是否有可能一个人完成网站开发培训心得模板

问题描述

springboot项目中，需要使用到异步调用某个方法，此时 第一个想到的就是 @Async 注解，但是 发现 方法执行报错了，具体报错如下：

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)

上面日志有点多，其实核心就是这一部分日志：

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

这块逻辑就是，使用spring底层提供的获取上下文信息的方法。
所以说明 获取不到上下文信息，结果导致报错

解决办法

• 对自定义的配置类 进行改造，原来的配置类是这样的：

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();// 核心线程数：线程池创建时候初始化的线程数taskExecutor.setCorePoolSize(10);// 最大线程数：线程池最大的线程数，只有在缓冲队列满了之后才会申请超过核心线程数的线程taskExecutor.setMaxPoolSize(20);// 缓冲队列：用来缓冲执行任务的队列taskExecutor.setQueueCapacity(50);// 允许线程的空闲时间60秒：当超过了核心线程之外的线程在空闲时间到达之后会被销毁taskExecutor.setKeepAliveSeconds(60);// 线程池名的前缀：设置好了之后可以方便我们定位处理任务所在的线程池taskExecutor.setThreadNamePrefix("HiTask-");// 缓冲队列满了之后的拒绝策略：由调用线程处理（一般是主线程）//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();// 核心线程数：线程池创建时候初始化的线程数taskExecutor.setCorePoolSize(10);// 最大线程数：线程池最大的线程数，只有在缓冲队列满了之后才会申请超过核心线程数的线程taskExecutor.setMaxPoolSize(20);// 缓冲队列：用来缓冲执行任务的队列taskExecutor.setQueueCapacity(50);// 允许线程的空闲时间60秒：当超过了核心线程之外的线程在空闲时间到达之后会被销毁taskExecutor.setKeepAliveSeconds(60);// 线程池名的前缀：设置好了之后可以方便我们定位处理任务所在的线程池taskExecutor.setThreadNamePrefix("HiTask-");// 缓冲队列满了之后的拒绝策略：由调用线程处理（一般是主线程）//taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());taskExecutor.initialize();//解决使用@Async注解，获取不到上下文信息的问题taskExecutor.setTaskDecorator(runnable -> {RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();return ()->{try {// 我们set 进去 ,其实是一个ThreadLocal维护的.RequestContextHolder.setRequestAttributes(requestAttributes);runnable.run();} finally {// 最后记得释放内存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());}}
}

总结

解决使用@Async注解，获取不到上下文信息的问题，只需要增加这一段代码即可

 taskExecutor.setTaskDecorator(runnable -> {RequestAttributes requestAttributes = RequestContextHolder.currentRequestAttributes();return ()->{try {// 我们set 进去 ,其实是一个ThreadLocal维护的.RequestContextHolder.setRequestAttributes(requestAttributes);runnable.run();} finally {// 最后记得释放内存RequestContextHolder.resetRequestAttributes();}};});

额外补充一点

如果使用 @Async注解，发现没有生效，那有可能 你没有加 @EnableAsync 注解。
@EnableAsync注解表示 开启异步任务，可以写在springboot的启动类上，也可以写在 配置类上