讲这个之前,我们得先知道在SpringMvc启动时,会加载所有的Bean类,就是加了@Controller,@Component等组件标识的类,然后会把@RequestMapping的方法也加入到一个集合。放入到上下文环境中。
发起请求后的执行流程是:检查request类型-->获取匹配的Handlemethod-->查找拦截器-->组成HandlerExecutionChain执行链-->获取方法执行链对象的适配器(HandlerAdapter)-->然后反射执行业务方法。
有一个大概的了解之后,开始源码分析:
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 = ; Exception dispatchException = ; { processedRequest = checkMultipart(request); multipartRequestParsed = processedRequest != request; // Determine handler for the current request.
//获取匹配的执行链
mappedHandler = getHandler(processedRequest); if (mappedHandler == null || mappedHandler.getHandler() == ) { noHandlerFound(processedRequest,response); return; } Determine handler adapter for the current request.
//根据匹配到的执行链对象,获取合适的适配器
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()) { String requestUri = urlPathHelper.getRequestUri(request); logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified); } if (new ServletWebRequest(request,response).checkNotModified(lastModified) && isGet) { ; } } if (!mappedHandler.applyPreHandle(processedRequest,response)) { { Actually invoke the handler.
//在这里面反射执行业务方法
mv = ha.handle(processedRequest,response,mappedHandler.getHandler()); } finally (asyncManager.isConcurrentHandlingStarted()) { ; } } applyDefaultViewName(request,mv); mappedHandler.applyPostHandle(processedRequest,mv); } catch (Exception ex) { dispatchException = ex; } processDispatchResult(processedRequest,mappedHandler,mv,dispatchException); } (Exception ex) { triggerAfterCompletion(processedRequest,ex); } (Error err) { triggerAfterCompletionWithError(processedRequest,err); } { (asyncManager.isConcurrentHandlingStarted()) { Instead of postHandle and afterCompletion mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest,response); ; } Clean up any resources used by a multipart request. (multipartRequestParsed) { cleanupMultipart(processedRequest); } } }
从标红部分点进去,到AbstractHandlerMethodAdapter类的handle方法-->RequestMappingHandlerAdapter类的handleInternal方法-->RequestMappingHandlerAdapter类的invokeHandleMethod
-->RequestMappingHandlerAdapter类的invokeAndHandle-->ServletInvocableHandlerMethod类的invokeForRequest-->InvocableHandlerMethod类的invokeForRequest。该方法代码如下:
public final Object invokeForRequest(NativeWebRequest request,ModelAndViewContainer mavContainer,Object... providedArgs) Exception { Object[] args = getMethodArgumentValues(request,mavContainer,providedArgs); (logger.isTraceEnabled()) { StringBuilder sb = new StringBuilder("Invoking ["); sb.append(this.getBeanType().getSimpleName()).append("."); sb.append(getMethod().getName()).append("] method with arguments "); sb.append(Arrays.asList(args)); logger.trace(sb.toString()); }
//执行方法 Object returnValue = invoke(args); (logger.isTraceEnabled()) { logger.trace("Method [" + getMethod().getName() + "] returned [" + returnValue + "]"); } returnValue; }
然后就可以执行方法了。需要注意的是匹配方法时,根据@RequestMapping里面的value路径来匹配的,如果匹配到的有多个,如你配置了通配符,也配置了精确配置,他都会匹配到放在一个集合中,根据规则排序,然后取集合的第一个元素。有兴趣的可以看看这个排序的规则,理论上肯定是路径越精确的会优先,具体代码实现如下:
protected HandlerMethod lookupHandlerMethod(String lookupPath,HttpServletRequest request) Exception { List<Match> matches = new ArrayList<Match>(); List<T> directPathMatches = this.urlMap.get(lookupPath); if (directPathMatches != ) { addMatchingMappings(directPathMatches,matches,request); } (matches.isEmpty()) { No choice but to go through all mappings addMatchingMappings(.handlerMethods.keySet(),1)">matches.isEmpty()) {
//排序规则 Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
//进行排序 Collections.sort(matches,comparator); (logger.isTraceEnabled()) { logger.trace("Found " + matches.size() + " matching mapping(s) for [" + lookupPath + "] : " + matches); } Match bestMatch = matches.get(0); if (matches.size() > 1) { Match secondBestMatch = matches.get(1); if (comparator.compare(bestMatch,secondBestMatch) == 0) { Method m1 = bestMatch.handlerMethod.getMethod(); Method m2 = secondBestMatch.handlerMethod.getMethod(); throw IllegalStateException( "Ambiguous handler methods mapped for HTTP path '" + request.getRequestURL() + "': {" + m1 + "," + m2 + "}"); } } handleMatch(bestMatch.mapping,lookupPath,request); bestMatch.handlerMethod; } else handleNoMatch(handlerMethods.keySet(),request); } }
原文地址:https://www.cnblogs.com/javammc
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