SpringBoot启动原理

//调用SpringApplication类的静态方法
ConfigurableApplicationContext run(Class primarySource, String... args)
ConfigurableApplicationContext run(Class[] primarySources, String[] args){
    //构造SpringApplication类对象，
    //调用的SpringApplication的双参构造方法 SpringApplication(ResourceLoader resourceLoader,         
    // Class... primarySources)
    return (new SpringApplication(primarySources)).run(args);
}

public SpringApplication(ResourceLoader resourceLoader, Class... primarySources) {
        //初始化值sources，bannerMode，logStartupInfo，registerShutdownHook，resourceLoader
        //additionalProfiles  = new HashSet()，sources= new LinkedHashSet()
        
       //primarysources 不能为空，为空即启动报错
        this.primarySources = new LinkedHashSet(Arrays.asList(primarySources));
        
        //使用枚举 public enum WebApplicationType {NONE，SERVLET，REACTIVE}
        //如果有reactive.DispatcherHandler类则为WebApplicationType.REACTIVE
        //如果有javax.servlet.Servlet和context.ConfigurableWebApplicationContext类则为
        //WebApplicationType.SERVLET
        this.webApplicationType = this.deduceWebApplicationType();


        //1.在spring-boot:版本号.jar和spring-boot-autoconfigure:版本号.jar下
        //  METAINF下spring.factories下
        //  ApplicationContextInitializer组下的6个类，进行实例化,且对实现Order的接口进行排序 
        //2.SpringFactoriesLoader的静态方法loadFactoryNames方法及该方法内            
        //  loadSpringFactories()读取spring.factores的所有内容到cache。然后 
        //  ApplicationContextInitializer组的获取的6个类，
        //3.排序后  1.DelegatingApplicationContextInitializer  
        //       2.ContextIdApplicationContextInitializer  ...等等6个                                      
         this.setInitializers(this.getSpringFactoriesInstances(
ApplicationContextInitializer.class));
        
        //用上述同样的方法，获取METAINF下spring.factories下ApplicationContextInitializer组     
        //下的监听器，进行实例化，且对实现Order的接口进行排序 
        //第一个监听器类ConfigFileApplicationListener
        this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));
        
        //得到启动main方法的类的class。
        //通过new RuntimeException()对象，得到StackTraceElement[]对象中是main方法的 
        // StackTraceElement对象，通过StackTraceElement对象.getClassName()得到Class
        this.mainApplicationClass = this.deduceMainApplicationClass();
}


public ConfigurableApplicationContext run(String... args) {

        //StopWatch自带计时工具类。StopWatch.TaskInfo为内部类任务类其属性：     
        //taskName，任务名称。timeMillis 该任务耗时
        //空参构造id=""
        StopWatch stopWatch = new StopWatch();
        //任务名称taskName=""。
        //id="",taskName=""的耗时开始计时
        stopWatch.start();
        
        ConfigurableApplicationContext context = null;
        Collection exceptionReporters = new ArrayList();
        
        //向系统System对象配置HeadLess属性
        this.configureHeadlessProperty();
        
        //SpringFactoriesLoader的cache中得到SpringApplicationRunListener组下的监听器
        // 只有一个EventPublishingRunListener由两个重要属性
        //        SpringApplication application=springApplication对象
        // SimpleApplicationEventMulticaster initialMulticaster对象
        SpringApplicationRunListeners listeners = this.getRunListeners(args);
        
        //通过调用initialMulticaster对象调用监听器的onApplicationEvent()
        //下面是四个ApplicationStartEvent事件对象对应的监听器
        //LoggingApplicationListener 初始化loggingSystem=LogbackLoggingSystem,
        //  并且loggingSystem.beforeInitialize()->TurboFilterList表中添加FilterReply.DENY
        //BackgroundPreinitializer  开启另为线程后台完成
        //   ConversionServiceInitializer()，ValidationInitializer()
        //   MessageConverterInitializer(),CharsetInitializer()等   
        //DelegatingApplicationListener  doNothing
        //LiquibaseServiceLocatorApplicationListener doNothing
        listeners.starting();

