Spring中@Async注解执行异步任务的方法

Spring中@Async注解执行异步任务的方法

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：

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:context="http://springframework.org/schema/context"

xmlns:task="http://springframework.org/schema/task"

xsi:schemaLocation="http://springframework.org/schema/beans

http://springframework.org/schema/beans/spring-beans-4.0.xsd

http://springframework.org/schema/context

http://springframework.org/schema/context/spring-context.xsd

http://springframework.org/schema/task

http://springframework.org/schema/task/spring-task.xsd">

xmlns:xsi="http://w3.org/2001/XMLSchema-instance"

xmlns:context="http://springframework.org/schema/context"

xmlns:task="http://springframework.org/schema/task"

xsi:schemaLocation="http://springframework.org/schema/beans

http://springframework.org/schema/beans/spring-beans-4.0.xsd

http://springframework.org/schema/context

http://springframework.org/schema/context/spring-context.xsd

http://springframework.org/schema/task

http://springframework.org/schema/task/spring-task.xsd">

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 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 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.DefaultTestContextBootsLvKruZzaFRtrapper: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.TaskExecutorFactoLvKruZzaFRryBean] 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！

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