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前言

從DispatchServlet可以看出整個SpringMVC流程，關(guān)于過濾器（filter），servelet，攔截器（interceptor）的執(zhí)行流程如下如

image-20211018153111255.png

使用到的組件

過濾器Filter：對請求信息進(jìn)行校驗，處理，例如判斷是否有token，或者向請求添加請求頭，請求參數(shù)等

新增filter的兩種方式：

@WebFilter(urlPatterns = "/*",filterName = "myFilter") // 指定filter的處理路徑和，filter名稱
@Component
public class MyFilter implements Filter {
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setAttribute("userId","zhangsan");
        MDC.put("traceId", IdUtil.simpleUUID());
        //log.error("過濾器doFilter---請求添加請求數(shù)據(jù)userId");
        filterChain.doFilter(servletRequest,servletResponse);
    }
}

@Bean
public FilterRegistrationBean<MyFilter> myFilter(){
    final FilterRegistrationBean<MyFilter> registrationBean = new FilterRegistrationBean<>();
    final MyFilter myFilter = new MyFilter();
    registrationBean.setFilter(myFilter);
    registrationBean.setUrlPatterns(Arrays.asList("/*"));
    registrationBean.setName("myFilter");
    return registrationBean;
}

servlet：serlvet是處理請求的入口，DispatchServlet繼承自Servlet，所有的請求都會走DispatchServlet，并且內(nèi)部添加了對Rest風(fēng)格的請求處理邏輯

添加普通servlet的兩種方式

@WebServlet(urlPatterns = "/*",name = "myServlet")
@Component
public class MyServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }

    @Override
    protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doDelete(req, resp);
    }
}

@Bean
public ServletRegistrationBean<MyServlet> myServlet(){
    final ServletRegistrationBean<MyServlet> registrationBean = new ServletRegistrationBean<>();
    final MyServlet myServlet = new MyServlet();
    registrationBean.setServlet(myServlet);
    registrationBean.setUrlMappings(Arrays.asList("/*"));
    registrationBean.setName("myServlet");
    return registrationBean;
}

自定義DIspatchServlet：

@Component("dispatcherServlet")
public class MyDispatcherServlet extends DispatcherServlet {
    @Override
    protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
        log.error("請求調(diào)用----："+request.getRequestURL());
        super.doService(request, response);
    }
}

攔截器interceptor：在方法執(zhí)行前后，結(jié)束時進(jìn)行處理

新增攔截器的2種方式：

@Configuration
@EnableWebMvc // 這種方式會導(dǎo)致springSecurity的一些默認(rèn)配置失效
public class WebMvcConfigByConfigure implements WebMvcConfigurer{

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor());
    }
 }

```
@Configuration
public class WebMvcConfigBySupport extends DelegatingWebMvcConfiguration {

    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor());
    }
}
```
注意：當(dāng)使用第一種@EnableWebMvc+WebMvcConfigurer方式進(jìn)行實現(xiàn)時，會導(dǎo)致SpringSecurity的默認(rèn)配置失效，建議使用第二種，或者兩者結(jié)合使用，兩者結(jié)合時，需要將~~@EnableWebMvc~~進(jìn)行注釋，這樣Spring會將所有的配置進(jìn)行合并

處理器映射HandlerMapping：將程序中定義的映射記錄，會根據(jù)請求來判斷是否使用某個映射，即根據(jù)請求獲取到需要調(diào)用的方法，目前默認(rèn)有三個，

image-20211018162721377.png

在添加了@RequestMapping和@GetMapping等等注解的方法，會被注冊到HandlerMapping的mappingRegistry屬性中，請求進(jìn)來，會根據(jù)請求來匹配指定的方法

處理器適配器handlerAdapter：上一步找到了需要執(zhí)行的處理器，處理器適配器就是用來執(zhí)行處理器的，目前有4個

image-20211018172554141.png

方法參數(shù)處理器MethodArgumentResolver：方法的參數(shù)如何進(jìn)行解析，例如實現(xiàn)@RequestBody和@RequestParam等注解的功能(案例：自定義@CurrentUser注解，通過解析請求頭token來映射方法參數(shù)中的用戶信息)

