public static ConfigurableApplicationContext run(Object source, String... args) {return run(new Object[] { source }, args);
}public static ConfigurableApplicationContext run(Object[] sources, String[] args) {return new SpringApplication(sources).run(args);
}

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {this.resourceLoader = resourceLoader;Assert.notNull(primarySources, "PrimarySources must not be null");this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));this.webApplicationType = WebApplicationType.deduceFromClasspath();//用来查找每个jar和类路径下的/META-INF/spring.factories文件，并获取其中的特定接口的配置的setInitializers((Collection) getSpringFactoriesInstances( ApplicationContextInitializer.class)); //找出每个jar和类路径下的/META-INF/spring.factories文件中配置的ApplicationContextInitializer类setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));this.mainApplicationClass = deduceMainApplicationClass(); //推断出带有main方法的运行类
}

public ConfigurableApplicationContext run(String... args) {//StopWatch作用是用来统计spring实例运行时间StopWatch stopWatch = new StopWatch();stopWatch.start();//ConfigurableApplicationContext接口提供了对Spring容器的配置功能ConfigurableApplicationContext context = null;Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();configureHeadlessProperty();SpringApplicationRunListeners listeners = getRunListeners(args);listeners.starting();try {ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);configureIgnoreBeanInfo(environment);Banner printedBanner = printBanner(environment);context = createApplicationContext();exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,new Class[] { ConfigurableApplicationContext.class }, context);// 1. 会执行ApplicationContextInitializer接口进行初始化工作// 2. 对外发布监听事件// 3. 优先创建有特定作用的单例bean// 4. 把带有main方法的主类作为bean的配置源，并从配置源中加载bean信息到容器中
            prepareContext(context, environment, listeners, applicationArguments,printedBanner);//spring容器的生命周期处理，该方法完成后单例bean实例就创建了
            refreshContext(context);afterRefresh(context, applicationArguments);stopWatch.stop();if (this.logStartupInfo) {new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);}//对外发布监听事件
            listeners.started(context);//我们在开发中可能会有这样的情景。需要在容器启动的时候执行一些内容。比如读取配置文件，数据库连接之类的。SpringBoot给我们提供了两个接口来帮助我们实现这种需求。这两个接口分别为CommandLineRunner和ApplicationRunner。他们的执行时机为容器启动完成的时候。
            callRunners(context, applicationArguments);}catch (Throwable ex) {handleRunFailure(context, ex, exceptionReporters, listeners);throw new IllegalStateException(ex);}try {//发布监听事件
            listeners.running(context);}catch (Throwable ex) {handleRunFailure(context, ex, exceptionReporters, null);throw new IllegalStateException(ex);}return context;}