SpringMvc中容器加载的过程源码详解

<!-- Spring监听器 -->
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:/config/beans.xml</param-value>
	</context-param>

	<!-- Spring MVC servlet -->
	<servlet>
		<servlet-name>SpringMVC</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>classpath:spring-mvc.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
		<async-supported>true</async-supported>
	</servlet>
	<servlet-mapping>
		<servlet-name>SpringMVC</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>

@Override
	public final void init() throws ServletException {
		if (logger.isDebugEnabled()) {
			logger.debug("Initializing servlet '" + getServletName() + "'");
		}

		// Set bean properties from init parameters.
		// 对Servlet初始化参数封装成PropertyValues对象
		PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
		if (!pvs.isEmpty()) {
			try {
				//将serlvet封装为BeanWrapper对象
				BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
				// 资源加载器
				ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
				// 设置一个属性编辑器
				bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
				// 执行init,(留给子类覆盖的,dispatcherServlet都没有覆盖方法,所以是空的)
				initBeanWrapper(bw);
				//设置配置
				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.
		// 初始化serlvetBean了
		initServletBean();

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

protected WebApplicationContext initWebApplicationContext() {
		//获取web.xml配置的spring容器
		WebApplicationContext rootContext =
				WebApplicationContextUtils.getWebApplicationContext(getServletContext());
		WebApplicationContext wac = null;

		// web容器,一般开始为空;springboot项目则不为空;
		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);
				}
			}
		}
		// 为空就查找,查找已经绑定的上下文,一般也是空
		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();
		}
		// 根据父容器,创建web容器,就是子容器,这里面子容器进行了刷新
		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.
			// 刷新上下文,这里主要加载dispatcherservlet的组件
			onRefresh(wac);
		}

		if (this.publishContext) {
			// Publish the context as a servlet context attribute.
			// 将web容器作为servlet上下文属性进行发布
			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;
	}

protected WebApplicationContext createWebApplicationContext(WebApplicationContext parent) {
		return createWebApplicationContext((ApplicationContext) parent);
	}
protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
		// 获取web容器的类型
		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");
		}
		// 反射创建web容器
		ConfigurableWebApplicationContext wac =
				(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
		// 设置环境
		wac.setEnvironment(getEnvironment());
		// 设置父容器
		wac.setParent(parent);
		//设置配置文件地址
		wac.setConfigLocation(getContextConfigLocation());
		// 加载配置,刷新容器
		configureAndRefreshWebApplicationContext(wac);
		return wac;
	}

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());
			}
		}
		// 设置web容器所属的servletcontext
		wac.setServletContext(getServletContext());
		// 设置servletconfig
		wac.setServletConfig(getServletConfig());
		// 设置命名空间
		wac.setNamespace(getNamespace());
		// 设置监听器
		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) {
			// 刷新之前初始化一些属性资源
			((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
		}
		// web容器的钩子方法,跟spring容器的BeanPostProcess差不多
		postProcessWebApplicationContext(wac);
		// 添加一些初始化器,如果没有设置就没有
		applyInitializers(wac);
		// 刷新容器就是走的spring容器刷新
		wac.refresh();
	}

@Override
	protected void onRefresh(ApplicationContext context) {
		//初始化九大组件
		initStrategies(context);
	}
protected void initStrategies(ApplicationContext context) {
		// 初始化文件上传解析器
		initMultipartResolver(context);
		// 本地化解析
		initLocaleResolver(context);
		// 主题解析器
		initThemeResolver(context);
		// 处理器映射器 保存Url映射关系
		initHandlerMappings(context);
		// 处理器适配器
		initHandlerAdapters(context);
		// 异常解析器
		initHandlerExceptionResolvers(context);
		// 视图提取器，从request中获取viemName
		initRequestToViewNameTranslator(context);
		// 视图解析器
		initViewResolvers(context);
		// 参数解析器
		initFlashMapManager(context);
	}