浅谈SpringMVC请求映射handler源码解读

@Bean
@Primary
@Override
public RequestMappingHandlerMapping requestMappingHandlerMapping(
  @Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager,
  @Qualifier("mvcConversionService") FormattingConversionService conversionService,
  @Qualifier("mvcResourceUrlProvider") ResourceUrlProvider resourceUrlProvider) {
  // Must be @Primary for MvcUriComponentsBuilder to work
  return super.requestMappingHandlerMapping(contentNegotiationManager, conversionService,
                       resourceUrlProvider);
}

@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,
                              FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
  WelcomePageHandlerMapping welcomePageHandlerMapping = new WelcomePageHandlerMapping(
    new TemplateAvailabilityProviders(applicationContext), applicationContext, getWelcomePage(),
    this.mvcProperties.getStaticPathPattern());
  welcomePageHandlerMapping.setInterceptors(getInterceptors(mvcConversionService, mvcResourceUrlProvider));
  welcomePageHandlerMapping.setCorsConfigurations(getCorsConfigurations());
  return welcomePageHandlerMapping;
}

@Override
protected void service(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException {

  HttpMethod httpMethod = HttpMethod.resolve(request.getMethod());
  if (httpMethod == HttpMethod.PATCH || httpMethod == null) {
    processRequest(request, response);
  }
  else {
    //父类根据method参数执行doGet,doPost,doDelete等
    super.service(request, response);
  }
}

@Overrideprotected 
final void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  //核心方法
  processRequest(request, response);
}

protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException {
  try {
  //进入此核心方法
  doService(request, response);
}
catch (ServletException | IOException ex) {
  failureCause = ex;
  throw ex;
}
catch (Throwable ex) {
  failureCause = ex;
  throw new NestedServletException("Request processing failed", ex);
}

finally {
  resetContextHolders(request, previousLocaleContext, previousAttributes);
  if (requestAttributes != null) {
    requestAttributes.requestCompleted();
  }
  logResult(request, response, failureCause, asyncManager);
  publishRequestHandledEvent(request, response, startTime, failureCause);
}

@Override
	protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
 ····

   try {
     //这里为实际分发控制器的逻辑，其内部是找到对应的handlerMapper
     doDispatch(request, response);
   }
    finally {
      if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
        // Restore the original attribute snapshot, in case of an include.
        if (attributesSnapshot != null) {
          restoreAttributesAfterInclude(request, attributesSnapshot);
        }
      }
      if (requestPath != null) {
        ServletRequestPathUtils.clearParsedRequestPath(request);
      }
    }
}

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.
      mappedHandler = getHandler(processedRequest);
      if (mappedHandler == null) {
        noHandlerFound(processedRequest, response);
        return;
      }

      // Determine handler adapter for the current request.
      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 (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
          return;
        }
      }

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

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

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

      applyDefaultViewName(processedRequest, mv);
      mappedHandler.applyPostHandle(processedRequest, response, mv);
    }
    catch (Exception ex) {
      dispatchException = ex;
    }
    catch (Throwable err) {
      // As of 4.3, we're processing Errors thrown from handler methods as well,
      // making them available for @ExceptionHandler methods and other scenarios.
      dispatchException = new NestedServletException("Handler dispatch failed", err);
    }
    processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
  }
  catch (Exception ex) {
    triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
  }
  catch (Throwable err) {
    triggerAfterCompletion(processedRequest, response, mappedHandler,
                new NestedServletException("Handler processing failed", err));
  }
  finally {
    if (asyncManager.isConcurrentHandlingStarted()) {
      // Instead of postHandle and afterCompletion
      if (mappedHandler != null) {
        mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
      }
    }
    else {
      // Clean up any resources used by a multipart request.
      if (multipartRequestParsed) {
        cleanupMultipart(processedRequest);
      }
    }
  }
}

protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
  if (this.handlerMappings != null) {
    for (HandlerMapping mapping : this.handlerMappings) {
      HandlerExecutionChain handler = mapping.getHandler(request);
      if (handler != null) {
        return handler;
      }
    }
  }
  return null;
}