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

异步方法使用static修饰
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@Slf4jpublic 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;    }    @Async    public 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;    }    @Autowired    private FirstAsyncService fisrtService;    @Autowired    private SecondAsyncService secondService;
    public CompletableFuture<String> asyncMergeServicesResponse() throws InterruptedException {        CompletableFuture<String> fisrtServiceResponse = fisrtService.asyncGetData();        CompletableFuture<String> secondServiceResponse = secondService.asyncGetData();
        // Merge responses from FirstAsyncService and SecondAsyncService        return 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@Slf4jpublic class FirstAsyncService {    @Async    public 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@Slf4jpublic class SecondAsyncService {    @Async    public 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@EnableAsyncpublic class SpringAsyncConfig implements AsyncConfigurer {
    @Bean(name = "threadPoolTaskExecutor")    public Executor threadPoolTaskExecutor() {        return new ThreadPoolTaskExecutor();    }
    @Override    public Executor getAsyncExecutor() {        ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();        threadPoolTaskExecutor.initialize();        return threadPoolTaskExecutor;    }
    @Override    public 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 CustomAsyncExceptionHandler  implements AsyncUncaughtExceptionHandler {
    @Override    public 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

https://github.com/Harries/springboot-demo

3.测试

测试async异步任务

@Testpublic 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

@Testpublic 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

@Testpublic 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

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

4.引用参考

https://www.baeldung.com/spring-async
http://www.liuhaihua.cn/archives/710528.html
https://www.cnblogs.com/mingshan/p/17793507.html

ITPub博客

Spring Boot集成@Async快速入门Demo