Springboot项目：解决@Async注解获取不到上下文信息问题

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.NullPointerException
	at 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.NullPointerException
	at 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 {

		@Override
		public 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 {

		@Override
		public 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