Spring的多线程

一 点睛

Spring通过任务执行器（TaskExecutor）来实现多线程和并发编程。

使用ThreadPoolTaskExecutor可实现一个基于线程池的TaskExecutor。

实际开发中一般是非阻塞的，即异步的，所以我们要在配置类中通过@EnableAsync开启对异步任务的支持，并通过在实际执行的Bean的方法中使用@Async注解来声明其是一个异步任务。

二 ThreadPoolTaskExecutor类的核心属性

@SuppressWarnings("serial")
public class ThreadPoolTaskExecutor extends ExecutorConfigurationSupport
          implements AsyncListenableTaskExecutor, SchedulingTaskExecutor {
     private final Object poolSizeMonitor = new Object();
     private int corePoolSize = 1;
     private int maxPoolSize = Integer.MAX_VALUE;
     private int keepAliveSeconds = 60;
     private int queueCapacity = Integer.MAX_VALUE;
     private boolean allowCoreThreadTimeOut = false;
     private ThreadPoolExecutor threadPoolExecutor;
     ......
}

三 实战

1 配置类

package com.wisely.highlight_spring4.ch3.taskexecutor;

import java.util.concurrent.Executor;

import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.AsyncConfigurer;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
@Configuration
@ComponentScan("com.wisely.highlight_spring4.ch3.taskexecutor")
@EnableAsync //开启异步任务支持
//配置类实现AsyncConfigurer接口并重写getAsyncExecutor方法
public class TaskExecutorConfig implements AsyncConfigurer{

    //返回一个ThreadPoolTaskExecutor，这就就获得了一个基于线程池的TaskExecutor
    @Override
    public Executor getAsyncExecutor() {
         ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
            taskExecutor.setCorePoolSize(5);
            taskExecutor.setMaxPoolSize(10);
            taskExecutor.setQueueCapacity(25);
            taskExecutor.initialize();
            return taskExecutor;
    }

    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return null;
    }

}

2 任务执行类

package com.wisely.highlight_spring4.ch3.taskexecutor;

import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
@Service
public class AsyncTaskService {
    //表明该方法是异步方法，如果注解在类上，则表明该类的所有方法都是异步方法，
    //这里的方法自动被注入使用ThreadPoolTaskExecutor作为TaskExecutor
    @Async 
    public void executeAsyncTask(Integer i){
        System.out.println("执行异步任务: "+i);
    }

    @Async
    public void executeAsyncTaskPlus(Integer i){
        System.out.println("执行异步任务+1: "+(i+1));
    }

}

3 主类

package com.wisely.highlight_spring4.ch3.taskexecutor;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class Main {
     
     public static void main(String[] args) {
           AnnotationConfigApplicationContext context =
                     new AnnotationConfigApplicationContext(TaskExecutorConfig.class);
          
           AsyncTaskService asyncTaskService = context.getBean(AsyncTaskService.class);
          
           for(int i =0 ;i<10;i++){
               asyncTaskService.executeAsyncTask(i);
               asyncTaskService.executeAsyncTaskPlus(i);
             }
             context.close();
     }
}

四 运行结果——结果是并发执行而不是顺序执行

执行异步任务: 2

执行异步任务+1: 2

执行异步任务: 1

执行异步任务+1: 1

执行异步任务: 0

执行异步任务: 4

执行异步任务+1: 4

执行异步任务: 3

执行异步任务+1: 3

执行异步任务: 6

执行异步任务+1: 6

执行异步任务: 5

执行异步任务+1: 5

执行异步任务+1: 9

执行异步任务: 8

执行异步任务+1: 8

执行异步任务: 7

执行异步任务+1: 7

执行异步任务+1: 10

执行异步任务: 9

五 参考

https://blog.csdn.net/z55887/article/details/79060070

https://blog.csdn.net/fuyuwei2015/article/details/72758179