Spring中@Async注解执行异步任务
https://segmentfault.com/a/1190000015190901
引言
在业务处理中，有些业务使用异步的方式更为合理。比如在某个业务逻辑中，把一些数据存入到redis缓存中，缓存只是一个辅助的功能，成功或者失败对主业务并不会产生根本影响，这个过程可以通过异步的方法去进行。
Spring中通过在方法上设置@Async注解，可使得方法被异步调用。也就是说该方法会在调用时立即返回，而这个方法的实际执行交给Spring的TaskExecutor去完成。
代码示例
项目是一个普通的Spring的项目，Spring的配置文件：
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:task="http://www.springframework.org/schema/task"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/task
http://www.springframework.org/schema/task/spring-task.xsd">
<!-- 包扫描 -->
<context:component-scan base-package="com.lzumetal.ssm"/>
<!-- 执行异步任务的线程池TaskExecutor -->
<task:executor id="myexecutor" pool-size="5" />
<task:annotation-driven executor="myexecutor"/>
</beans>两个Service类：
package com.lzumetal.ssm.anotation.service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
/**
* 业务Service
*/
@Service
public class BusinessService {
private static final Logger log = LoggerFactory.getLogger(BusinessService.class);
@Autowired
private CacheService cacheService;
public void doBusiness() {
log.error("start to deal with our business");
cacheService.cacheData();
log.error("comlete service operation");
}
/**
* 获取异步方法执行的返回值
*/
public void doBusinessWithAsyncReturn() throws ExecutionException, InterruptedException {
log.error("start to deal with our business");
Future<String> future = cacheService.cacheDataWithReturn();
log.error(future.get()); //future.get()方法是会阻塞的
log.error("comlete service operation");
}
}package com.lzumetal.ssm.anotation.service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.stereotype.Service;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
/**
* 缓存服务
*/
@Service
public class CacheService {
private static final Logger log = LoggerFactory.getLogger(CacheService.class);
@Async(value = "myexecutor") //指定执行任务的TaskExecutor
public void cacheData() {
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.error("success store the result to cache");
}
@Async
public Future<String> cacheDataWithReturn() {
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.error("success store the result to cache");
//返回的结果需要通过AsyncResult这个类包装
return new AsyncResult<>("Async operation success");
}
}
测试类：
package com.lzumetal.ssm.anotation.test;
import com.lzumetal.ssm.anotation.service.BusinessService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import java.util.concurrent.TimeUnit;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {"classpath:spring-context.xml"})
public class MainTest {
@Autowired
private BusinessService businessService;
@Test
public void test() throws InterruptedException {
businessService.doBusiness();
//不让主线程过早结束，否则控制台看不到异步方法中的输出内容
TimeUnit.SECONDS.sleep(5L);
}
@Test
public void testAsyncReturn() throws Exception {
businessService.doBusinessWithAsyncReturn();
TimeUnit.SECONDS.sleep(5L);
}
}执行test()方法的结果：
22:20:33,207 INFO main support.DefaultTestContextBootstrapper:260 - Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
22:20:33,226 INFO main support.DefaultTestContextBootstrapper:209 - Could not instantiate TestExecutionListener [org.springframework.test.context.web.ServletTestExecutionListener]. Specify custom listener classes or make the default listener classes (and their required dependencies) available. Offending class: [javax/servlet/ServletContext]
22:20:33,227 INFO main support.DefaultTestContextBootstrapper:187 - Using TestExecutionListeners: [org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@100fc185, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@643b1d11, org.springframework.test.context.support.DirtiesContextTestExecutionListener@2ef5e5e3, org.springframework.test.context.transaction.TransactionalTestExecutionListener@36d4b5c, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@6d00a15d]22:20:33,324 INFO main xml.XmlBeanDefinitionReader:317 - Loading XML bean definitions from class path resource [spring-context.xml]
22:20:33,585 INFO main support.GenericApplicationContext:583 - Refreshing org.springframework.context.support.GenericApplicationContext@4f7d0008: startup date [Wed May 30 22:20:33 CST 2018]; root of context hierarchy
22:20:33,763 INFO main concurrent.ThreadPoolTaskExecutor:165 - Initializing ExecutorService
22:20:33,766 INFO main support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker:325 - Bean 'myexecutor' of type [org.springframework.scheduling.config.TaskExecutorFactoryBean] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
22:20:33,767 INFO main support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker:325 - Bean 'myexecutor' of type [org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
22:20:34,107 ERROR main service.BusinessService:24 - start to deal with our business
22:20:34,113 ERROR main service.BusinessService:26 - comlete service operation
22:20:37,166 ERROR myexecutor-1 service.CacheService:28 - success store the result to cache
