ServletWebServerApplicationContext.java
创建一个容器，在run()方法中被调用。比如调用onRefresh()，把ServletWebServerApplicationContext注册到ServletContext属性中,并调用ServletContextInitializer启动tomcat容器。
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {...}
beanFactory.addBeanPostProcessor(new WebApplicationContextServletContextAwareProcessor(this));
添加WebApplicationContextServletContextAwareProcessor这个BeanPostProcessor，是为了实现ServletContextAware接口的类能获得ServletContext
protected void onRefresh() {...}
createWebServer()
调用createWebServer(),详解如下
-createWebServer() {...}
getSelfInitializer().onStartup(servletContext);
调用selfInitialize（），把Spring容器（当前实例）注入ServletContext，ServletContextInitializer-》启动容器
-private void selfInitialize(ServletContext servletContext) throws ServletException {...}
prepareWebApplicationContext(servletContext);
// <1> 添加 Spring 容器到 servletContext 属性中。
registerApplicationScope(servletContext);
// <2> 注册 ServletContextScope
WebApplicationContextUtils.registerEnvironmentBeans(getBeanFactory(), servletContext);
// <3> 注册 web-specific environment beans ("contextParameters", "contextAttributes")
for (ServletContextInitializer beans : getServletContextInitializerBeans()) {...}
beans.onStartup(servletContext);
// <4> 获得所有 ServletContextInitializer ，并逐个进行启动
-protected void prepareWebApplicationContext(ServletContext servletContext) {...}
Object rootContext = servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
获取根容器
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this);
如果rootContext为空，则把容器设置到servletContext中。
-finishRefresh(){...}
super.finishRefresh();
WebServer webServer = startWebServer();
启动WebServer
publishEvent(new ServletWebServerInitializedEvent(webServer, this));
如果WebServer启动成功，则发布ServletWebServerInitializedEvent事件
-private WebServer startWebServer() {...}
webServer.start();
启动webServer
TomcatServer
-public void start() throws WebServerException {...}
启动tomcat容器
Connector connector = this.tomcat.getConnector();
performDeferredLoadOnStartup();
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带有*WebxxxApplication的容器。会创建创建SpringMVC