springmvc的初始化

先从核心DispatcherServlet入手：
  既然是servlet那我们先来看serlvet的初始化：
    @Override
	public final void init() throws ServletException {
		if (logger.isDebugEnabled()) {
			logger.debug("Initializing servlet '" + getServletName() + "'");
		}

		// Set bean properties from init parameters.
		try {   //初始化一些数据
			PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
			//装饰DispatcherServlet对象
			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
			//初始化资源加载器
			//初始化BeanWrapper
			ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
			initBeanWrapper(bw);
			bw.setPropertyValues(pvs, true);
		}
		catch (BeansException ex) {
			logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
			throw ex;
		}

		// Let subclasses do whatever initialization they like.
		//初始化
		initServletBean();

		if (logger.isDebugEnabled()) {
			logger.debug("Servlet '" + getServletName() + "' configured successfully");
		}
	}


     protected final void initServletBean() throws ServletException {
		getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
		if (this.logger.isInfoEnabled()) {
			this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
		}
		long startTime = System.currentTimeMillis();

		try {  
		        //初始化webApplicationContext
			this.webApplicationContext = initWebApplicationContext();
			//空方法没实现
			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;
		}

		if (this.logger.isInfoEnabled()) {
			long elapsedTime = System.currentTimeMillis() - startTime;
			this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
					elapsedTime + " ms");
		}
	}


     protected WebApplicationContext initWebApplicationContext() {
                //获取spring初始的ApplicationContext
		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
			//创建WebApplicationContext，这里也和spring一样走的AbstractApplicationContext的refresh方法初始化
			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;
	}


//这里要提一句springmvc组件的初始化是在DisPatcher的initStrategies方法，
 protected void initStrategies(ApplicationContext context) {
		initMultipartResolver(context);
		initLocaleResolver(context);
		initThemeResolver(context);
		initHandlerMappings(context);
		initHandlerAdapters(context);
		initHandlerExceptionResolvers(context);
		initRequestToViewNameTranslator(context);
		initViewResolvers(context);
		initFlashMapManager(context);
	}
//springmvc会将组件的初始化工作放在ContextRefreshListener中。这是一个内部类，然后就走spring的初始化流程最后在AbstractApplicationContext的finishRefresh方法进行初始化。
private class ContextRefreshListener implements ApplicationListener<ContextRefreshedEvent> {

		public void onApplicationEvent(ContextRefreshedEvent event) {
			FrameworkServlet.this.onApplicationEvent(event);
		}
	}

//总结:其实和spring的初始化过程一样，spring是初始化ApplicationContext。这里是初始化
//WebApplicationContext。装的bean也不一样。springmvc扫描的是controller。

//其实DispatcherServlet的初始化就是初始化WebApplicationContext和他自身的一些组件。