Spring MVC 追踪HandlerMapping

第一步:web.xml鼠标指向HandlerMapping右键+Ctrl进入它的类

第二步:Ctrl+F查找doDispatch()方法:

//入参个request
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HttpServletRequest processedRequest = request;
//处理器执行链
        HandlerExecutionChain mappedHandler = null;
//  多部分请求解析器
        boolean multipartRequestParsed = false;
        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

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

            try {
//指的是 DispatcherServlet 的实例  看看请求是不是多部分请求 
                processedRequest = this.checkMultipart(request);
                multipartRequestParsed = processedRequest != request;
                mappedHandler = this.getHandler(processedRequest);
                if (mappedHandler == null || mappedHandler.getHandler() == null) {
                    this.noHandlerFound(processedRequest, response);
                    return;
                }

                HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
                String method = request.getMethod();
                boolean isGet = "GET".equals(method);
                if (isGet || "HEAD".equals(method)) {
                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
                    if (this.logger.isDebugEnabled()) {
                        this.logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
                    }

                    if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {
                        return;
                    }
                }

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

                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
                if (asyncManager.isConcurrentHandlingStarted()) {
                    return;
                }

                this.applyDefaultViewName(processedRequest, mv);
                mappedHandler.applyPostHandle(processedRequest, response, mv);
            } catch (Exception var19) {
                dispatchException = var19;
            }

            this.processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
        } catch (Exception var20) {
            this.triggerAfterCompletion(processedRequest, response, mappedHandler, var20);
        } catch (Error var21) {
            this.triggerAfterCompletionWithError(processedRequest, response, mappedHandler, var21);
        } finally {
            if (asyncManager.isConcurrentHandlingStarted()) {
                if (mappedHandler != null) {
                    mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
                }
            } else if (multipartRequestParsed) {
                this.cleanupMultipart(processedRequest);
            }

        }

    }

第三步:找到了 mappedHandler  Ctrl+右键 进入getHandler

public interface HandlerMapping {
    String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping";
    String BEST_MATCHING_PATTERN_ATTRIBUTE = HandlerMapping.class.getName() + ".bestMatchingPattern";
    String INTROSPECT_TYPE_LEVEL_MAPPING = HandlerMapping.class.getName() + ".introspectTypeLevelMapping";
    String URI_TEMPLATE_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".uriTemplateVariables";
    String MATRIX_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".matrixVariables";
    String PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE = HandlerMapping.class.getName() + ".producibleMediaTypes";

    HandlerExecutionChain getHandler(HttpServletRequest var1) throws Exception;
}

第四步:发现他是一个接口Alt+H找实现类

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {

        Object handler = this.getHandlerInternal(request);
        if(handler == null) {
            handler = this.getDefaultHandler();
        }

        if(handler == null) {
            return null;
        } else {
            if(handler instanceof String) {
                String handlerName = (String)handler;  //  /hello
                handler = this.getApplicationContext().getBean(handlerName);
            }

            return this.getHandlerExecutionChain(handler, request);
        }
    }