問(wèn)題描述

springboot項(xiàng)目中，需要使用到異步調(diào)用某個(gè)方法，此時(shí) 第一個(gè)想到的就是 @Async 注解，但是 發(fā)現(xiàn) 方法執(zhí)行報(bào)錯(cuò)了，具體報(bào)錯(cuò)如下：

java.lang.NullPointerExceptionat com.ruoyi.common.utils.ServletUtils.getRequest(ServletUtils.java:56)at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:782)at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:717)at org.springframework.web.client.RestTemplate.postForObject(RestTemplate.java:443)at com.ruoyi.web.ecs.service.impl.EcsCollectOperateServiceImpl.collect(EcsCollectOperateServiceImpl.java:42)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:90)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:55)at java.lang.reflect.Method.invoke(Method.java:508)at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344)at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)at org.springframework.aop.interceptor.AsyncExecutionInterceptor.lambda$invoke$0(AsyncExecutionInterceptor.java:115)at java.util.concurrent.FutureTask.run(FutureTask.java:277)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1160)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)at java.lang.Thread.run(Thread.java:825)

上面日志有點(diǎn)多，其實(shí)核心就是這一部分日志：

java.lang.NullPointerExceptionat com.ruoyi.common.utils.ServletUtils.getRequest(ServletUtils.java:56)

這塊邏輯就是，使用spring底層提供的獲取上下文信息的方法。
所以說(shuō)明 獲取不到上下文信息，結(jié)果導(dǎo)致報(bào)錯(cuò)

解決辦法

• 對(duì)自定義的配置類(lèi) 進(jìn)行改造，原來(lái)的配置類(lèi)是這樣的：

import java.lang.reflect.Method;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;@Configuration
@EnableAsync
public class AsyncConfiguration {private static final Logger logger = LoggerFactory.getLogger(AsyncConfiguration.class);@Bean(name = "taskExecutor")public Executor getAsyncExecutor() {ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();// 核心線程數(shù)：線程池創(chuàng)建時(shí)候初始化的線程數(shù)taskExecutor.setCorePoolSize(10);// 最大線程數(shù)：線程池最大的線程數(shù)，只有在緩沖隊(duì)列滿了之后才會(huì)申請(qǐng)超過(guò)核心線程數(shù)的線程taskExecutor.setMaxPoolSize(20);// 緩沖隊(duì)列：用來(lái)緩沖執(zhí)行任務(wù)的隊(duì)列taskExecutor.setQueueCapacity(50);// 允許線程的空閑時(shí)間60秒：當(dāng)超過(guò)了核心線程之外的線程在空閑時(shí)間到達(dá)之后會(huì)被銷(xiāo)毀taskExecutor.setKeepAliveSeconds(60);// 線程池名的前綴：設(shè)置好了之后可以方便我們定位處理任務(wù)所在的線程池taskExecutor.setThreadNamePrefix("HiTask-");// 緩沖隊(duì)列滿了之后的拒絕策略：由調(diào)用線程處理（一般是主線程）//taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());taskExecutor.initialize();return taskExecutor;}class MyAsyncExceptionHandler implements AsyncUncaughtExceptionHandler {@Overridepublic void handleUncaughtException(Throwable throwable, Method method, Object... objects) {logger.error("MethodName={},Throwable={}",method.getName(),throwable.toString());}}
}

• 改造之后：

import java.lang.reflect.Method;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadPoolExecutor;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;@Configuration
@EnableAsync
public class AsyncConfiguration {private static final Logger logger = LoggerFactory.getLogger(AsyncConfiguration.class);@Bean(name = "taskExecutor")public Executor getAsyncExecutor() {ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();// 核心線程數(shù)：線程池創(chuàng)建時(shí)候初始化的線程數(shù)taskExecutor.setCorePoolSize(10);// 最大線程數(shù)：線程池最大的線程數(shù)，只有在緩沖隊(duì)列滿了之后才會(huì)申請(qǐng)超過(guò)核心線程數(shù)的線程taskExecutor.setMaxPoolSize(20);// 緩沖隊(duì)列：用來(lái)緩沖執(zhí)行任務(wù)的隊(duì)列taskExecutor.setQueueCapacity(50);// 允許線程的空閑時(shí)間60秒：當(dāng)超過(guò)了核心線程之外的線程在空閑時(shí)間到達(dá)之后會(huì)被銷(xiāo)毀taskExecutor.setKeepAliveSeconds(60);// 線程池名的前綴：設(shè)置好了之后可以方便我們定位處理任務(wù)所在的線程池taskExecutor.setThreadNamePrefix("HiTask-");// 緩沖隊(duì)列滿了之后的拒絕策略：由調(diào)用線程處理（一般是主線程）//taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());taskExecutor.initialize();//解決使用@Async注解，獲取不到上下文信息的問(wèn)題taskExecutor.setTaskDecorator(runnable -> {RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();return ()->{try {// 我們set 進(jìn)去 ,其實(shí)是一個(gè)ThreadLocal維護(hù)的.RequestContextHolder.setRequestAttributes(requestAttributes);runnable.run();} finally {// 最后記得釋放內(nèi)存RequestContextHolder.resetRequestAttributes();}};});return taskExecutor;}class MyAsyncExceptionHandler implements AsyncUncaughtExceptionHandler {@Overridepublic void handleUncaughtException(Throwable throwable, Method method, Object... objects) {logger.error("MethodName={},Throwable={}",method.getName(),throwable.toString());}}
}

總結(jié)

解決使用@Async注解，獲取不到上下文信息的問(wèn)題，只需要增加這一段代碼即可

 taskExecutor.setTaskDecorator(runnable -> {RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();return ()->{try {// 我們set 進(jìn)去 ,其實(shí)是一個(gè)ThreadLocal維護(hù)的.RequestContextHolder.setRequestAttributes(requestAttributes);runnable.run();} finally {// 最后記得釋放內(nèi)存RequestContextHolder.resetRequestAttributes();}};});

額外補(bǔ)充一點(diǎn)

如果使用 @Async注解，發(fā)現(xiàn)沒(méi)有生效，那有可能 你沒(méi)有加 @EnableAsync 注解。
@EnableAsync注解表示 開(kāi)啟異步任務(wù)，可以寫(xiě)在springboot的啟動(dòng)類(lèi)上，也可以寫(xiě)在 配置類(lèi)上