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开发中多线程与并发编程是必不可少的,而Spring中也有相应的工具类来实现这一功能,使用ThreadPoolTaskExecutor可实现一个基于线程池的TaskExecutor。联系实际,一般开发中常用异步任务,因此需要在Spring中实现异步任务主要有两步:
1.在配置类中通过@EnableAsync开启对异步任务的支持。
2.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。
首先了解一下何为异步任务,异步是相对同步而言的,所谓同步就是任务一个个有序完成的,会出现阻塞情况;而异步则是执行一个任务,将任务在后台挂起,然后继续执行程序,等后台任务处理完毕后就返回结果,所以异步就是无阻塞、无序的。
本文将举一个例子进行比较两者的区别。
1.配置类
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;
/**
* 实现一个基于线程池的taskExecutor
*
*/
@Configuration
@ComponentScan("com.carson.taskdemo")
@EnableAsync
public class TaskExecutorConfig implements AsyncConfigurer {
public Executor getAsyncExecutor() {
ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
taskExecutor.setCorePoolSize(5);
taskExecutor.setMaxPoolSize(10);
taskExecutor.setQueueCapacity(20);
taskExecutor.initialize();
return taskExecutor;
}
public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
return null;
}
}
2.任务执行类
这里主要同步和异步的区别主要是@Async注解,该注解修饰类时,则表明该类的所有方法都是异步方法,修饰方法时表示该方法是异步方法。以下分别是同步和异步的代码:
同步:
package com.carson.taskdemo;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
@Service
public class AsyncTaskService {
//@Async
public void test1(Integer i){
System.out.println("执行任务:"+i);
}
//@Async
public void test2(Integer i){
System.out.println("执行任务+1:"+(i+1));
}
}
异步:
package com.carson.taskdemo;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
@Service
public class AsyncTaskService {
@Async
public void test1(Integer i){
System.out.println("执行任务:"+i);
}
@Async
public void test2(Integer i){
System.out.println("执行任务+1:"+(i+1));
}
}
3.运行类
package com.carson.taskdemo;
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.test1(i);
asyncTaskService.test2(i);
}
context.close();
}
}
运行结果如下:
同步:
一月 12, 2019 10:39:08 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@4437c4: startup date [Sat Jan 12 10:39:08 CST 2019]; root of context hierarchy
一月 12, 2019 10:39:08 上午 org.springframework.context.support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker postProcessAfterInitialization
信息: Bean 'taskExecutorConfig' of type [class com.carson.taskdemo.TaskExecutorConfig$$EnhancerBySpringCGLIB$$141c69f3] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
一月 12, 2019 10:39:08 上午 org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor initialize
信息: Initializing ExecutorService
一月 12, 2019 10:39:08 上午 org.springframework.context.support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker postProcessAfterInitialization
信息: Bean 'org.springframework.scheduling.annotation.ProxyAsyncConfiguration' of type [class org.springframework.scheduling.annotation.ProxyAsyncConfiguration$$EnhancerBySpringCGLIB$$150bf3d2] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
一月 12, 2019 10:39:08 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@4437c4: startup date [Sat Jan 12 10:39:08 CST 2019]; root of context hierarchy
执行任务:0
执行任务+1:1
执行任务:1
执行任务+1:2
执行任务:2
执行任务+1:3
执行任务:3
执行任务+1:4
执行任务:4
执行任务+1:5
执行任务:5
执行任务+1:6
执行任务:6
执行任务+1:7
执行任务:7
执行任务+1:8
执行任务:8
执行任务+1:9
执行任务:9
执行任务+1:10
Process finished with exit code 0
异步:
一月 12, 2019 10:37:31 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@4437c4: startup date [Sat Jan 12 10:37:31 CST 2019]; root of context hierarchy
一月 12, 2019 10:37:31 上午 org.springframework.context.support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker postProcessAfterInitialization
信息: Bean 'taskExecutorConfig' of type [class com.carson.taskdemo.TaskExecutorConfig$$EnhancerBySpringCGLIB$$fb152f6b] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
一月 12, 2019 10:37:31 上午 org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor initialize
信息: Initializing ExecutorService
一月 12, 2019 10:37:31 上午 org.springframework.context.support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker postProcessAfterInitialization
信息: Bean 'org.springframework.scheduling.annotation.ProxyAsyncConfiguration' of type [class org.springframework.scheduling.annotation.ProxyAsyncConfiguration$$EnhancerBySpringCGLIB$$fc04b94a] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
一月 12, 2019 10:37:31 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext doClose
信息: Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@4437c4: startup date [Sat Jan 12 10:37:31 CST 2019]; root of context hierarchy
执行任务:0
执行任务:2
执行任务+1:1
执行任务+1:3
执行任务+1:4
执行任务+1:5
执行任务+1:2
执行任务+1:6
执行任务:1
执行任务+1:7
执行任务:6
执行任务+1:8
执行任务:5
执行任务+1:9
执行任务:9
执行任务:4
执行任务:3
执行任务+1:10
执行任务:8
执行任务:7
比较两种结果可以看出同步的是有序的,而异步的则是并发执行的。