框架流程图
springmvc的核心类org.springframework.web.servlet.DispatcherServlet,是一个servlet,间接继承了httpservlet;重写了doService方法
@Override protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception { if (logger.isDebugEnabled()) { String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : ""; logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed + " processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]"); } // Keep a snapshot of the request attributes in case of an include, // to be able to restore the original attributes after the include. Map<String, Object> attributesSnapshot = null; if (WebUtils.isIncludeRequest(request)) { attributesSnapshot = new HashMap<String, Object>(); Enumeration<?> attrNames = request.getAttributeNames(); while (attrNames.hasMoreElements()) { String attrName = (String) attrNames.nextElement(); if (this.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet")) { attributesSnapshot.put(attrName, request.getAttribute(attrName)); } } } // Make framework objects available to handlers and view objects. request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext()); request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver); request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver); request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource()); FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response); if (inputFlashMap != null) { request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap)); } request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap()); request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager); try { 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); } } } }
最重要的就是执行了 doDispatch(request, response);都只是对参数的处理
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); //为当前请求确定处理器 mappedHandler = getHandler(processedRequest); if (mappedHandler == null || mappedHandler.getHandler() == null) { noHandlerFound(processedRequest, response); return; } //为当前请求确定处理程序适配器。 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; } } //执行所有拦截器的preHandle方法,如果有拦截器的prhandle方法返回false就直接结束,return if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } // 由适配器调用实际的处理器 mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } //将逻辑路径转换为物理路径,将配置文件中配置的前缀和后缀拼接上返回的视图名字; applyDefaultViewName(processedRequest, mv);
//执行所有拦截器的postHandle方法 mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException = ex; } processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } catch (Exception ex) { triggerAfterCompletion(processedRequest, response, mappedHandler, ex); } catch (Error err) { triggerAfterCompletionWithError(processedRequest, response, mappedHandler, 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); } } } }
一 首先前端控制器获取到请求,首先获取到请求有没有文件的上传,调用方法
processedRequest = checkMultipart(request);
protected HttpServletRequest checkMultipart(HttpServletRequest request) throws MultipartException { if (this.multipartResolver != null && this.multipartResolver.isMultipart(request)) { if (WebUtils.getNativeRequest(request, MultipartHttpServletRequest.class) != null) { logger.debug("Request is already a MultipartHttpServletRequest - if not in a forward, " + "this typically results from an additional MultipartFilter in web.xml"); } else if (request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) instanceof MultipartException) { logger.debug("Multipart resolution failed for current request before - " + "skipping re-resolution for undisturbed error rendering"); } else { return this.multipartResolver.resolveMultipart(request); } } // If not returned before: return original request. return request; }
二.然后调用mappedHandler = getHandler(processedRequest),在这个方法中再调用处理器映射器的getHandler(processedRequest)方法
1.遍历所有的处理器映射器,
2.获取到xml中配置的处理器映射器,或者没有配置使用默认的处理器映射器;
3.然后有处理器映射器调用getHandler(request)方法,返回处理器执行链
3.1通过url获取处理器,如果获取不到,就会走默认的处理器,如果还没有,就返回null;
3.2同时看处理器是否是字符串,如果是字符串就通这个字符串去spring工厂中找到这个处理器
43.3然后通过处理器获取到处理器执行链,然后返回处理器执行链(包含处理器,拦截器链,拦截器prehander方法执行到那一个拦截器在拦截器链中的下标)
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { for (HandlerMapping hm : this.handlerMappings) { if (logger.isTraceEnabled()) { logger.trace( "Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'"); } HandlerExecutionChain handler = hm.getHandler(request); if (handler != null) { return handler; } } return null; }