        Collection exceptionReporters;
        try { 
            //封装args
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            
            //1.根据webApplicationType=WebApplicationType.SERVLET创建 
            //StandardServletEnvironment对象，否则创建StandardEnvironment对象
            //StandardServletEnvironment对象属性propertySource有
            //   servletConfigInitParams，servletContextInitParams，
            //   systemProperties，systemEnvironment，commandLineArgs,applicationConfig: 
            //   [classpath:/application.properties]
            //2.EventPublishingRunListener对象environmentPrepared(environment)方法
            //  内部调用 
            //initialMulticaster.multicastEvent(ApplicationEnvironmentPreparedEvent)
            // 对应ConfigFileApplicationListener,AnsiOutputApplicationListener
            // LoggingApplicationListener,ClasspathLoggingApplicationListener
            //BackgroundPreinitializer 等等
            ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
            
            //向System对象设置spring.beaninfo.ignore=true
            this.configureIgnoreBeanInfo(environment);

            //如果bannerMode ！= Mode.OFF，则使用默认Banner为SpringBootBanner
            Banner printedBanner = this.printBanner(environment);
            
            //如果webApplicationType=SERVLET，则
            // 利用Class.forName(web.servlet.context.AnnotationConfigServletWebServer     
            //       ApplicationContext）空参构造创建对象，同时初始化this.refreshed=false
            //       和this.beanFactory = new DefaultListableBeanFactory()和this.
            //       ignoreDependencyInterface=BeanNameAware/BeanFactoryAware/
            //       BeanClassLoaderAware.class等等                        
            // 1.初始化this.reader = new AnnotatedBeanDefinitionReader(this);
            //      初始化this.beanNameGenerator = new AnnotationBeanNameGenerator()
            //      初始化this.scopeMetadataResolver = new 
            //                                     AnnotationScopeMetadataResolver()
            //      初始化this.registry = registry(BeanDefinitionRegistry);
            //      初始化this.conditionEvaluator = new ConditionEvaluator(registry, 
            //                                      environment, (ResourceLoader)null)
            //      AnnotationConfigUtils.registerAnnotationConfig
            //                                      Processors(this.registry) 
            //                设置DefaultListableBeanFactory beanFactory
            //                   beanFactory.setDependencyComparator()
            //                   beanFactory.setAutowireCandidateResolver
            //                   beanFactory的beanDefinitionNames
            //                   beanDefinitionMap,value为RootBeanDefinition分别为
            //                       annotation.internalConfigurationAnnotationProcessor
            //                       annotation.internalAutowiredAnnotationProcessor
            //                       annotation.internalRequiredAnnotationProcessor
            //                       annotation.internalCommonAnnotationPrecessor             
            //                       event.internalEventListenerProcessor
            //                       event.internalEventListenerFactory
            // 2.初始化this.scanner = new ClassPathBeanDefinitionScanner(this);
            //      this.beanDefinitionDefaults = new BeanDefinitionDefaults()
            //      this.beanNameGenerator = new AnnotationBeanNameGenerator()
            //      this.scopeMetadataResolver = new AnnotationScopeMetadataResolver()
            //      this.includeAnnotationConfig = true
            //      this.registry = registry;
            //      this.includeFilters=Component,javax.ManagedBean
            //      this.excludeFilters为0
            //      this.setEnvironment
            //      this.setResourceLoader
            context = this.createApplicationContext();
            //从缓存中加载SpringBootExceptionReporter组的类 ，封装成FailureAnalyzers
            //类，其属性List analyzers。   
            exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
            
            // 设置AnnotationConfigServletWebServerApplicationContext对象context     
            //   context.setEnvironment(environment) 
            //   SpringApplication对象.postProcessApplicationContext(context)
            //          beanNameGenerator与resourceLoader的设置
            //   SpringApplication对象.applyInitializers(context) 
            //          调用ApplicationContextInitializer接口的实现类的initialize()方法
            //          例如ContextIdApplicationContextInitializer.initialize()方法
            //            为applicationContext设置id=application和注册内部类ContextId
            //          例如ServerPortInfoApplicationContextInitializer.initialize()
            //            为applicationContext设置监听器ServerPortIn...ContextInitializer
            //          例如SharedMetadataReaderFactoryContextInitializer.initialize
            //            为applicationContext.addBeanFactoryPostProcessor
            //            CachingMetadataReaderFactoryPostProcessor对象   
            //   listeners.contextPrepared(context)
            //         使用EventPublishingRunListener.contextPrepared(context) nothing 
            //   打印启动相关日志和配置文件相关日志
            //   向DefaultListableBeanFactory中sinletonObjects注册bean
            //          springApplicationArguments和springBootBanner
            //   Set