SpringMVC中RequestContextHolder获取请求信息的方法

 ServletRequestAttributes attrs = (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
HttpServletRequest request = attrs.getRequest();

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

  public static void setRequestAttributes(@Nullable RequestAttributes attributes) {
    setRequestAttributes(attributes, false);
  }

  public static void setRequestAttributes(@Nullable RequestAttributes attributes, boolean inheritable) {
    if (attributes == null) {
      resetRequestAttributes();
    } else if (inheritable) {
      inheritableRequestAttributesHolder.set(attributes);
      requestAttributesHolder.remove();
    } else {
      requestAttributesHolder.set(attributes);
      inheritableRequestAttributesHolder.remove();
    }

  }

 private void initContextHolders(HttpServletRequest request, @Nullable LocaleContext localeContext, @Nullable RequestAttributes requestAttributes) {
    if (localeContext != null) {
      LocaleContextHolder.setLocaleContext(localeContext, this.threadContextInheritable);
    }

    if (requestAttributes != null) {
      RequestContextHolder.setRequestAttributes(requestAttributes, this.threadContextInheritable);
    }

    if (this.logger.isTraceEnabled()) {
      this.logger.trace("Bound request context to thread: " + request);
    }

  }

  @Nullable
  public static RequestAttributes getRequestAttributes() {
    RequestAttributes attributes = (RequestAttributes)requestAttributesHolder.get();
    if (attributes == null) {
      attributes = (RequestAttributes)inheritableRequestAttributesHolder.get();
    }

    return attributes;
  }

//得到存储进去的request
private static final ThreadLocal<RequestAttributes> requestAttributesHolder =
new NamedThreadLocal<RequestAttributes>("Request attributes");
//可被子线程继承的request
private static final ThreadLocal<RequestAttributes> inheritableRequestAttributesHolder =
new NamedInheritableThreadLocal<RequestAttributes>("Request context");

public static RequestAttributes getRequestAttributes() {
    RequestAttributes attributes = requestAttributesHolder.get();
    if (attributes == null) {
      attributes = inheritableRequestAttributesHolder.get();
    }
    return attributes;
  }

protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
long startTime = System.currentTimeMillis();
Throwable failureCause = null;
//获取上一个请求保存的LocaleContext
  LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();
//建立新的LocaleContext
  LocaleContext localeContext = buildLocaleContext(request);
//获取上一个请求保存的RequestAttributes
  RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
//建立新的RequestAttributes
  ServletRequestAttributes requestAttributes = buildRequestAttributes(request, 
response, previousAttributes);
  WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), 
new RequestBindingInterceptor());
//具体设置的方法
  initContextHolders(request, localeContext, requestAttributes);
try {
    doService(request, response);
  }
catch (ServletException ex) {
failureCause = ex;
throw ex;
  }
catch (IOException ex) {
  failureCause = ex;
  throw ex;
  }
catch (Throwable ex) {
  failureCause = ex;
  throw new NestedServletException("Request processing failed", ex);
  }
finally {
//恢复
    resetContextHolders(request, previousLocaleContext, previousAttributes);
if (requestAttributes != null) {
requestAttributes.requestCompleted();
    }
if (logger.isDebugEnabled()) {
if (failureCause != null) {
this.logger.debug("Could not complete request", failureCause);
      }
else {
if (asyncManager.isConcurrentHandlingStarted()) {
          logger.debug("Leaving response open for concurrent processing");
        }
else {
this.logger.debug("Successfully completed request");
        }
      }
    }
//发布事件
    publishRequestHandledEvent(request, response, startTime, failureCause);
  }
}

private void initContextHolders(HttpServletRequest request, 
                LocaleContext localeContext, 
                RequestAttributes requestAttributes) {
if (localeContext != null) {
    LocaleContextHolder.setLocaleContext(localeContext, 
this.threadContextInheritable);
  }
if (requestAttributes != null) {
    RequestContextHolder.setRequestAttributes(requestAttributes, 
this.threadContextInheritable);
  }
if (logger.isTraceEnabled()) {
    logger.trace("Bound request context to thread: " + request);
  }
}