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先来上一张类的结构图：

图里只画了跟初始化相关的方法。

首先DispatcherServlet也是一个Servlet，初始化从init()方法开始。

下面就具体看看ini()是怎么实现的吧。

1.Servlet 是个接口；

public void init(ServletConfig config) throws ServletException;

2.GenericServlet 中实现了初始化方法。

public void init(ServletConfig config) throws ServletException {	this.config = config;	this.init();    }

这里调用了一个没有参数的init()；是个空方法；

public void init() throws ServletException {    }

3.HttpServlet 没有对初始化相关的方法进行覆盖。

4.HttpServletBean，重写了init()方法。

@Override	public final void init() throws ServletException {		if (logger.isDebugEnabled()) {			logger.debug("Initializing servlet '" + getServletName() + "'");		}		// Set bean properties from init parameters.		try {			PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);			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.		initServletBean();		if (logger.isDebugEnabled()) {			logger.debug("Servlet '" + getServletName() + "' configured successfully");		}	}

其中又掉了一个initServletBean()；方法，这本类中也是个空实现。

protected void initServletBean() throws ServletException {	}

5.FrameworkServlet 果不其然的重写了上边留空的方法：initServletBean();

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

在这个方法中最重要的就是调用了一个initWebApplicationContext() 方法。

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;	}

一系列的赋值和判断，最关键的，跟初始化相关的，就是调用了onRefresh(),同样的套路，这个方法在本类中为空实现，留给子类去实现。

6.终于到了DispatcherServlet，找到onRefresh()，简单！调用initStrategies(ApplicationContext context);这个方法就在下边，这下清楚了，一堆的初始化方法。具体代码就不粘了。

/**	 * This implementation calls {@link #initStrategies}.	 */	@Override	protected void onRefresh(ApplicationContext context) {		initStrategies(context);	}	/**	 * Initialize the strategy objects that this servlet uses.	 * 
May be overridden in subclasses in order to initialize further strategy objects.	 */	protected void initStrategies(ApplicationContext context) {		initMultipartResolver(context);		initLocaleResolver(context);		initThemeResolver(context);		initHandlerMappings(context);		initHandlerAdapters(context);		initHandlerExceptionResolvers(context);		initRequestToViewNameTranslator(context);		initViewResolvers(context);		initFlashMapManager(context);	}

到这里整个加载过程就理清楚了。