8.2、SpringBoot启动流程--把spring应用跑起来（接8.1）

=================进入getOrCreateEnvironment()
private ConfigurableEnvironment getOrCreateEnvironment() {
        if (this.environment != null) {
            return this.environment;
        }
        switch (this.webApplicationType) {
        case SERVLET: //如果是原生servlet编程
            return new StandardServletEnvironment();
        case REACTIVE: //如果是响应式编程
            return new StandardReactiveWebEnvironment();
        default:
            return new StandardEnvironment();
        }
    }


====================进入configureEnvironment()
protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) {
        //给环境添加一些类型转换器
        if (this.addConversionService) {
            ConversionService conversionService = ApplicationConversionService.getSharedInstance();
            environment.setConversionService((ConfigurableConversionService) conversionService);
        }
        //加载(读取)外部配置源
        //即读取所有的配置源的配置属性值
        configurePropertySources(environment, args);
        //激活Profiles环境
        configureProfiles(environment, args);
    }
==========进入configurePropertySources()
protected void configurePropertySources(ConfigurableEnvironment environment, String[] args) {
        //获取到所有配置源
        MutablePropertySources sources = environment.getPropertySources();
        DefaultPropertiesPropertySource.ifNotEmpty(this.defaultProperties, sources::addLast);
        //命令行信息
        if (this.addCommandLineProperties && args.length > 0) {
            String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;
            if (sources.contains(name)) {
                PropertySource source = sources.get(name);
                CompositePropertySource composite = new CompositePropertySource(name);
                composite.addPropertySource(
                        new SimpleCommandLinePropertySource("springApplicationCommandLineArgs", args));
                composite.addPropertySource(source);
                sources.replace(name, composite);
            }
            else {
                sources.addFirst(new SimpleCommandLinePropertySource(args));
            }
        }
    }

==============进入environmentPrepared（）
void environmentPrepared(ConfigurableBootstrapContext bootstrapContext, ConfigurableEnvironment environment) {
        doWithListeners("spring.boot.application.environment-prepared",
                (listener) -> listener.environmentPrepared(bootstrapContext, environment));
    }

所有配置源

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);
        listeners.contextPrepared(context);
        bootstrapContext.close(context);
        if (this.logStartupInfo) {
            logStartupInfo(context.getParent() == null);
            logStartupProfileInfo(context);
        }
        // Add boot specific singleton beans
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
        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