解读SpringBoot中addCorsMappings配置跨域与拦截器互斥问题的原因

public WebMvcConfigurer corsConfigurer() {
        return new WebMvcConfigurerAdapter() {
            @Override
            public void addCorsMappings(CorsRegistry registry) {
                        registry.addMapping("/**")
                        .allowedOrigins(origins)
                        .allowedHeaders("*")
                        .allowCredentials(true)
                        .allowedMethods("*")
                        .maxAge(3600);
            }
        };
    }

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HttpServletRequest processedRequest = request;
		HandlerExecutionChain mappedHandler = null;
		boolean multipartRequestParsed = false;

		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

		try {
			ModelAndView mv = null;
			Exception dispatchException = null;

			try {
				processedRequest = checkMultipart(request);
				multipartRequestParsed = (processedRequest != request);

				// Determine handler for the current request. 
		（1）mappedHandler = getHandler(processedRequest);
				if (mappedHandler == null || mappedHandler.getHandler() == null) {
					noHandlerFound(processedRequest, response);
					return;
				}

				// Determine handler adapter for the current request.
		（2）HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

				// Process last-modified header, if supported by the handler.
				String method = request.getMethod();
				boolean isGet = "GET".equals(method);
				if (isGet || "HEAD".equals(method)) {
					long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
					if (logger.isDebugEnabled()) {
						logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
					}
					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
						return;
					}
				}

		（3）if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}

				// Actually invoke the handler.
		（4）mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

				if (asyncManager.isConcurrentHandlingStarted()) {
					return;
				}

				applyDefaultViewName(processedRequest, mv);
		（5）mappedHandler.applyPostHandle(processedRequest, response, mv);
			}

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
（1）Object handler = getHandlerInternal(request);
		if (handler == null) {
			handler = getDefaultHandler();
		}
		if (handler == null) {
			return null;
		}
		// Bean name or resolved handler?
		if (handler instanceof String) {
			String handlerName = (String) handler;
			handler = getApplicationContext().getBean(handlerName);
		}

（2）HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
		if (CorsUtils.isCorsRequest(request)) {
			CorsConfiguration globalConfig = this.globalCorsConfigSource.getCorsConfiguration(request);
			CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
			CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
（3）	executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
		}
		return executionChain;
	}

protected HandlerExecutionChain getCorsHandlerExecutionChain(HttpServletRequest request,
			HandlerExecutionChain chain, CorsConfiguration config) {

		if (CorsUtils.isPreFlightRequest(request)) {
			HandlerInterceptor[] interceptors = chain.getInterceptors();
			chain = new HandlerExecutionChain(new PreFlightHandler(config), interceptors);
		}
		else {
			chain.addInterceptor(new CorsInterceptor(config));
		}
		return chain;
	}