/*
SpringApplication
*/

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//构造器初始化
public SpringApplication(ResourceLoader resourceLoader, Class... primarySources) {
this.sources = new LinkedHashSet();
//横幅模式 OFF,CONSOLE,LOG;
this.bannerMode = Mode.CONSOLE;
this.logStartupInfo = true;
this.addCommandLineProperties = true;
this.addConversionService = true;
this.headless = true;
this.registerShutdownHook = true;
this.additionalProfiles = new HashSet();
this.isCustomEnvironment = false;
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet(Arrays.asList(primarySources));
//应用类型NONE,SERVLET,REACTIVE;存在DispatcherHandler，不存在DispatcherServlet，ServletContainer，则为REACTIVE
//不存在javax.servlet.Servlet", "org.springframework.web.context.ConfigurableWebApplicationContext，则为NONE，则为SERVLET
this.webApplicationType = WebApplicationType.deduceFromClasspath();
//spring.factories文件中org.springframework.context.ApplicationContextInitializer=\
//org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
//org.springframework.boot.context.ContextIdApplicationContextInitializer,\
//org.springframework.boot.context.config.DelegatingApplicationContextInitializer,\
//org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer
this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
//org.springframework.context.ApplicationListener=\
//org.springframework.boot.ClearCachesApplicationListener,\
//org.springframework.boot.builder.ParentContextCloserApplicationListener,\
//org.springframework.boot.context.FileEncodingApplicationListener,\
//org.springframework.boot.context.config.AnsiOutputApplicationListener,\
//org.springframework.boot.context.config.ConfigFileApplicationListener,\
//org.springframework.boot.context.config.DelegatingApplicationListener,\
//org.springframework.boot.context.logging.ClasspathLoggingApplicationListener,\
//org.springframework.boot.context.logging.LoggingApplicationListener,\
//org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener 进行初始化
this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));
//推论出主类main
this.mainApplicationClass = this.deduceMainApplicationClass();
}
//核心开始运行
public ConfigurableApplicationContext run(String... args) {
//秒表，用于记录启动时间，记录每个任务 的时间，
StopWatch stopWatch = new StopWatch();
stopWatch.start();
//spring应用上下文，spring容器
ConfigurableApplicationContext context = null;
//自定义SpringApplication启动错误的回调接口
Collection exceptionReporters = new ArrayList();
//java.awt.headless模式 默认为true开启
this.configureHeadlessProperty();
//开启监听
//org.springframework.boot.SpringApplicationRunListener=\
//org.springframework.boot.context.event.EventPublishingRunListener
SpringApplicationRunListeners listeners = this.getRunListeners(args);
//
listeners.starting();

    Collection exceptionReporters;
    try {
        //参数封装，在命令行下启动应用带的参数，如--server.port
        ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
        //环境准备 1.加载外部化配置的资源到environment 2.触发ApplicationEnvironmentPreparedEvent事件
        ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
        //配置系统属性spring.beaninfo.ignore
        this.configureIgnoreBeanInfo(environment);
        //打印横幅
        Banner printedBanner = this.printBanner(environment);
        //创建ApplicationContext 根据webApplicationType
        //SERVLET:
        //        contextClass = Class.forName("org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext");
        //REACTIVE:
        //        contextClass = Class.forName("org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext");
        //    default:
        //        contextClass = Class.forName("org.springframework.context.annotation.AnnotationConfigApplicationContext");
        /**
        *AnnotationConfigServletWebServerApplicationContext层级关系-》ServletWebServerApplicationContext-》GenericWebApplicationContext
        *-》GenericApplicationContext-》AbstractApplicationContext
        */
        //部分属性：reader、scanner、beanFactory进行了实例化
        context = this.createApplicationContext();
        //实例化 用来支持报告关于启动的错误
        //# Error Reporters
        //org.springframework.boot.SpringBootExceptionReporter=\
        //org.springframework.boot.diagnostics.FailureAnalyzers
        exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
        //ApplicationContext准备 加载
        this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
        //核心：
        this.refreshContext(context);
        this.afterRefresh(context, applicationArguments);
        stopWatch.stop();
        if (this.logStartupInfo) {
            (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
        }

        listeners.started(context);
        this.callRunners(context, applicationArguments);
    } catch (Throwable var10) {
        this.handleRunFailure(context, var10, exceptionReporters, listeners);
        throw new IllegalStateException(var10);
    }

    try {
        listeners.running(context);
        return context;
    } catch (Throwable var9) {
        this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);
        throw new IllegalStateException(var9);
    }
}

//环境准备
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) {
//创建环境 SERVLET StandardServletEnvironment； REACTIVE StandardReactiveWebEnvironment； StandardEnvironment
ConfigurableEnvironment environment = this.getOrCreateEnvironment();
this.configureEnvironment((ConfigurableEnvironment)environment, applicationArguments.getSourceArgs());
listeners.environmentPrepared((ConfigurableEnvironment)environment);
this.bindToSpringApplication((ConfigurableEnvironment)environment);
if (!this.isCustomEnvironment) {
environment = (new EnvironmentConverter(this.getClassLoader())).convertEnvironmentIfNecessary((ConfigurableEnvironment)environment, this.deduceEnvironmentClass());
}

    ConfigurationPropertySources.attach((Environment)environment);
    return (ConfigurableEnvironment)environment;
}

//ApplicationContext准备 加载
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
//设置上下文的environment
context.setEnvironment(environment);
//应用上下文后处理
this.postProcessApplicationContext(context);
//在context refresh之前，对其应用ApplicationContextInitializer
this.applyInitializers(context);
//上下文准备（目前是空实现，有待扩展）
listeners.contextPrepared(context);
//打印启动日志和启动应用profile
if (this.logStartupInfo) {
this.logStartupInfo(context.getParent() == null);
this.logStartupProfileInfo(context);
}
//向beanFactory注册单例bean：命令行参数bean
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
if (printedBanner != null) {
//向beanFactory注册单例bean：banner bean
beanFactory.registerSingleton("springBootBanner", printedBanner);
}

    if (beanFactory instanceof DefaultListableBeanFactory) {
        ((DefaultListableBeanFactory)beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
    }

    Set