8.1。 SpringBoot启动流程--把spring应用跑起来

创建IOC容器 createApplicationContext()

protected ConfigurableApplicationContext createApplicationContext() {
        return this.applicationContextFactory.create(this.webApplicationType);
    }
=============根据当前的应用类型（Servlet）创建容器
//当前会创建AnnotationConfigServletWebServerApplicationContext
ApplicationContextFactory DEFAULT = (webApplicationType) -> {
        try {
            switch (webApplicationType) {
            case SERVLET:
                return new AnnotationConfigServletWebServerApplicationContext();
            case REACTIVE:
                return new AnnotationConfigReactiveWebServerApplicationContext();
            default:
                return new AnnotationConfigApplicationContext();
            }
        }
        catch (Exception ex) {
            throw new IllegalStateException("Unable create a default ApplicationContext instance, "
                    + "you may need a custom ApplicationContextFactory", ex);
        }
    };

准备ApplicationContext IOC容器的基本信息 prepareContext()

private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context,
            ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
            ApplicationArguments applicationArguments, Banner printedBanner) {
        //保存前面的基础环境
        context.setEnvironment(environment);
        //IOC容器的后置处理流程。
        postProcessApplicationContext(context);
        //应用初始化器：applyInitializers
        applyInitializers(context);
        //遍历所有的 listener 调用 contextPrepared
        //ioc容器的环境准备就绪了(contextPrepared方法的源码在下面)
        listeners.contextPrepared(context);
        //引导上下文的环境关闭了
        bootstrapContext.close(context);
        if (this.logStartupInfo) {
            logStartupInfo(context.getParent() == null);
            logStartupProfileInfo(context);
        }
        // Add boot specific singleton beans
        //拿到bean工厂
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        //注册单实例
        beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
        //打印banner
        if (printedBanner != null) {
            beanFactory.registerSingleton("springBootBanner", printedBanner);
        }
        if (beanFactory instanceof DefaultListableBeanFactory) {
            ((DefaultListableBeanFactory) beanFactory)
                    .setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
        }
        if (this.lazyInitialization) {
            context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
        }
        // Load the sources
        Set