com.kyy.springboot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.scheduling.annotation.EnableAsync;

/**
 * 啓動程序
 * @Auther：zhouhongliang
 * @Date：2019/7/30
 * @Description：
 */
@SpringBootApplication
@EnableAsync
public class SpringBootDemo {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootDemo.class,args);
    }
}

總結：線程池配置說明
1、屬性字段說明

corePoolSize：線程池維護線程的最少數量

keepAliveSeconds：允許的空閒時間

maxPoolSize：線程池維護線程的最大數量

queueCapacity：緩存隊列

rejectedExecutionHandler：對拒絕task的處理策略

2、 execute(Runable)方法執行過程
如果此時線程池中的數量小於corePoolSize，即使線程池中的線程都處於空閒狀態，也要創建新的線程來處理被添加的任務。

如果此時線程池中的數量等於 corePoolSize，但是緩衝隊列 workQueue未滿，那麼任務被放入緩衝隊列。

如果此時線程池中的數量大於corePoolSize，緩衝隊列workQueue滿，並且線程池中的數量小於maxPoolSize，建新的線程來處理被添加的任務。

如果此時線程池中的數量大於corePoolSize，緩衝隊列workQueue滿，並且線程池中的數量等於maxPoolSize，那麼通過handler所指定的策略來處理此任務。也就是：處理任務的優先級爲：核心線程corePoolSize、任務隊列workQueue、最大線程 maximumPoolSize，如果三者都滿了，使用handler處理被拒絕的任務。

當線程池中的線程數量大於corePoolSize時，如果某線程空閒時間超過keepAliveTime，線程將被終止。這樣，線程池可以動態的調整池中的線程數。