案例實現(xiàn)：

public class CurrentUserMethodArgumentResolver implements HandlerMethodArgumentResolver {
    /**
     * 該處理器是否能處理這個參數(shù)
     * @param methodParameter
     * @return
     */
    @Override
    public boolean supportsParameter(MethodParameter methodParameter) {
        return methodParameter.hasParameterAnnotation(CurrentUser.class);
    }

    /**
     * 如何處理參數(shù)
     * @param methodParameter
     * @param modelAndViewContainer
     * @param nativeWebRequest
     * @param webDataBinderFactory
     * @return
     * @throws Exception
     */
    @Override
    public Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest, WebDataBinderFactory webDataBinderFactory) throws Exception {
        final String token = nativeWebRequest.getHeader("token");
        SysUser user= UserService.getUserFromToken(token);
        return user;
    }
}

@Configuration
public class WebMvcConfig extends WebMvcConfigurationSupport {

    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
    // 注冊參數(shù)處理器
        argumentResolvers.add(new CurrentUserMethodArgumentResolver());
    }


}

返回值處理器HandlerMethodReturnValueHandler：對于請求方法的返回值進(jìn)行處理

創(chuàng)建返回值處理器的方式

public class MyReturnHandlerResolver implements HandlerMethodReturnValueHandler {
    @Override
    public boolean supportsReturnType(MethodParameter methodParameter) {
        return methodParameter.hasMethodAnnotation(ParseReturn.class);
    }

    @Override
    public void handleReturnValue(Object o, MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest) throws Exception {
        //o就是返回值，根據(jù)業(yè)務(wù)情況進(jìn)行處理，例如對一個字段加減等等
    }
}

@Override
protected void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) {
    returnValueHandlers.add(new MyReturnHandlerResolver());
}

響應(yīng)體處理器RequestBodyAdvice：對于最后的數(shù)據(jù)進(jìn)行處理，定義如何向response寫出數(shù)據(jù)

實現(xiàn)RequestBodyAdvice的方式（可以多個，內(nèi)部最終合并為一個RequestBodyAdviceChain，處理器鏈）：

@ControllerAdvice
@ResponseBody
public class UnityExceptionHandler implements ResponseBodyAdvice<Object> {

    @ExceptionHandler(Exception.class)
    public Response<String> exception(Exception e){
        return Response.fail(e.getMessage());
    }


    // 是否進(jìn)行處理，根據(jù)自己的業(yè)務(wù)邏輯進(jìn)行判斷
    @Override
    public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
        return true;
    }

    // 真正的處理邏輯，如果上一步返回true，這一步進(jìn)行處理
    @Override
    public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
        if (body instanceof Response){
            return body;
        }else {
            return Response.success(body);
        }
    }
}

視圖解析器ViewResolver：例如像thymeleaf，freemaker 都實現(xiàn)了該接口，如何進(jìn)行視圖的渲染

文件請求解析器MultipartResolver：如果屬于文件上傳類的接口會使用到該解析器

代碼分析

DispatchServlet家族管理圖如下

image-20211019103720149.png

調(diào)用鏈路為：Servlet.service()->GenericServlet.service()->HttpServlet.service()->FrameWorkServlet.doGet()/doPost()...->FrameWorkServlet.processRequest()->DispatcherServlet.doService()->DispatcherServlet.doDispatch() 不管get還是post或其他請求最終都會調(diào)用processRequest方法，然后調(diào)用doService方法，最后是doDispatch方法，所以重點在doDispatch方法的邏輯。

doDispatch：

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
   HttpServletRequest processedRequest = request;
   HandlerExecutionChain mappedHandler = null;
   // 是否為文件上傳的請求標(biāo)識
   boolean multipartRequestParsed = false;

   WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

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

      try {
          // 是否文件上傳請求的判斷，如果是文件上傳請求，將普通Request轉(zhuǎn)換為MultipartHttpServletRequest對象
         processedRequest = checkMultipart(request);
         multipartRequestParsed = (processedRequest != request);

         // 通過HandlerMapping獲取處理方法，查看【分析1】.
         mappedHandler = getHandler(processedRequest);
         if (mappedHandler == null) {
             // 如果沒有處理的方法，返回異常，也就是我們看見的No mapping for GET '/user/get/123'
            noHandlerFound(processedRequest, response);
            return;
         }

         // 根據(jù)處理方法獲取該處理方法的適配器
         HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

         // Process last-modified header, if supported by the handler.
         String method = request.getMethod();
         boolean isGet = HttpMethod.GET.matches(method);
         if (isGet || HttpMethod.HEAD.matches(method)) {
            long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
            if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
               return;
            }
         }

