SpringMVC源碼分析之DispatcherServlet
1.DispatcherServlet的初始化
前面一片文章大概的講述了DispatcherServlet的基本作用，也知道它其實就是一個Servlet，下面詳細分析DispatcherServlet。
Web容器初始化後，會爲每個Servlet創建對象，並加載其上下文環境。我們都知道，在Tomcat容器中，維護了一個線程池，每當有一個客戶請求抵達服務器的時候，就分配一個線程來處理該請求。同時，Servlet是單例多線程的，也就是多個請求共用一個Servlet容器。所以呢，DispatcherServlet的完整定義是：是一個具有唯一性的增強型Servlet容器。 明確了這一點，我們就可以想象的到，DispatcherServlet具有servlet的大多數特性，包括Servlet的完整生命週期。
Spring中通過DispatcherServlet來處理所用的請求！爲什麼這樣設計呢？具體可以參考前端設計模式
分析初始化之前先了解一下DispatcherServlet的繼承關係:
首先瞭解到Servlet的初始化時會調用其inti(),DispatcherServlet也不例外。發現DispatcherServlet中沒有該方法，繼續向上看。FrameworkServlet中也沒有，繼續向上；發現HttpServletBean存在。
public final void init() throws ServletException {
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
if (!pvs.isEmpty()) {
try {
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
//這裏就是加載servlet的環境吧
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
initBeanWrapper(bw);
bw.setPropertyValues(pvs, true);
}
catch (BeansException ex) {
if (logger.isErrorEnabled()) {
logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
}
throw ex;
}
}
// Let subclasses do whatever initialization they like.
//重點關注這個方法
initServletBean();
}
發現其中調用了initServletBean(),發現在HttpServletBean沒有具體實現，看他的子類FrameworkServlet,其中得到了webApplicationContext對象，在之前，ContextLoaderListener加載的時候已經創建了WebApplicationContext實例（具體可以查看ContextLoaderListener源碼分析），而在這裏是對這個實例的進一步補充初始化。這個方法在HttpServletBean的子類FrameworkServlet中得到了重寫。
注：ContextLoaderListener載入的是除DispatcherServlet之外的其他的上下文配置文件，而Spring MVC的配置文件是在DispatcherServlet中設置的。
protected final void initServletBean() throws ServletException {
try {
//initWebApplicationContext()來得到webApplicationContext對象
this.webApplicationContext = initWebApplicationContext();
initFrameworkServlet();
}
catch (ServletException ex) {
this.logger.error("Context initialization failed", ex);
throw ex;
}
catch (RuntimeException ex) {
this.logger.error("Context initialization failed", ex);
throw ex;
}
}
initFrameworkServlet()是給子類來覆蓋的方法，但是我在DispatcherServlet中並沒有找到，查看initWebApplicationContext()，還是在FrameWorkServlet中。
protected WebApplicationContext initWebApplicationContext() {
WebApplicationContext rootContext = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
WebApplicationContext wac = null;
if (this.webApplicationContext != null) {
// A context instance was injected at construction time -> use it
wac = this.webApplicationContext;
if (wac instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent -> set
// the root application context (if any; may be null) as the parent
cwac.setParent(rootContext);
}
configureAndRefreshWebApplicationContext(cwac);
}
}
}
if (wac == null) {
// No context instance was injected at construction time -> see if one
// has been registered in the servlet context. If one exists, it is assumed
// that the parent context (if any) has already been set and that the
// user has performed any initialization such as setting the context id
wac = findWebApplicationContext();
}
if (wac == null) {
// No context instance is defined for this servlet -> create a local one
wac = createWebApplicationContext(rootContext);
}
if (!this.refreshEventReceived) {
// Either the context is not a ConfigurableApplicationContext with refresh
// support or the context injected at construction time had already been
// refreshed -> trigger initial onRefresh manually here.
onRefresh(wac);
}
if (this.publishContext) {
// Publish the context as a servlet context attribute.