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { 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); } HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request); if (CorsUtils.isCorsRequest(request)) { CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request); CorsConfiguration handlerConfig = getCorsConfiguration(handler, request); CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig); executionChain = getCorsHandlerExecutionChain(request, executionChain, config); } return executionChain; }
三.通过处理器执行链(HandlerExecutionChain)找到对应的处理器适配器(HandlerAdapter)
调用HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler())
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException { for (HandlerAdapter ha : this.handlerAdapters) { if (logger.isTraceEnabled()) { logger.trace("Testing handler adapter [" + ha + "]"); } if (ha.supports(handler)) { return ha; } } throw new ServletException("No adapter for handler [" + handler + "]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler"); }
四:执行处理器执行链中的applyPreHandle(processedRequest, response)方法,并且进行了判断,是false就直接return
if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; }
applyPreHandle(processedRequest, response)方法:
1.循环执行处理器执行链中的拦截器链的preHandle方法,如果都没有拦截,就直接走下一步
2.如果有拦截器拦截了,
2-1.preHandle方法返回了false,就记录下这个拦截器的前一个的下标,就是记录所有已经执行了prehandler方法返回true的拦截器,
2-2.然后遍历已经执行了prehandler方法返回true的拦截器,再执行他们的afterCompletion方法
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception { HandlerInterceptor[] interceptors = getInterceptors(); if (!ObjectUtils.isEmpty(interceptors)) { for (int i = 0; i < interceptors.length; i++) { HandlerInterceptor interceptor = interceptors[i]; if (!interceptor.preHandle(request, response, this.handler)) { triggerAfterCompletion(request, response, null); return false; } this.interceptorIndex = i; } } return true; }
所以当有拦截器拦截了时,就不执行下面的代码了,直接return,但是在return之前会执行已经执行了prehandler方法返回true的拦截器的afterCompletion方法
当没有拦截器拦截时执行
六:通过适配器执行处理器,并且返回一个ModelAndView,模型视图对象
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
七:然后将ModelAndView传递给ViewResolver视图解析器,将逻辑视图转换为物理视图,就是拼接xml中的配置的前缀和后缀,然后返回一个视图对象
applyDefaultViewName(processedRequest, mv);
private void applyDefaultViewName(HttpServletRequest request, ModelAndView mv) throws Exception { if (mv != null && !mv.hasView()) { mv.setViewName(getDefaultViewName(request)); } }
protected String getDefaultViewName(HttpServletRequest request) throws Exception { return this.viewNameTranslator.getViewName(request); }
public String getViewName(HttpServletRequest request) { String lookupPath = this.urlPathHelper.getLookupPathForRequest(request); return (this.prefix + transformPath(lookupPath) + this.suffix); }
八:mappedHandler.applyPostHandle(processedRequest, response, mv);执行所有拦截器的postHandler方法,并且遍历是逆序遍历的,所以后配置的会先执行postHandler方法
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) throws Exception { HandlerInterceptor[] interceptors = getInterceptors(); if (!ObjectUtils.isEmpty(interceptors)) { for (int i = interceptors.length - 1; i >= 0; i--) { HandlerInterceptor interceptor = interceptors[i]; interceptor.postHandle(request, response, this.handler, mv); } } }
九都是捕获异常的操作,捕获到异常之后最后还是会执行已经执行了prehandler方法返回true的拦截器的afterCompletion方法
catch (Exception ex) { triggerAfterCompletion(processedRequest, response, mappedHandler, ex); } catch (Error err) { triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err); }
private void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, Exception ex) throws Exception { if (mappedHandler != null) { mappedHandler.triggerAfterCompletion(request, response, ex); } throw ex; } private void triggerAfterCompletionWithError(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, Error error) throws Exception { ServletException ex = new NestedServletException("Handler processing failed", error); if (mappedHandler != null) { mappedHandler.triggerAfterCompletion(request, response, ex); } throw ex; }
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, Exception ex) throws Exception { HandlerInterceptor[] interceptors = getInterceptors(); if (!ObjectUtils.isEmpty(interceptors)) { for (int i = this.interceptorIndex; i >= 0; i--) { HandlerInterceptor interceptor = interceptors[i]; try { interceptor.afterCompletion(request, response, this.handler, ex); } catch (Throwable ex2) { logger.error("HandlerInterceptor.afterCompletion threw exception", ex2); } } } }
最后就是对如果是文件上传的话,进行关流等操作
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); } } }
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