本文共 18580 字，大约阅读时间需要 61 分钟。

开发工具 Intellij IDEA 

目标、调试 请求http://localhost:8080/coffee/helloworld

           
    
     dispatcher
            
    
     org.springframework.web.servlet.DispatcherServlet
            
                
     
      contextConfigLocation
                 
     
      /WEB-INF/dispatcher-servlet.xml
             
            
    
     1
        
       
           
    
     dispatcher
            
    
     /coffee
        
   

@Controller@RequestMapping("coffee")public class HelloControler{	@RequestMapping("helloworld")	public @ResponseBody String helloWorld() {		System.out.println("xxx");		return "hello 222 world";	}}

/** * Delegate GET requests to processRequest/doService. * 
Will also be invoked by HttpServlet's default implementation of {@code doHead}, * with a {@code NoBodyResponse} that just captures the content length. * @see #doService * @see #doHead */@Overrideprotected final void doGet(HttpServletRequest request, HttpServletResponse response)      throws ServletException, IOException {   processRequest(request, response);}

org.springframework.web.servlet.FrameworkServlet

/**	 * Process this request, publishing an event regardless of the outcome.	 * 
The actual event handling is performed by the abstract	 * {@link #doService} template method.	 */	protected final void processRequest(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		long startTime = System.currentTimeMillis();		Throwable failureCause = null;		LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();		LocaleContext localeContext = buildLocaleContext(request);		RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();		ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes);		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);		asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor());		initContextHolders(request, localeContext, requestAttributes);		try {			doService(request, response);//******* doService *********//		}		catch (ServletException ex) {			failureCause = ex;			throw ex;		}		catch (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();			}			if (logger.isDebugEnabled()) {				if (failureCause != null) {					this.logger.debug("Could not complete request", failureCause);				}				else {					if (asyncManager.isConcurrentHandlingStarted()) {						logger.debug("Leaving response open for concurrent processing");					}					else {						this.logger.debug("Successfully completed request");					}				}			}			publishRequestHandledEvent(request, response, startTime, failureCause);		}	}

/**	 * Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch}	 * for the actual dispatching.	 */	@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
   
     attributesSnapshot = null;		if (WebUtils.isIncludeRequest(request)) {			attributesSnapshot = new HashMap
    
     ();			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);				}			}		}	}
    
   

/**	 * Process the actual dispatching to the handler.	 * 
The handler will be obtained by applying the servlet's HandlerMappings in order.	 * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters	 * to find the first that supports the handler class.	 * 
All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers	 * themselves to decide which methods are acceptable.	 * @param request current HTTP request	 * @param response current HTTP response	 * @throws Exception in case of any kind of processing failure	 */	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);// **********************************根据request查找mappedHandler 也就是一个Controller				// Determine handler for the current request.				mappedHandler = getHandler(processedRequest);				if (mappedHandler == null || mappedHandler.getHandler() == 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 (logger.isDebugEnabled()) {						logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);					}					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);				}			}		}	}

/**	 * Return the HandlerExecutionChain for this request.	 * 
Tries all handler mappings in order.	 * @param request current HTTP request	 * @return the HandlerExecutionChain, or {@code null} if no handler could be found	 */	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;	}

private List
   
     handlerMappings;
   