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
"' as ServletContext attribute with name [" + attrName + "]");
}
}
return wac;
}
initWebApplicationContext()方法主要用於創建或刷新WebApplicationContext實例，並對Servlet功能所使用的一些環境變量進行初始化。首先通過findWebApplicationContext()中調用getContextAttribute()來查找ServletContext進行初始化webApplicationContext實例。如果沒有，就通過ContextLoaderListener獲得的rootContext重新創建一個實例createWebApplicationContext(rootContext)。
protected WebApplicationContext findWebApplicationContext() {
String attrName = getContextAttribute();
if (attrName == null) {
return null;
}
WebApplicationContext wac =
WebApplicationContextUtils.getWebApplicationContext(getServletContext(), attrName);
if (wac == null) {
throw new IllegalStateException("No WebApplicationContext found: initializer not registered?");
}
return wac;
}
protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
Class<?> contextClass = getContextClass();
if (this.logger.isDebugEnabled()) {
this.logger.debug("Servlet with name '" + getServletName() +
"' will try to create custom WebApplicationContext context of class '" +
contextClass.getName() + "'" + ", using parent context [" + parent + "]");
}
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
throw new ApplicationContextException(
"Fatal initialization error in servlet with name '" + getServletName() +
"': custom WebApplicationContext class [" + contextClass.getName() +
"] is not of type ConfigurableWebApplicationContext");
}
ConfigurableWebApplicationContext wac =
(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
//這裏設置實例的一些參數屬性
wac.setEnvironment(getEnvironment());
wac.setParent(parent);
wac.setConfigLocation(getContextConfigLocation());
configureAndRefreshWebApplicationContext(wac);
return wac;
}
這些操作都是對webApplicationContext實例的進一步初始化！那麼Servlet中配置文件的加載和與rootContext整合是如何進行的？（webApplicationContext是所有Servlet的父環境！），答案是在initWebApplicationContext()中的configureAndRefreshWebApplicationContext()調用的refresh();
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
// The application context id is still set to its original default value
// -> assign a more useful id based on available information
if (this.contextId != null) {
wac.setId(this.contextId);
}
else {
// Generate default id...
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
}
}
wac.setServletContext(getServletContext());
wac.setServletConfig(getServletConfig());
wac.setNamespace(getNamespace());
wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));
// The wac environment's #initPropertySources will be called in any case when the context
// is refreshed; do it eagerly here to ensure servlet property sources are in place for
// use in any post-processing or initialization that occurs below prior to #refresh
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
}
postProcessWebApplicationContext(wac);
applyInitializers(wac);
//這裏進行整合，具體的源碼就不看了
wac.refresh();
}
那麼DisapatcherServlet的初始化是如何進行的?SpringMVC中的組件是如何加載的？答案在initWebApplicationContext()中的onRefresh()方法中，該方法在其子類DispatcherServlet的onRefresh()方法中進行了重寫。而在onRefresh()方法中調用了initStrategies()方法來完成初始化工作，初始化Spring MVC的9個組件。
protected void onRefresh(ApplicationContext context) {
initStrategies(context);
}
initStrategies（）完成了對組件的初始化
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}
到這就完成了init()的初始化！真累啊。
2.執行過程
當一個get/post請求進來後，會執行sevlet的doPost/doGet方法。以post請求爲例。在DispatcherServlet中沒有找到，找其父類FrameWorkServlet，發現！
protected final void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
調用了processRequest()方法。
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 {
//執行請求
doService(request, response);
}
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);
}
}
查看doService（）具體實現在DispatcherServlet中
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(DEFAULT_STRATEGIES_PREFIX)) {
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 {
//重點看這！
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);
}
}
}
}
其中調用了doDispatch()。這個方法是流程中最重要的一個方法，幾乎所有的事情都在這個方法中調用了！
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
//創建一個處理器執行鏈對象
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
//創建ModelAndView對象
ModelAndView mv = null;
Exception dispatchException = null;
try {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
//通過request請求初始化HandlerExecutionChain對象
mappedHandler = getHandler(processedRequest);//重點關注這個方法
if (mappedHandler == null || mappedHandler.getHandler() == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
//根據handler選擇合適的HandlerAdapter
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()/*這個方法返回的是一個Object handler對象*/);
// 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.
//適配器處理handler後返回ModelAndView對象
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
//視圖對象的處理
applyDefaultViewName(processedRequest, mv);
//applyPostHandle（）該方法會獲得攔截器對象數組。HandlerInterceptor[] interceptors = getInterceptors();
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);
}
//處理最終結果 渲染視圖等 重點看這裏
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
......
