Sub thread get request

The child thread gets Request

Link to the original text https://zhhll.icu/2020/javaweb/ problem /7. The child thread gets Request/

Sometimes during business processing, a new thread will be opened to handle situations that are not so important to the business and irrelevant to the returned results , However, when starting a new thread for processing, it is found that it cannot be accessed from RequestContextHolder Get the current request , Take it out is null

This is because RequestContextHolder The information in is stored in ThreadLocal Medium , and ThreadLocal The data in is searched by threads , Not stored by this thread , It's impossible to find

private static final ThreadLocal<RequestAttributes> requestAttributesHolder =
      new NamedThreadLocal<RequestAttributes>("Request attributes");

private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder =
      new NamedInheritableThreadLocal<RequestAttributes>("Request context");

But sometimes the sub thread just needs to get the current request ？

This is where you're going to have to put RequestAttributes Object is set to be shared by child threads , Before starting the child thread

//  The main thread gets the request information first 
RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
//  Set child thread sharing 
RequestContextHolder.setRequestAttributes(requestAttributes,true);

What is the principle ？

public static void setRequestAttributes(RequestAttributes attributes, boolean inheritable) {
    
   if (attributes == null) {
    
      resetRequestAttributes();
   }
   else {
    
      if (inheritable) {
      //  If true, Then store the information in inheritableRequestAttributesHolder in 
         inheritableRequestAttributesHolder.set(attributes);
         requestAttributesHolder.remove();
      }
      else {
    
         requestAttributesHolder.set(attributes);
         inheritableRequestAttributesHolder.remove();
      }
   }
}

You can see NamedInheritableThreadLocal Rewrote getMap Method

ThreadLocalMap getMap(Thread t) {
    
   return t.inheritableThreadLocals;
}