spring boot开启异步导致RequestContextHolder.currentRequestAttributes()为NULL_requestcontextholder.currentrequestattributes() 获取

现象

@Slf4j
public class MartinOAuth2FeignRequestInterceptor implements RequestInterceptor {
	。。。
    @Override
    public void apply(RequestTemplate requestTemplate) {
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.currentRequestAttributes();
        HttpServletRequest request = attributes.getRequest();
	。。。
    }
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在使用feign的RequestInterceptor 在服务间传递参数时，RequestContextHolder.currentRequestAttributes()报空指针异常

java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.
	at org.springframework.web.context.request.RequestContextHolder.currentRequestAttributes(RequestContextHolder.java:131)
	at com.java2e.martin.common.security.interceptor.MartinOAuth2FeignRequestInterceptor.apply(MartinOAuth2FeignRequestInterceptor.java:27)
	at feign.SynchronousMethodHandler.targetRequest(SynchronousMethodHandler.java:169)
	at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:99)
	at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:78)
	at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103)
	at com.sun.proxy.$Proxy185.addSystemLog(Unknown Source)
	at com.java2e.martin.common.log.event.LogListener.saveLog(LogListener.java:31)
	at com.java2e.martin.common.log.event.LogListener$$FastClassBySpringCGLIB$$5172b67e.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:749)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
	at org.springframework.aop.interceptor.AsyncExecutionInterceptor.lambda$invoke$0(AsyncExecutionInterceptor.java:115)
	at java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:266)
	at java.util.concurrent.FutureTask.run(FutureTask.java)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
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原因

RequestContextHolder将当前线程中的request信息存储在ThreadLocal中，开启另外一个线程异步调用feign，httpRequest是绑定在ThreadLocal中的，只能在当前线程中共享,子线程是不能获取到父线程的属性。

解决方案

1、取消异步调用，改为同步调用，如果用的注解，去掉 @Async即可

2、沿用异步调用，但是在调用前，把父线程request信息绑定给子线程，在方法执行的前面，加入以下语句

RequestContextHolder.setRequestAttributes(RequestContextHolder.getRequestAttributes(), true);
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后记

第二个方案应该也能修复 hystrix 使用线程池导致的RequestContextHolder.currentRequestAttributes()为NULL