SpringMvc中DispatcherServlet的init方法阅读

Web容器构造DispatcherServlet完成之后，调用Servlet的init方法

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

这个方法将Web容器传入的ServletConfig赋予config属性，并调用子类HttpServletBean的init方法.

	@Override
	public final void init() throws ServletException {
		...
		// Set bean properties from init parameters.
		//通过servletConfig对象获取初始化参数，并封装成一个PropertyValue,并对必要的属性进行校验，如果没有则抛出异常
			PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);//bw可以反射的方式对this进行属性赋值
			ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
			initBeanWrapper(bw);
			bw.setPropertyValues(pvs, true);//对传入的bean进行属性赋值
                ...
 // Let subclasses do whatever initialization they like.
		initServletBean();
	}

子类FrameworkServlet对initServletBean方法进行实现，主要是初始化servlet的WebApplicationContext;

		try {
			this.webApplicationContext = initWebApplicationContext();
			initFrameworkServlet();
		}

	protected WebApplicationContext initWebApplicationContext() {
		WebApplicationContext rootContext =//获取Spring在ServletContext中存放的WebApplicationContext
				WebApplicationContextUtils.getWebApplicationContext(getServletContext());
		WebApplicationContext wac = null;
                ...//判定为null,不走省略掉的代码
		if (wac == null) {
			wac = findWebApplicationContext();//没有获取到，为空
		}
		if (wac == null) {
			// No context instance is defined for this servlet -> create a local one
			wac = createWebApplicationContext(rootContext);//真正创建属于Servlet的WebApplicationContext
		}

		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.
            //这里会触发DispatcherServlet的onRefresh方法，对Servlet进行初始化操作。
			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;
	}

创建一个全新的WebApplicationContext;

	protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
		Class<?> contextClass = getContextClass();//获取默认的ContextClass,还是XmlWebApplicationContext
                ...//判定....
		ConfigurableWebApplicationContext wac =
				(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

		wac.setEnvironment(getEnvironment());
		wac.setParent(parent);//将Spring的webApplicationContext作为它的父。
		wac.setConfigLocation(getContextConfigLocation());

		configureAndRefreshWebApplicationContext(wac);//根据wac的配置进行refresh操作。

		return wac;
	}

执行完后回到最初的方法中，接着调用initFrameworkServlet，这个方法并没有被DispatcherServlet实现。