spring之线程池集成

一时失言乱红尘 2022-05-21 10:38 139阅读 0赞

# spring之线程池集成 #

spring的线程池技术使用的是ThreadPoolTaskExecutor,当我们点进ThreadPoolTaskExecutor这个类的时候,可以看见里面是对于JDK中的ThreadPoolExecutor的封装:

![70][]

可见,ThreadPoolExecutor是ThreadPoolTaskExecutor类的一个属性.而其他几个属性正好也是ThreadPoolTaskExecutor的几个重要参数:

CorePoolSize:                        线程池维护线程的最小数量,默认值为1.

MaxPoolSize:                         线程池维护线程的最大数量,默认值为2的32次方-1,即2147483647.

KeepAliveSeconds:                空闲线程的存活时间,默认值是60s.

QueueCapacity:                     队列的最大长度,默认值为2的32次方-1,即2147483647.

AllowCoreThreadTimeOut:    是否允许核心线程空闲退出,默认是false.

RejectedExecutionHandler:      拒绝策略.这是ExecutorConfigurationSupport类中的方法,他是ThreadPoolExecutor的父类.

拒绝策略有以下四种:

ThreadPoolExecutor.AbortPolicy:                丢弃任务并抛出RejectedExecutionException异常.(默认使用)

ThreadPoolExecutor.DiscardPolicy:             丢弃任务,但是不不抛出异常.

ThreadPoolExecutor.DiscardOldestPolicy:   丢弃队列最前面的任务,然后重新尝试执行.

ThreadPoolExecutor.CallerRunsPolicy:        有调用线程处理该任务.

下面直接上代码:

首先是异步任务类:

package com.yczuoxin.demo.config;
    
    import org.springframework.scheduling.annotation.Async;
    import org.springframework.stereotype.Component;
    
    @Component
    public class AsyncTask {
        /** 表示异步执行 */
        @Async
        public void executeAsyncTask(Integer i){
            System.out.println("执行异步任务: " + i);
        }
    
        /** 表示异步执行 */
        @Async
        public void specialExecuteAsyncTask(Integer i){
            System.out.println("执行特殊异步任务: " + i);
        }
    }

下面是配置类:

package com.yczuoxin.demo.config;
    
    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;
    
    import java.util.concurrent.Executor;
    import java.util.concurrent.ThreadPoolExecutor;
    
    @Configuration
    /** 开启异步支持 */
    @EnableAsync
    @ComponentScan("com.yczuoxin.demo.config")
    public class TaskExecutorConfig implements AsyncConfigurer {
    
        @Override
        public Executor getAsyncExecutor() {
            ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
            executor.setCorePoolSize(5);
            executor.setMaxPoolSize(10);
            executor.setQueueCapacity(25);
            executor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
            executor.initialize();
            return executor;
        }
    
        @Override
        public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
            return null;
        }
    }

最后是测试类:

package com.yczuoxin.demo.config;
    
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    
    public class TaskTest {
        public static void main(String[] args) {
    
            int count = 10;
    
            AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(TaskExecutorConfig.class);
            AsyncTask task = context.getBean(AsyncTask.class);
            for (int i = 0; i < count; i++) {
                task.executeAsyncTask(i);
                task.specialExecuteAsyncTask(i);
            }
    
            context.close();
        }
    }

测试结果如下图:

![70 1][]

首先可以看见执行的结果并不是有序的.在执行一遍结果又不相同.异步线程池创建成功.

[70]: /images/20220521/0fa48bc0f10c4a0dbdd74295217fcb89.png
[70 1]: /images/20220521/db1c7d12a8d34bb9bf60be37663b15e9.png