          // 調(diào)用攔截器鏈中的開始方法，查看【分析2】
         if (!mappedHandler.applyPreHandle(processedRequest, response)) {
            return;
         }

         // 使用適配器調(diào)用處理方法，返回ModelAndView對象作為處理結(jié)果，查看【分析4】
         mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

         if (asyncManager.isConcurrentHandlingStarted()) {
            return;
         }
        // 根據(jù)返回的ModelAndView對象判斷是否需要設(shè)置默認(rèn)視圖，查看【分析5】
         applyDefaultViewName(processedRequest, mv);
          // 調(diào)用所有攔截器的postHandle方法，查看【分析6】
         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);
      }
       // 根據(jù)modelAndView進(jìn)行結(jié)果處理，查看【分析7】
      processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
   }
   catch (Exception ex) {
       // 異常結(jié)束也會調(diào)用攔截器的完成方法，查看【分析3】
      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);
         }
      }
   }
}

分析1：最終調(diào)用AbstractHandlerMethodMapping.getHandlerInternal()方法

protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
    // 獲取請求的路徑
   String lookupPath = initLookupPath(request);
   this.mappingRegistry.acquireReadLock();
   try {
       // 通過請求路徑從mappingRegistry獲取出處理該請求的方法，所有的可以處理請求的方法在項目啟動時都會注冊到mappingRegistry
      HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
      return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
   }
   finally {
      this.mappingRegistry.releaseReadLock();
   }
}

分析2：

boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
   for (int i = 0; i < this.interceptorList.size(); i++) {
      HandlerInterceptor interceptor = this.interceptorList.get(i);
       // 遍歷所有的攔截器并調(diào)用preHandle方法
      if (!interceptor.preHandle(request, response, this.handler)) {
          // 如果其中一個方法處理并攔截掉了，不再執(zhí)行后面的處理了，直接調(diào)用所有攔截器的完成方法
         triggerAfterCompletion(request, response, null);
         return false;
      }
      this.interceptorIndex = i;
   }
   return true;
}

分析3：調(diào)用所有攔截器的處理完成方法，很多地方有調(diào)用，例如出現(xiàn)了異常，都會回調(diào)攔截器的處理完成方法，注意：反向遍歷

void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex) {
   for (int i = this.interceptorIndex; i >= 0; i--) {
      HandlerInterceptor interceptor = this.interceptorList.get(i);
      try {
          // 調(diào)用所有攔截器的處理完成方法
         interceptor.afterCompletion(request, response, this.handler, ex);
      }
      catch (Throwable ex2) {
         logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
      }
   }
}

分析4：會調(diào)用RequestMappingHandlerAdapter.invokeHandlerMethod()方法

@Nullable
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
      HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {

   ServletWebRequest webRequest = new ServletWebRequest(request, response);
   try {
      WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
      ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);

      ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
       // 獲取所有的方法參數(shù)處理器（可以將請求傳遞的參數(shù)，封裝為java對象等等）
      if (this.argumentResolvers != null) {
         invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
      }
       // 獲取所有的返回結(jié)果處理器，(針對返回結(jié)果進(jìn)行處理)
      if (this.returnValueHandlers != null) {
         invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
      }
      ......省略代碼
         
         // 調(diào)用方法，并對參數(shù)和結(jié)果進(jìn)行處理，返回結(jié)果放在mavConatiner里面，查看【分析4-1】
      invocableMethod.invokeAndHandle(webRequest, mavContainer);
      if (asyncManager.isConcurrentHandlingStarted()) {
         return null;
      }
     // 獲取ModelAndView對象，查看【分析4-2】
      return getModelAndView(mavContainer, modelFactory, webRequest);
   }
   finally {
      webRequest.requestCompleted();
   }
}

分析4-1：

public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
      Object... providedArgs) throws Exception {

    // 反射調(diào)用方法，獲取最原始的返回結(jié)果
   Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
   setResponseStatus(webRequest);

   if (returnValue == null) {
      if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
         disableContentCachingIfNecessary(webRequest);
         mavContainer.setRequestHandled(true);
         return;
      }
   }
   else if (StringUtils.hasText(getResponseStatusReason())) {
      mavContainer.setRequestHandled(true);
      return;
   }