BeanNameUrlHandlerMapping DefaultAnnotationHandlerMapping package org.springframework.web.servlet.handler; /**	 * Look up a handler for the given request, falling back to the default	 * handler if no specific one is found.	 * @param request current HTTP request	 * @return the corresponding handler instance, or the default handler	 * @see #getHandlerInternal	 */	@Override	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;	} package org.springframework.web.servlet.handler; /**	 * Look up a handler for the URL path of the given request.	 * @param request current HTTP request	 * @return the handler instance, or {@code null} if none found	 */	@Override	protected Object getHandlerInternal(HttpServletRequest request) throws Exception {		String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);//coffee/helloworld *** 往下看		Object handler = lookupHandler(lookupPath, request);		if (handler == null) {			// We need to care for the default handler directly, since we need to			// expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.			Object rawHandler = null;			if ("/".equals(lookupPath)) {				rawHandler = getRootHandler();			}			if (rawHandler == null) {				rawHandler = getDefaultHandler();			}			if (rawHandler != null) {				// Bean name or resolved handler?				if (rawHandler instanceof String) {					String handlerName = (String) rawHandler;					rawHandler = getApplicationContext().getBean(handlerName);				}				validateHandler(rawHandler, request);				handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);			}		}		if (handler != null && logger.isDebugEnabled()) {			logger.debug("Mapping [" + lookupPath + "] to " + handler);		}		else if (handler == null && logger.isTraceEnabled()) {			logger.trace("No handler mapping found for [" + lookupPath + "]");		}		return handler;	} package org.springframework.web.util; class UrlPathHelper  public String getLookupPathForRequest(HttpServletRequest request) {        if(this.alwaysUseFullPath) {            return this.getPathWithinApplication(request);        } else {            String rest = this.getPathWithinServletMapping(request);//运行结果 --> ""            return !"".equals(rest)?rest:this.getPathWithinApplication(request);//执行getpathWithApplication 返回 /coffee/helloworld        }    } 上面的方法执行的是else public String getPathWithinServletMapping(HttpServletRequest request) {        String pathWithinApp = this.getPathWithinApplication(request);//coffee/helloworld  ******往下看        String servletPath = this.getServletPath(request);//coffee/helloworld  ******往下看        String sanitizedPathWithinApp = this.getSanitizedPath(pathWithinApp);        String path;        if(servletPath.contains(sanitizedPathWithinApp)) {            path = this.getRemainingPath(sanitizedPathWithinApp, servletPath, false); //结果 ""        } else {            path = this.getRemainingPath(pathWithinApp, servletPath, false);        }        if(path != null) {            return path; // 返回 ""        } else {            String pathInfo = request.getPathInfo();            if(pathInfo != null) {                return pathInfo;            } else {                if(!this.urlDecode) {                    path = this.getRemainingPath(this.decodeInternal(request, pathWithinApp), servletPath, false);                    if(path != null) {                        return pathWithinApp;                    }                }                return servletPath;            }        }    } public String getPathWithinApplication(HttpServletRequest request) {        String contextPath = this.getContextPath(request);// ""        String requestUri = this.getRequestUri(request);//coffee/helloworld        String path = this.getRemainingPath(requestUri, contextPath, true);//coffee/helloworld        return path != null?(StringUtils.hasText(path)?path:"/"):requestUri;//coffee/helloworld    }  public String getContextPath(HttpServletRequest request) {        String contextPath = (String)request.getAttribute("javax.servlet.include.context_path");        if(contextPath == null) {            contextPath = request.getContextPath();        }        if("/".equals(contextPath)) {///*****注意一下这个方法如果            contextPath = "";        }        return this.decodeRequestString(request, contextPath);    } public String getServletPath(HttpServletRequest request) {        String servletPath = (String)request.getAttribute("javax.servlet.include.servlet_path");        if(servletPath == null) {            servletPath = request.getServletPath();//*******/coffee/helloworld        }        if(servletPath.length() > 1 && servletPath.endsWith("/") && this.shouldRemoveTrailingServletPathSlash(request)) {            servletPath = servletPath.substring(0, servletPath.length() - 1);        }        return servletPath;    } /**	 * Look up a handler instance for the given URL path.	 * 
Supports direct matches, e.g. a registered "/test" matches "/test",	 * and various Ant-style pattern matches, e.g. a registered "/t*" matches	 * both "/test" and "/team". For details, see the AntPathMatcher class.	 * 
Looks for the most exact pattern, where most exact is defined as	 * the longest path pattern.	 * @param urlPath URL the bean is mapped to	 * @param request current HTTP request (to expose the path within the mapping to)	 * @return the associated handler instance, or {@code null} if not found	 * @see #exposePathWithinMapping	 * @see org.springframework.util.AntPathMatcher	 */	protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {		// Direct match? *************************************下面一行代码是真正查询Controller的方法		Object handler = this.handlerMap.get(urlPath);		if (handler != null) {			// Bean name or resolved handler?			if (handler instanceof String) {				String handlerName = (String) handler;				handler = getApplicationContext().getBean(handlerName);			}			validateHandler(handler, request);			return buildPathExposingHandler(handler, urlPath, urlPath, null);		}		// Pattern match?		List
    
      matchingPatterns = new ArrayList
     
      ();		for (String registeredPattern : this.handlerMap.keySet()) {			if (getPathMatcher().match(registeredPattern, urlPath)) {				matchingPatterns.add(registeredPattern);			}			else if (useTrailingSlashMatch()) {				if (!registeredPattern.endsWith("/") && getPathMatcher().match(registeredPattern + "/", urlPath)) {					matchingPatterns.add(registeredPattern +"/");				}			}		}		String bestPatternMatch = null;		Comparator
      
        patternComparator = getPathMatcher().getPatternComparator(urlPath);		if (!matchingPatterns.isEmpty()) {			Collections.sort(matchingPatterns, patternComparator);			if (logger.isDebugEnabled()) {				logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);			}			bestPatternMatch = matchingPatterns.get(0);		}		if (bestPatternMatch != null) {			handler = this.handlerMap.get(bestPatternMatch);			if (handler == null) {				Assert.isTrue(bestPatternMatch.endsWith("/"));				handler = this.handlerMap.get(bestPatternMatch.substring(0, bestPatternMatch.length() - 1));			}			// Bean name or resolved handler?			if (handler instanceof String) {				String handlerName = (String) handler;				handler = getApplicationContext().getBean(handlerName);			}			validateHandler(handler, request);			String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestPatternMatch, urlPath);			// There might be multiple 'best patterns', let's make sure we have the correct URI template variables			// for all of them			Map
       
         uriTemplateVariables = new LinkedHashMap
        
         (); for (String matchingPattern : matchingPatterns) { if (patternComparator.compare(bestPatternMatch, matchingPattern) == 0) { Map
         
           vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath); Map
          
            decodedVars = getUrlPathHelper().decodePathVariables(request, vars); uriTemplateVariables.putAll(decodedVars); } } if (logger.isDebugEnabled()) { logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables); } return buildPathExposingHandler(handler, bestPatternMatch, pathWithinMapping, uriTemplateVariables); } // No handler found... return null; }
          
         
        
       
      
     
    

转载地址：https://blog.csdn.net/id19870510/article/details/53098834 如侵犯您的版权，请留言回复原文章的地址，我们会给您删除此文章，给您带来不便请您谅解！