1.什么是@Async？

当我们在使用SpringBoot进行开发的时候，可能会遇到一些执行异步任务的场景，如果每次执行这些异步任务都去新建一个异步线程来执行的话，那代码就太冗余了。幸好SpringBoot给我们提供了Async的注解，让我们能够很轻松地对这些异步任务进行执行。

失效条件

1. 异步方法使用static修饰
2. 调用方法和异步方法在同一个类中

2.代码工程

实验目标：验证@async异步任务

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><parent><artifactId>springboot-demo</artifactId><groupId>com.et</groupId><version>1.0-SNAPSHOT</version></parent><modelVersion>4.0.0</modelVersion><artifactId>async</artifactId><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-autoconfigure</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency></dependencies>
</project>

service

• thenApply : 处理上一阶段计算结果
• thenCompose: 整合两个计算结果

package com.et.async.service;import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Future;/*** @author liuhaihua* @version 1.0* @ClassName NotifyServiceimpl* @Description todo*/
@Service
@Slf4j
public class NotifyService {public void noAsync() {log.info("Execute method asynchronously. " + Thread.currentThread().getName());}@Async("threadPoolTaskExecutor")public void withAsync() {log.info("Execute method asynchronously. " + Thread.currentThread().getName());}@Async("threadPoolTaskExecutor")public void mockerror() {int ss=12/0;}@Asyncpublic Future<String> asyncMethodWithReturnType() {log.info("Execute method asynchronously - " + Thread.currentThread().getName());try {Thread.sleep(5000);return new AsyncResult<String>("hello world !!!!");} catch (InterruptedException e) {e.printStackTrace();}return null;}@Autowiredprivate FirstAsyncService fisrtService;@Autowiredprivate SecondAsyncService secondService;public CompletableFuture<String> asyncMergeServicesResponse() throws InterruptedException {CompletableFuture<String> fisrtServiceResponse = fisrtService.asyncGetData();CompletableFuture<String> secondServiceResponse = secondService.asyncGetData();// Merge responses from FirstAsyncService and SecondAsyncServicereturn fisrtServiceResponse.thenCompose(fisrtServiceValue -> secondServiceResponse.thenApply(secondServiceValue -> fisrtServiceValue + secondServiceValue));}
}

package com.et.async.service;import lombok.extern.slf4j.Slf4j;
import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Service;import java.util.concurrent.CompletableFuture;/*** @author liuhaihua* @version 1.0* @ClassName FirstAsyncService* @Description todo* @date 2024年05月10日 16:24*/
@Service
@Slf4j
public class FirstAsyncService {@Asyncpublic CompletableFuture<String> asyncGetData() throws InterruptedException {log.info("Execute method asynchronously " + Thread.currentThread().getName());Thread.sleep(4000);return new AsyncResult<>(super.getClass().getSimpleName() + " response !!! ").completable();}
}

package com.et.async.service;import lombok.extern.slf4j.Slf4j;
import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Service;import java.util.concurrent.CompletableFuture;/*** @author liuhaihua* @version 1.0* @ClassName SecondAsyncService* @Description todo* @date 2024年05月10日 16:24*/
@Service
@Slf4j
public class SecondAsyncService {@Asyncpublic CompletableFuture<String> asyncGetData() throws InterruptedException {log.info("Execute method asynchronously " + Thread.currentThread().getName());Thread.sleep(4000);return new AsyncResult<>(super.getClass().getSimpleName() + " response !!! ").completable();}
}

config

一个@EnableAsync 注解启用

package com.et.async.config;import com.et.async.exception.CustomAsyncExceptionHandler;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Bean;
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;@Configuration
@EnableAsync
public class SpringAsyncConfig implements AsyncConfigurer {@Bean(name = "threadPoolTaskExecutor")public Executor threadPoolTaskExecutor() {return new ThreadPoolTaskExecutor();}@Overridepublic Executor getAsyncExecutor() {ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();threadPoolTaskExecutor.initialize();return threadPoolTaskExecutor;}@Overridepublic AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {return new CustomAsyncExceptionHandler();}
}

异常类

对于无返回值的异步任务，配置CustomAsyncExceptionHandler类，统一处理无法捕获的异常

package com.et.async.exception;import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;import java.lang.reflect.Method;public class CustomAsyncExceptionHandlerimplements AsyncUncaughtExceptionHandler {@Overridepublic void handleUncaughtException(Throwable throwable, Method method, Object... obj) {System.out.println("Exception message - " + throwable.getMessage());System.out.println("Method name - " + method.getName());for (Object param : obj) {System.out.println("Parameter value - " + param);}}}

以上只是一些关键代码，所有代码请参见下面代码仓库

代码仓库

• GitHub - Harries/springboot-demo: a simple springboot demo with some components for example: redis,solr,rockmq and so on.

3.测试

测试async异步任务

@Test
public void execute() throws ExecutionException, InterruptedException {log.info("your method test Code");log.info("Invoking an asynchronous method. " + Thread.currentThread().getName());notifyService.noAsync();notifyService.withAsync();}

测试带线程池的异步任务

@Async("threadPoolTaskExecutor")
public void mockerror() {int ss=12/0;
}

测试带返回值的异步方法

@Test
public void testAsyncAnnotationForMethodsWithReturnType()throws InterruptedException, ExecutionException {log.info("Invoking an asynchronous method. " + Thread.currentThread().getName());Future<String> future = notifyService.asyncMethodWithReturnType();while (true) {if (future.isDone()) {log.info("Result from asynchronous process - " + future.get());break;}log.info("Continue doing something else. ");Thread.sleep(1000);}
}

测试多个异步任务合并结果

@Test
public void testAsyncAnnotationForMergedServicesResponse() throws InterruptedException, ExecutionException {log.info("Invoking an asynchronous method. " + Thread.currentThread().getName());CompletableFuture<String> completableFuture = notifyService.asyncMergeServicesResponse();while (true) {if (completableFuture.isDone()) {log.info("Result from asynchronous process - " + completableFuture.get());break;}log.info("Continue doing something else. ");Thread.sleep(1000);}
}

测试void方法异常捕获

@Test
public void mockerror() throws ExecutionException, InterruptedException {notifyService.mockerror();
}

4.引用参考

• How To Do @Async in Spring | Baeldung
• Spring Boot集成@Async快速入门Demo | Harries Blog™
• https://www.cnblogs.com/mingshan/p/17793507.html