    // 這個值很重要，表示是否已經(jīng)處理了請求，例如直接返回的json數(shù)據(jù)時值為true，因為在返回值處理器時已經(jīng)將請求結(jié)果寫入response，返回視圖時，值為false
   mavContainer.setRequestHandled(false);
   Assert.state(this.returnValueHandlers != null, "No return value handlers");
   try {
       // 篩選出一個返回值處理器，使用返回值處理器處理返回結(jié)果，注意只有一個最合適的處理器進(jìn)行處理，并且該處理器的處理方法中會根據(jù)自身情況選擇設(shè)置mavContainer.setRequestHandled(false/true);表示自己是否處理返回結(jié)果，例如加了@ResponseBody的方法內(nèi)部就會將值設(shè)置為true，并且調(diào)用所有的RequestBodyAdvice鏈再次處理請求結(jié)果，最終結(jié)果直接寫入到Response，后續(xù)就不用再使用視圖解析器了
      this.returnValueHandlers.handleReturnValue(
            returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
   }
   catch (Exception ex) {
      if (logger.isTraceEnabled()) {
         logger.trace(formatErrorForReturnValue(returnValue), ex);
      }
      throw ex;
   }
}

分析4-2：將上一步的ModelAndViewContainer容器中獲取modelAndVIew對象進(jìn)行返回

@Nullable
private ModelAndView getModelAndView(ModelAndViewContainer mavContainer,
      ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception {

   modelFactory.updateModel(webRequest, mavContainer);
    // 重點，根據(jù)這個標(biāo)記值判斷是否已經(jīng)處理了返回請求，如果已經(jīng)處理了，返回modelAndView為null，外面就不會再調(diào)用viewResoler進(jìn)行視圖解析了
   if (mavContainer.isRequestHandled()) {
      return null;
   }
    // 如果沒有處理返回請求，使用ModelAndViewContainer封裝一個ModelAndView進(jìn)行返回
   ModelMap model = mavContainer.getModel();
   ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus());
   if (!mavContainer.isViewReference()) {
      mav.setView((View) mavContainer.getView());
   }
   if (model instanceof RedirectAttributes) {
      Map<String, ?> flashAttributes = ((RedirectAttributes) model).getFlashAttributes();
      HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
      if (request != null) {
         RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes);
      }
   }
   return mav;
}

分析5：

private void applyDefaultViewName(HttpServletRequest request, @Nullable ModelAndView mv) throws Exception {
    // 當(dāng)mv不為空&&mv沒有視圖時，當(dāng)我們自己的代碼邏輯返回String值時，該ModeAndView的view就為返回值，hasView方法的值就為true，結(jié)束執(zhí)行，但是當(dāng)返回值為null，或者方法為void時，hasView方法會返回false，就會執(zhí)行下面的方法，默認(rèn)將請求路徑作為視圖
   if (mv != null && !mv.hasView()) {
      String defaultViewName = getDefaultViewName(request);
      if (defaultViewName != null) {
         mv.setViewName(defaultViewName);
      }
   }
}

//例如：
/**
* 如果請求/template/test  則mv.hasView = true，因為view = test
* 如果請求/template/test2 則mv.hasView = false,因為view = null,然后執(zhí)行g(shù)etDefaultViewName，則mv.viewName = /template/test2（請求路徑）
* 請求/template/test3效果與請求/template/test2效果一致
**/
@Controller
@RequestMapping("/template")
public class TemplateController {

    @GetMapping("/test")
    public String test(ModelAndView mv){
        mv.addObject("name","張三");
        mv.addObject("age",18);
        return "test";
    }
    @GetMapping("/test2")
    public String test2(ModelAndView mv){
        mv.addObject("name","張三");
        mv.addObject("age",18);
        return null;
    }
    @GetMapping("/test3")
    public void test3(ModelAndView mv){
        mv.addObject("name","張三");
        mv.addObject("age",18);
    }
}

分析6：反向遍歷所有攔截器，依次調(diào)用postHandle方法

for (int i = this.interceptorList.size() - 1; i >= 0; i--) {
   HandlerInterceptor interceptor = this.interceptorList.get(i);
   interceptor.postHandle(request, response, this.handler, mv);
}

