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：
<?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！
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。
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