22:20:39,117 INFO Thread-0 support.GenericApplicationContext:984 - Closing org.springframework.context.support.GenericApplicationContext@4f7d0008: startup date [Wed May 30 22:20:33 CST 2018]; root of context hierarchy
22:20:39,118 INFO Thread-0 concurrent.ThreadPoolTaskExecutor:203 - Shutting down ExecutorService执行testAsyncReturn()方法的结果：
21:38:16,908 INFO main support.DefaultTestContextBootstrapper:260 - Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.test.context.web.ServletTestExecutionListener, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener, org.springframework.test.context.support.DependencyInjectionTestExecutionListener, org.springframework.test.context.support.DirtiesContextTestExecutionListener, org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
21:38:16,926 INFO main support.DefaultTestContextBootstrapper:209 - Could not instantiate TestExecutionListener [org.springframework.test.context.web.ServletTestExecutionListener]. Specify custom listener classes or make the default listener classes (and their required dependencies) available. Offending class: [javax/servlet/ServletContext]
21:38:16,927 INFO main support.DefaultTestContextBootstrapper:187 - Using TestExecutionListeners: [org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@100fc185, org.springframework.test.context.support.DependencyInjectionTestExecutionListener@643b1d11, org.springframework.test.context.support.DirtiesContextTestExecutionListener@2ef5e5e3, org.springframework.test.context.transaction.TransactionalTestExecutionListener@36d4b5c, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener@6d00a15d]21:38:17,025 INFO main xml.XmlBeanDefinitionReader:317 - Loading XML bean definitions from class path resource [spring-context.xml]
21:38:17,263 INFO main support.GenericApplicationContext:583 - Refreshing org.springframework.context.support.GenericApplicationContext@4f7d0008: startup date [Wed May 30 21:38:17 CST 2018]; root of context hierarchy
21:38:17,405 INFO main concurrent.ThreadPoolTaskExecutor:165 - Initializing ExecutorService
21:38:17,407 INFO main support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker:325 - Bean 'myexecutor' of type [org.springframework.scheduling.config.TaskExecutorFactoryBean] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
21:38:17,407 INFO main support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker:325 - Bean 'myexecutor' of type [org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
21:38:17,692 ERROR main service.BusinessService:35 - start to deal with our business
21:38:20,833 ERROR myexecutor-1 service.CacheService:39 - success store the result to cache
21:38:20,834 ERROR main service.BusinessService:37 - Async operation success
21:38:20,835 ERROR main service.BusinessService:38 - comlete service operation
21:38:25,838 INFO Thread-0 support.GenericApplicationContext:984 - Closing org.springframework.context.support.GenericApplicationContext@4f7d0008: startup date [Wed May 30 21:38:17 CST 2018]; root of context hierarchy
21:38:25,839 INFO Thread-0 concurrent.ThreadPoolTaskExecutor:203 - Shutting down ExecutorService@Async的使用注意点
- 返回值：不要返回值直接void；需要返回值用AsyncResult或者CompletableFuture
- 可自定义执行器并指定例如：@Async("otherExecutor")
@Async必须不同类间调用： A类—>B类.C方法()（@Async注释在B类/方法中），如果在同一个类中调用，会变同步执行,例如:A类.B()—>A类.@Async C()。- @Async也可以加到类，表示这个类的所有方法都是异步执行，并且方法上的注解会覆盖类上的注解。但一般不这么用！
___________________________________________________________________________________________________________________________________________________________
@Async Could not find unique TaskExecutor bean; NoUniqueBeanDefinitionException;
异步任务，项目启动或接口调用，控制台报错：Could not find unique TaskExecutor bean;
或者报错：org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'org.springframework.core.task.TaskExecutor' available: expected single matching bean but found 2: applicationTaskExecutor,taskScheduler
原因为：@Async所注解的方法存在相同的方法名，或者同一个异步任务被多个任务同时调用
解决方法：
1、将@Async所注解的方法名修改为不同的方法名
2、增加异步任务配置类：
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; /** * @description 异步任务配置类，为防止异步任务如下错误： * No qualifying bean of type 'org.springframework.core.task.TaskExecutor' available: * expected single matching bean but found 2: applicationTaskExecutor,taskScheduler * @author: chenping * @create: 2020-01-17 **/ @Configuration @ComponentScan("cn.com.*.*.*.service")//异步任务所在的包 @EnableAsync //开启异步任务支持 public class TaskExecutorConfig implements AsyncConfigurer { /** * @description: 实现AsyncConfigurer接口并重写getAsyncExecutor方法， * 并返回一个ThreadPoolTaskExecutor，这样我们就获得了一个基于线程池TaskExecutor * @param: * @return: java.util.concurrent.Executor * @author: chenping * @date: 2020/1/17 **/ @Override public Executor getAsyncExecutor() { ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor(); taskExecutor.setCorePoolSize(10); taskExecutor.setMaxPoolSize(80); taskExecutor.setQueueCapacity(100); taskExecutor.initialize(); return taskExecutor; } @Override public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() { return null; } }