Spring源码解析（十一）整合SpringMVC

tomcat找到我们应用中的默认sping-web包下/meta- INF/service/javax.servlet.ServletContainerInitializer

在调用SpringServletContainerInitializer.onStartUp() 之前会找到所有实现了WebApplicationInitializer的类，传入到OnStartup的 webAppInitializerClasses参数中，并传入Servlet上下文对象

org.springframework.web.SpringServletContainerInitializer#onStartup

	@Override
	public void onStartup(@Nullable Set> webAppInitializerClasses, ServletContext servletContext)
			throws ServletException {

		List initializers = Collections.emptyList();

		if (webAppInitializerClasses != null) {
			initializers = new ArrayList<>(webAppInitializerClasses.size());
			for (Class waiClass : webAppInitializerClasses) {
				// 接口和抽象类servlet容器也会给我们，但是我们不要
				// 排除接口和容器
				if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) &&
						WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
					try {
						// 实例化，然后添加到集合中
						initializers.add((WebApplicationInitializer)
								ReflectionUtils.accessibleConstructor(waiClass).newInstance());
					}
					catch (Throwable ex) {
						throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex);
					}
				}
			}
		}

		if (initializers.isEmpty()) {
			servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
			return;
		}

		servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
		AnnotationAwareOrderComparator.sort(initializers);
		// 调用initializer.onStartup  进行扩展
		for (WebApplicationInitializer initializer : initializers) {
			initializer.onStartup(servletContext);
		}
	}

org.springframework.web.servlet.support.AbstractDispatcherServletInitializer#onStartup

@Override
	public void onStartup(ServletContext servletContext) throws ServletException {
		//registerContextLoaderListener  ok
		super.onStartup(servletContext);
		// registerDispatcherServlet
		registerDispatcherServlet(servletContext);
	}

	
	protected void registerContextLoaderListener(ServletContext servletContext) {
		// 创建父容器 ，
		WebApplicationContext rootAppContext = createRootApplicationContext();
		if (rootAppContext != null) {
			ContextLoaderListener listener = new ContextLoaderListener(rootAppContext);
			// 设置初始化器
			listener.setContextInitializers(getRootApplicationContextInitializers());
			servletContext.addListener(listener);
		}
		else {
			logger.debug("No ContextLoaderListener registered, as " +
					"createRootApplicationContext() did not return an application context");
		}
	}

org.springframework.web.servlet.support.AbstractDispatcherServletInitializer#registerDispatcherServlet

protected void registerDispatcherServlet(ServletContext servletContext) {
		String servletName = getServletName();
		Assert.hasLength(servletName, "getServletName() must not return null or empty");
		// 创建子容器
		WebApplicationContext servletAppContext = createServletApplicationContext();
		Assert.notNull(servletAppContext, "createServletApplicationContext() must not return null");
		// 创建DispatcherServlet
		frameworkServlet dispatcherServlet = createDispatcherServlet(servletAppContext);
		Assert.notNull(dispatcherServlet, "createDispatcherServlet(WebApplicationContext) must not return null");
		// 初始化器
		dispatcherServlet.setContextInitializers(getServletApplicationContextInitializers());

		ServletRegistration.Dynamic registration = servletContext.addServlet(servletName, dispatcherServlet);
		if (registration == null) {
			throw new IllegalStateException("Failed to register servlet with name '" + servletName + "'. " +
					"Check if there is another servlet registered under the same name.");
		}
		// 启动时加载
		registration.setLoadonStartup(1);
		// 映射
		registration.addMapping(getServletMappings());
		// 是否异步支持
		registration.setAsyncSupported(isAsyncSupported());
		// 设置DispatcherServlet的过滤器
		Filter[] filters = getServletFilters();
		if (!ObjectUtils.isEmpty(filters)) {
			for (Filter filter : filters) {
				registerServletFilter(servletContext, filter);
			}
		}
		// 空方法， 可以再对DispatcherServlet进行定制
		customizeRegistration(registration);
	}

外置tomcat会帮我们调用ContextLoaderListener#contextInitialized 进行初始化；

前面只是创建Spring容器，此处调用configureAndRefreshWebApplicationContext()方法从而调用refresh()方法

protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
		if (ObjectUtils.identityToString(wac).equals(wac.getId())) {

			// 设置id
			String idParam = sc.getInitParameter(CONTEXT_ID_PARAM);
			if (idParam != null) {
				wac.setId(idParam);
			}
			else {
				// Generate default id...
				wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
						ObjectUtils.getDisplayString(sc.getContextPath()));
			}
		}
		// 设置ServletContext到spring上下文
		wac.setServletContext(sc);
		// 获得servlet容器中的全局参数contextConfigLocation  （xml）
		String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
		if (configLocationParam != null) {
			wac.setConfigLocation(configLocationParam);
		}

		// 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) {
			((ConfigurableWebEnvironment) env).initPropertySources(sc, null);
		}
		// 在容器加载前 可以通过设置初始化参数contextInitializerClasses、globalInitializerClasses 进行扩展
		customizeContext(sc, wac);
		// 刷新容器
		wac.refresh();
	}

外置tomcat会帮我们调用DispatcherServlet#init()

最终调用org.springframework.web.servlet.frameworkServlet#initWebApplicationContext

	protected WebApplicationContext initWebApplicationContext() {
		// 获得ContextLoaderListener存的父容器
		WebApplicationContext rootContext =
				WebApplicationContextUtils.getWebApplicationContext(getServletContext());
		WebApplicationContext wac = null;

		if (this.webApplicationContext != null) {
			// 获得子容器
			wac = this.webApplicationContext;
			if (wac instanceof ConfigurableWebApplicationContext) {
				ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
				if (!cwac.isActive()) {
					// 如果没有设置父容器   spring  doGetBean
					if (cwac.getParent() == null) {
						cwac.setParent(rootContext);
					}
					// 配置并且加载子容器
					configureAndRefreshWebApplicationContext(cwac);
				}
			}
		}
		if (wac == null) {
			// 从servlet上下文根据名字从域里面获取
			wac = findWebApplicationContext();
		}
		if (wac == null) {
			// xml会在这里创建
			wac = createWebApplicationContext(rootContext);
		}

		//refreshEventReceived 它会在容器加载完设置为true (通过事件onApplicationEvent)
		// springboot在这初始化组件
		if (!this.refreshEventReceived) {
			synchronized (this.onRefreshMonitor) {
				onRefresh(wac);
			}
		}

		if (this.publishContext) {
			// 将当前容器放到servlet域中， 可以再创建子容器
			String attrName = getServletContextAttributeName();
			getServletContext().setAttribute(attrName, wac);
		}

		return wac;
	}

并且监听子容器的ContextRefreshListener  去初始化SpringMvc的组件

org.springframework.web.servlet.DispatcherServlet#initStrategies

	protected void initStrategies(ApplicationContext context) {
		initMultipartResolver(context);
		initLocaleResolver(context);
		initThemeResolver(context);
		initHandlerMappings(context);
		initHandlerAdapters(context);
		initHandlerExceptionResolvers(context);
		initRequestToViewNameTranslator(context);
		initViewResolvers(context);
		initFlashMapManager(context);
	}

tomcat 的流程，后续补充...

欢迎跟帖：caicongyang_CSDN博客-Java基础,sshm,Hadoop/spark领域博主