# Spring mvc 源码剖析 ## 一、DispatcherServlet继承结构 ![img_6](https://img.zhaojq.top/20260727092020316.png "img_6") ## 二、重要时机点分析 ### 1.handler方法执行时机 ![img_7](https://img.zhaojq.top/20260727092020541.png "img_7") ![img_8](https://img.zhaojq.top/20260727092020726.png "img_8") `doDispatch`方法的 `ha.handle`方法调用 ### 2.页面渲染时机 jsp页面打断点 ![img_9](https://img.zhaojq.top/20260727092020965.png "img_9") 调用了` processDispatchResult` Spring处理请求的流程为： 1. 调⽤getHandler()获取到能够处理当前请求的执⾏链 HandlerExecutionChain(handler+拦截器) 2. 调⽤getHandlerAdapter()；获取能够执⾏1中Handler的适配器 3. 适配器调⽤Handler执⾏ha.handle（总会返回⼀个ModelAndView对象） 4. 调⽤processDispatchResult()⽅法完成视图渲染跳转 ```java 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 { //检查是否是文件上传请求 processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // Determine handler for the current request. //取得处理当前请求的Controller，这⾥也称为Handler，即处理器 //这⾥并不是直接返回 Controller，⽽是返回 HandlerExecutionChain 请求处理链对象 //该对象封装了Handler和Inteceptor mappedHandler = getHandler(processedRequest); if (mappedHandler == null) { // 如果 handler 为空，则返回404 noHandlerFound(processedRequest, response); return; } // Determine handler adapter for the current request. //获取处理请求的处理器适配器 HandlerAdapter HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); // Process last-modified header, if supported by the handler. //处理 last-modified 请求头 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. //实际处理器处理请求，返回结果视图对象 mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } //结果视图对象的处理 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); } //跳转⻚⾯，渲染视图 processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } catch (Exception ex) { //最终会调⽤HandlerInterceptor的afterCompletion ⽅法 triggerAfterCompletion(processedRequest, response, mappedHandler, ex); } catch (Throwable err) { //最终会调⽤HandlerInterceptor的afterCompletion ⽅法 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); } } } } ``` ## 三、核心步骤getHandler剖析 ![img_10](https://img.zhaojq.top/20260727092021204.png "img_10") 遍历handlerMapping，获取能够处理当前请求的执行链 ## 四、核心步骤getHandlerAdapter ![img_11](https://img.zhaojq.top/20260727092021413.png "img_11") 遍历各个HandlerAdapter，看哪个Adapter⽀持处理当前Handler ## 五、ha.handle方法剖析 ![img_12](https://img.zhaojq.top/20260727092021640.png "img_12") ![img_13](https://img.zhaojq.top/20260727092021881.png "img_13") ![img_14](https://img.zhaojq.top/20260727092022096.png "img_14") ## 六、核⼼步骤processDispatchResult⽅法剖析 ![img_15](https://img.zhaojq.top/20260727092022312.png "img_15") ![img_16](https://img.zhaojq.top/20260727092022554.png "img_16") ![img_17](https://img.zhaojq.top/20260727092022790.png "img_17") ## 七、spring mvc九大组件初始化 DispatcherServlet中9个属性（组件） ```java /** MultipartResolver used by this servlet. */ //多部件解析器 @Nullable private MultipartResolver multipartResolver; /** LocaleResolver used by this servlet. */ //国际化解析器 @Nullable private LocaleResolver localeResolver; /** ThemeResolver used by this servlet. */ //主题解析器 @Nullable private ThemeResolver themeResolver; /** List of HandlerMappings used by this servlet. */ //处理器映射器 @Nullable private List handlerMappings; /** List of HandlerAdapters used by this servlet. */ //处理器适配器 @Nullable private List handlerAdapters; /** List of HandlerExceptionResolvers used by this servlet. */ //异常解析器 @Nullable private List handlerExceptionResolvers; /** RequestToViewNameTranslator used by this servlet. */ //默认视力名解析器 @Nullable private RequestToViewNameTranslator viewNameTranslator; /** FlashMapManager used by this servlet. */ //flash属性管理组件 @Nullable private FlashMapManager flashMapManager; /** List of ViewResolvers used by this servlet. */ //视力解析器 @Nullable private List viewResolvers; ``` 初始化时机 ![img_18](https://img.zhaojq.top/20260727092022997.png "img_18") ![img_19](https://img.zhaojq.top/20260727092023212.png "img_19") ```java //如果还为空，则按照默认策略生成 if (this.handlerMappings == null) { this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class); if (logger.isTraceEnabled()) { logger.trace("No HandlerMappings declared for servlet '" + getServletName() + "': using default strategies from DispatcherServlet.properties"); } } //从以下配置文件中找 /** * Name of the class path resource (relative to the DispatcherServlet class) * that defines DispatcherServlet's default strategy names. */ private static final String DEFAULT_STRATEGIES_PATH = "DispatcherServlet.properties"; // ``` ![img_20](https://img.zhaojq.top/20260727092023468.png "img_20")