}
doDispatch()做了很多事情，最主要的就是爲handler選擇相應的處理器適配器（HandlerAdapter）並且處理handler返回ModelAndView對象。最後會渲染視圖。
先查看其中的mappedHandler = getHandler()做了那些事情：
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;
}
創建了一個處理器映射器（HandlerMapping）對象hm，並且得到了一個處理器執行鏈（HandlerExecutionChain）對象,（該對象包含了攔截器對象（HandlerInterceptor）和handler對象）。在doDispatch()和下面的getHandler()會體現。
查看其中的hm.getHandler()具體做了那些事！該方法是HandlerMapping接口中的方法。具體實現類AbstractHandlerMapping實現了該方法。
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
//根據請求獲取相應的handler，重點看這裏
Object handler = getHandlerInternal(request);
if (handler == null) {
//沒有查找到就是用默認的Handler
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
//如果handler是字符串類型 說明是bean名稱 需要獲取handler bean對象
if (handler instanceof String) {
String handlerName = (String) handler;
handler = getApplicationContext().getBean(handlerName);
}
//這裏封裝執行鏈對象，重點看這裏
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;
}
首先具體查看getHandlerInternal()是如何通過request獲得handler對象。該方法在AbstractHandlerMapping的子類AbstractHandlerMethodMapping中有實現：
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
//獲取request中的url
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
if (logger.isDebugEnabled()) {
logger.debug("Looking up handler method for path " + lookupPath);
}
this.mappingRegistry.acquireReadLock();
try {
//根據request中的url來獲取HandlerMethod對象(實際就是handler，因爲最後返回的就是這個對象)
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
if (logger.isDebugEnabled()) {
if (handlerMethod != null) {
logger.debug("Returning handler method [" + handlerMethod + "]");
}
else {
logger.debug("Did not find handler method for [" + lookupPath + "]");
}
}
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
this.mappingRegistry.releaseReadLock();
}
}
查看lookupHandlerMethod()的具體實現；
// AbstractHandlerMethodMapping
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
//創建匹配集合
List<Match> matches = new ArrayList<>();
// 直接匹配
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
// 存在匹配 則添加到匹配集合中
if (directPathMatches != null) {
addMatchingMappings(directPathMatches, matches, request);
}
// 沒有匹配 遍歷所有處理方法查找
if (matches.isEmpty()) {
// No choice but to go through all mappings...
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
// 存在匹配
if (!matches.isEmpty()) {
Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
matches.sort(comparator);
if (logger.isTraceEnabled()) {
logger.trace("Found " + matches.size() + " matching mapping(s) for [" + lookupPath + "] : " + matches);
}
// 排序之後獲取第一個
Match bestMatch = matches.get(0);
// 有多個匹配 會找出第二個進行比較
if (matches.size() > 1) {
if (CorsUtils.isPreFlightRequest(request)) {
return PREFLIGHT_AMBIGUOUS_MATCH;
}
Match secondBestMatch = matches.get(1);
if (comparator.compare(bestMatch, secondBestMatch) == 0) {
Method m1 = bestMatch.handlerMethod.getMethod();
Method m2 = secondBestMatch.handlerMethod.getMethod();
throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" +
request.getRequestURL() + "': {" + m1 + ", " + m2 + "}");
}
}
// 設置request參數
handleMatch(bestMatch.mapping, lookupPath, request);
// 返回匹配的url處理方法
return bestMatch.handlerMethod;
}
else {
// 處理沒有匹配情況直接返回null
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
}
這樣成功匹配到handler對象，接下來在看getHandlerExecutionChain()是如何處理HandlerExecutionChain對象。AbstractHandlerMapping類中。
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
// 如果當前handler不是執行鏈類型 則創建一個新的執行鏈封裝
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
//當前url
String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
//遍歷攔截器 與當前url匹配的添加至執行鏈中
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
到這裏我們完成了HandlerExecutionHandler對象和其中的Handler對象以及HandlerInterrceptor攔截器對象的初始化，以及獲得相應的HandlerAdapter處理器適配器來處理handler對象，然後返回ModelAndView對象上面的都是在DispatcherServlet這個類的doDispatch（)方法中進行的！
現在我們還差渲染視圖這個工作，也是在doDispatch()中調用的processDispatchResult()該方法進行的。
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
@Nullable Exception exception) throws Exception {
boolean errorView = false;
if (exception != null) {
if (exception instanceof ModelAndViewDefiningException) {
logger.debug("ModelAndViewDefiningException encountered", exception);
mv = ((ModelAndViewDefiningException) exception).getModelAndView();
}
else {
Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
mv = processHandlerException(request, response, handler, exception);
errorView = (mv != null);
}
}
// Did the handler return a view to render?
if (mv != null && !mv.wasCleared()) {
// 渲染
render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +
"': assuming HandlerAdapter completed request handling");
}
}
if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Concurrent handling started during a forward
return;
}
if (mappedHandler != null) {
mappedHandler.triggerAfterCompletion(request, response, null);
}
}
看render()方法。
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Determine locale for request and apply it to the response.
// 設置本地化
Locale locale =
(this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale());
response.setLocale(locale);
View view;
String viewName = mv.getViewName();
if (viewName != null) {
// We need to resolve the view name.
// 解析視圖名獲取視圖對象
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 {
// No need to lookup: the ModelAndView object contains the actual View object.
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.isDebugEnabled()) {
logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'");
}
try {
if (mv.getStatus() != null) {
response.setStatus(mv.getStatus().value());
}
// 委託給視圖進行渲染
view.render(mv.getModelInternal(), request, response);
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name '" +
getServletName() + "'", ex);
}
throw ex;
}
}
到這DispatcherServlet的執行流程基本就結束了。
最後附上基本流程圖：
參考：https://blog.csdn.net/qq_38410730/article/details/79426673
https://blog.csdn.net/laravelshao/article/details/82763436