分析7：處理異常和視圖解析

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
      @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
      @Nullable Exception exception) throws Exception {

   boolean errorView = false;
 // 如果在執(zhí)行自定義邏輯方法時出現(xiàn)異常會執(zhí)行以下方法
   if (exception != null) {
      if (exception instanceof ModelAndViewDefiningException) {
         logger.debug("ModelAndViewDefiningException encountered", exception);
         mv = ((ModelAndViewDefiningException) exception).getModelAndView();
      }
      else {
         Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
          // 其他異常，調(diào)用異常處理器進(jìn)行處理，查看【分析7-1】
         mv = processHandlerException(request, response, handler, exception);
         errorView = (mv != null);
      }
   }

   // 當(dāng)mv不為空時才進(jìn)行視圖渲染，也可以看出，mavContainer.setRequestHandled(false);這個標(biāo)志位控制了是否渲染視圖
   if (mv != null && !mv.wasCleared()) {
       // 渲染視圖，查看【分析7-2】
      render(mv, request, response);
      if (errorView) {
         WebUtils.clearErrorRequestAttributes(request);
      }
   }
   else {
      if (logger.isTraceEnabled()) {
         logger.trace("No view rendering, null ModelAndView returned.");
      }
   }

   if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
      // Concurrent handling started during a forward
      return;
   }

   if (mappedHandler != null) {
      // 觸發(fā)所有攔截器的完成方法，查看【分析3】
      mappedHandler.triggerAfterCompletion(request, response, null);
   }
}

分析7-1：異常處理器處理請求，例如可以使用@ControllerAdvice+@ExceptionHandler進(jìn)行統(tǒng)一異常處理

@ControllerAdvice
@ResponseBody
public class MyExceptionHandler {
    @ExceptionHandler(RuntimeException.class)
    public String runtime(Exception e){
        return e.getMessage();
    }
}

分析7-2：

protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
   // 國際化信息
   Locale locale =
         (this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale());
   response.setLocale(locale);

   View view;
   String viewName = mv.getViewName();
   if (viewName != null) {
      // 視圖名稱不為空時使用所有的視圖解析器解析該名稱生成view對象，查看【分析7-2-1】
      view = resolveViewName(viewName, mv.getModelInternal(), locale, request);
      if (view == null) {
         throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
               "' in servlet with name '" + getServletName() + "'");
      }
   }
   else {
      // 如果視圖名為空，則查看modelAndView中的view是否為空，不為空則返回，為空異常
      view = mv.getView();
      if (view == null) {
         throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
               "View object in servlet with name '" + getServletName() + "'");
      }
   }

   // Delegate to the View object for rendering.
   if (logger.isTraceEnabled()) {
      logger.trace("Rendering view [" + view + "] ");
   }
   try {
      if (mv.getStatus() != null) {
         response.setStatus(mv.getStatus().value());
      }
       // 使用view和mv請求等信息進(jìn)行視圖渲染，將結(jié)果寫入到response
      view.render(mv.getModelInternal(), request, response);
   }
   catch (Exception ex) {
      if (logger.isDebugEnabled()) {
         logger.debug("Error rendering view [" + view + "]", ex);
      }
      throw ex;
   }
}

分析7-2-1：

@Nullable
protected View resolveViewName(String viewName, @Nullable Map<String, Object> model,
      Locale locale, HttpServletRequest request) throws Exception {

   if (this.viewResolvers != null) {
       // 調(diào)用所有的視圖解析器解析名稱，獲得view，所有的模板引擎也就是實現(xiàn)了viewResolver，使用自己的邏輯進(jìn)行視圖解析，例如freemaker默認(rèn)解析路徑為 classpath:/template下面后綴名為html的文件，例如viewName為test,則找到的文件則是classpath:/template/test.html,然后將該文件解析為view對象返回
      for (ViewResolver viewResolver : this.viewResolvers) {
         View view = viewResolver.resolveViewName(viewName, locale);
         if (view != null) {
            return view;
         }
      }
   }
   return null;
}

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SpringBoot之DispatchServlet流程

SpringBoot之DispatchServlet流程

前言

使用到的組件

代碼分析

相關(guān)閱讀更多精彩內(nèi)容

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SpringBoot之DispatchServlet流程

前言

使用到的組件

代碼分析

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容

色偷偷精品伊人,欧洲久久精品,欧美综合婷婷骚逼,国产AV主播,国产最新探花在线,九色在线视频一区,伊人大交九欧美,1769亚洲,黄色成人av