spring mvc 的启动过程

<web-app>

<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/app-context.xml</param-value>
</context-param>

<servlet>
<servlet-name>app</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value></param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>app</servlet-name>
<url-pattern>/app/*</url-pattern>
</servlet-mapping>

</web-app>

org.springframework.web.context.ContextLoaderListener

初始化方法

public void contextInitialized(ServletContextEvent event) {
super.contextInitialized(event);
}

找其父类

public void contextInitialized(ServletContextEvent event) {
this.initWebApplicationContext(event.getServletContext());
}

进入initWebApplicationContext方法

if(this.context == null) {
this.context = this.createWebApplicationContext(servletContext);//创建WebApplicationContext
}

if(this.context instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext err = (ConfigurableWebApplicationContext)this.context;
if(!err.isActive()) {
if(err.getParent() == null) {
ApplicationContext elapsedTime = this.loadParentContext(servletContext);
err.setParent(elapsedTime);
}

this.configureAndRefreshWebApplicationContext(err, servletContext);
}
}

servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);

把WebApplicationContext放到servletContext

这边的上下文为Root WebApplicationContext包括serviceImpl，daoImpl

public abstract class AbstractContextLoaderInitializer implements WebApplicationInitializer

public abstract class AbstractDispatcherServletInitializer extends AbstractContextLoaderInitializer

public abstract class AbstractAnnotationConfigDispatcherServletInitializer extends AbstractDispatcherServletInitializer

public class AnnotationConfigWebApplicationContext extends AbstractRefreshableWebApplicationContext

public abstract class AbstractDispatcherServletInitializer extends AbstractContextLoaderInitializer {

public void onStartup(ServletContext servletContext) throws ServletException {super.onStartup(servletContext);this.registerDispatcherServlet(servletContext);}protected void registerDispatcherServlet(ServletContext servletContext) {String servletName = this.getServletName();Assert.hasLength(servletName, "getServletName() may not return empty or null");WebApplicationContext servletAppContext = this.createServletApplicationContext();//创建servletApplicationContextAssert.notNull(servletAppContext, "createServletApplicationContext() did not return an application context for servlet [" + servletName + "]");DispatcherServlet dispatcherServlet = new DispatcherServlet(servletAppContext);Dynamic registration = servletContext.addServlet(servletName, dispatcherServlet);//把 dispatcherServlet放到servletContext里面Assert.notNull(registration, "Failed to register servlet with name \'" + servletName + "\'." + "Check if there is another servlet registered under the same name.");registration.setLoadOnStartup(1);registration.addMapping(this.getServletMappings());registration.setAsyncSupported(this.isAsyncSupported());Filter[] filters = this.getServletFilters();if(!ObjectUtils.isEmpty(filters)) {Filter[] var7 = filters;int var8 = filters.length;for(int var9 = 0; var9 < var8; ++var9) {Filter filter = var7[var9];this.registerServletFilter(servletContext, filter);}}this.customizeRegistration(registration);}

protected WebApplicationContext createServletApplicationContext() {//初始化servletApplicationContext上下文AnnotationConfigWebApplicationContext servletAppContext = new AnnotationConfigWebApplicationContext();Class[] configClasses = this.getServletConfigClasses();if(!ObjectUtils.isEmpty(configClasses)) {servletAppContext.register(configClasses);}return servletAppContext;}

public class AnnotationConfigWebApplicationContext extends AbstractRefreshableWebApplicationContext

这边的上下文为servlet的上下文，即controller的上下文

第三步，DispatcherServlet请求处理

public class DispatcherServlet extends FrameworkServlet

{

protected void initStrategies(ApplicationContext context) {//把上下文的数据初始化对象中this.initMultipartResolver(context);this.initLocaleResolver(context);this.initThemeResolver(context);this.initHandlerMappings(context);this.initHandlerAdapters(context);this.initHandlerExceptionResolvers(context);this.initRequestToViewNameTranslator(context);this.initViewResolvers(context);this.initFlashMapManager(context);}

protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {if(this.logger.isDebugEnabled()) {String attributesSnapshot = urlPathHelper.getRequestUri(request);String inputFlashMap = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult()?" resumed":"";this.logger.debug("DispatcherServlet with name \'" + this.getServletName() + "\'" + inputFlashMap + " processing " + request.getMethod() + " request for [" + attributesSnapshot + "]");}HashMap attributesSnapshot1 = null;if(WebUtils.isIncludeRequest(request)) {this.logger.debug("Taking snapshot of request attributes before include");attributesSnapshot1 = new HashMap();Enumeration inputFlashMap1 = request.getAttributeNames();label113:while(true) {String attrName;do {if(!inputFlashMap1.hasMoreElements()) {break label113;}attrName = (String)inputFlashMap1.nextElement();} while(!this.cleanupAfterInclude && !attrName.startsWith("org.springframework.web.servlet"));attributesSnapshot1.put(attrName, request.getAttribute(attrName));}}request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.getWebApplicationContext());request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);request.setAttribute(THEME_SOURCE_ATTRIBUTE, this.getThemeSource());FlashMap inputFlashMap2 = this.flashMapManager.retrieveAndUpdate(request, response);if(inputFlashMap2 != null) {request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap2));}request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);try {this.doDispatch(request, response);} finally {if(WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {return;}if(attributesSnapshot1 != null) {this.restoreAttributesAfterInclude(request, attributesSnapshot1);}}}protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {HttpServletRequest processedRequest = request;HandlerExecutionChain mappedHandler = null;boolean multipartRequestParsed = false;WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);try {try {ModelAndView err = null;Exception dispatchException = null;try {processedRequest = this.checkMultipart(request);multipartRequestParsed = processedRequest != request;mappedHandler = this.getHandler(processedRequest); //根据条件找到自己mappedHandlerif(mappedHandler == null || mappedHandler.getHandler() == null) {this.noHandlerFound(processedRequest, response);return;}HandlerAdapter ex = this.getHandlerAdapter(mappedHandler.getHandler());//获取HandlerAdapterString method = request.getMethod();boolean isGet = "GET".equals(method);if(isGet || "HEAD".equals(method)) {long lastModified = ex.getLastModified(request, mappedHandler.getHandler());if(this.logger.isDebugEnabled()) {String requestUri = urlPathHelper.getRequestUri(request);this.logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);}if((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {return;}}if(!mappedHandler.applyPreHandle(processedRequest, response)) {return;}try {err = ex.handle(processedRequest, response, mappedHandler.getHandler());} finally {if(asyncManager.isConcurrentHandlingStarted()) {return;}}this.applyDefaultViewName(request, err);//获取viewNamemappedHandler.applyPostHandle(processedRequest, response, err);} catch (Exception var28) {dispatchException = var28;}this.processDispatchResult(processedRequest, response, mappedHandler, err, dispatchException);} catch (Exception var29) {this.triggerAfterCompletion(processedRequest, response, mappedHandler, var29);} catch (Error var30) {this.triggerAfterCompletionWithError(processedRequest, response, mappedHandler, var30);}} finally {if(asyncManager.isConcurrentHandlingStarted()) {mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);return;} else {if(multipartRequestParsed) {this.cleanupMultipart(processedRequest);}}}}