public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {return (new SpringApplication(primarySources)).run(args);}

run方法

	public ConfigurableApplicationContext run(String... args) {//创建一个StopWatch对象，开始记录run()启动过程时长；StopWatch stopWatch = new StopWatch();stopWatch.start();ConfigurableApplicationContext context = null;Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();configureHeadlessProperty();//1.创建应用监听器并启动//从META-INF/spring.factories文件中获取监听器 -SpringApplicationRunListener//径下的 META-INF/spring.factories文件中找 对应SpringApplicationRunListener的全路径数组，并通过createSpringFactoriesInstances()方法实例化成对象返回；SpringApplicationRunListeners listeners = getRunListeners(args);//启动监听器 回调之前获得的所有SpringApplicationRunListener对象的starting()方法,启动监听listeners.starting();try {// 获取命令行参数如 --server.port 等ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);//2. 创建运行环境environment，创建当前SpringBoot应用要使用的environmentConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);configureIgnoreBeanInfo(environment);//打印Banner，也可以自定义启动logo，比如在resources路径下创建一个banner.txt文件，将你想打印的图标放入其中Banner printedBanner = printBanner(environment);//3 创建ApplicationContext容器，根据类型决定是创建普通WEB容器还是REACTIVE容器还是普通Annotation的ioc 容器context = createApplicationContext();//获取异常报告器SpringBootExceptionReporter//exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,new Class[] { ConfigurableApplicationContext.class }, context);//从initializers集合中遍历所有的ApplicationContextInitializer，并通过initializer.initialize( )方法初始化//4.Spring容器前置处理prepareContext(context, environment, listeners, applicationArguments, printedBanner);//5. 刷新容器refreshContext(context);//6.spring容器后置处理afterRefresh(context, applicationArguments);//计时结束stopWatch.stop();if (this.logStartupInfo) {new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);}//7.发布结束执行通知listeners.started(context);//8.执行RunnerscallRunners(context, applicationArguments);}catch (Throwable ex) {//如果有异常就抛出handleRunFailure(context, ex, exceptionReporters, listeners);throw new IllegalStateException(ex);}try {//9.发布应用上下文就绪事件listeners.running(context);}catch (Throwable ex) {handleRunFailure(context, ex, exceptionReporters, null);throw new IllegalStateException(ex);}return context;}

1-getRunListeners

private SpringApplicationRunListeners getRunListeners(String[] args) {Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };return new SpringApplicationRunListeners(logger,getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));}

• getSpringFactoriesInstances 最终调用
  org.springframework.core.io.support.SpringFactoriesLoader#loadSpringFactories

public static final String FACTORIES_RESOURCE_LOCATION = “META-INF/spring.factories”;

private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {MultiValueMap<String, String> result = cache.get(classLoader);if (result != null) {return result;}try {//META-INF/spring.factories从文件中获取指定类型的并最后实例化Enumeration<URL> urls = (classLoader != null ?classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));result = new LinkedMultiValueMap<>();while (urls.hasMoreElements()) {URL url = urls.nextElement();UrlResource resource = new UrlResource(url);Properties properties = PropertiesLoaderUtils.loadProperties(resource);for (Map.Entry<?, ?> entry : properties.entrySet()) {String factoryTypeName = ((String) entry.getKey()).trim();for (String factoryImplementationName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) {result.add(factoryTypeName, factoryImplementationName.trim());}}}cache.put(classLoader, result);return result;}catch (IOException ex) {throw new IllegalArgumentException("Unable to load factories from location [" +FACTORIES_RESOURCE_LOCATION + "]", ex);}}

2. prepareEnvironment

准备环境

	private ConfigurableEnvironment getOrCreateEnvironment() {if (this.environment != null) {return this.environment;}switch (this.webApplicationType) {case SERVLET:return new StandardServletEnvironment();case REACTIVE:return new StandardReactiveWebEnvironment();default:return new StandardEnvironment();}}private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,ApplicationArguments applicationArguments) {// Create and configure the environment//创建一个environment对象ConfigurableEnvironment environment = getOrCreateEnvironment();//配置环境 PropertySources ProfilesconfigureEnvironment(environment, applicationArguments.getSourceArgs());//PropertySourcesConfigurationPropertySources.attach(environment);//环境准备listeners.environmentPrepared(environment);//将环境绑定到oSpringApplication(bindToSpringApplication(environment);if (!this.isCustomEnvironment) {environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,deduceEnvironmentClass());}//配置PropertySources-如果有attach到environmentConfigurationPropertySources.attach(environment);return environment;}

3.createApplicationContext();

	protected ConfigurableApplicationContext createApplicationContext() {//获取上下文的类Class<?> contextClass = this.applicationContextClass;if (contextClass == null) {try {switch (this.webApplicationType) {//判断Web应用类型case SERVLET:contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);break;case REACTIVE:contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);break;default:contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);}}catch (ClassNotFoundException ex) {throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", ex);}}return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);}

4.prepareContext

private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {//上下文设置环境context.setEnvironment(environment);//处理上下文，Bean的生成器和资源加载器postProcessApplicationContext(context);//从initializers集合中遍历所有的ApplicationContextInitializer，并通过initializer.initialize( )方法初始化applyInitializers(context);//回调SpringApplicationRunListener对象的contextPrepared()方法，表示容器已准备listeners.contextPrepared(context);//启动日志if (this.logStartupInfo) {logStartupInfo(context.getParent() == null);logStartupProfileInfo(context);}//注册启动参数的Bean，将容器指定的参数封装为Bean，注入容器中// Add boot specific singleton beansConfigurableListableBeanFactory beanFactory = context.getBeanFactory();beanFactory.registerSingleton("springApplicationArguments", applicationArguments);if (printedBanner != null) {beanFactory.registerSingleton("springBootBanner", printedBanner);}if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory) beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);}//是否为延迟加载 是就添加LazyInitializationBeanFactoryPostProcessorif (this.lazyInitialization) {context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());}//加载所有资源// Load the sourcesSet<Object> sources = getAllSources();Assert.notEmpty(sources, "Sources must not be empty");/*** 加载我们应用的启动类，并注入到容器中*/load(context, sources.toArray(new Object[0]));//触发所有SpringApplicationRunListeners的contextLoaded事件方法listeners.contextLoaded(context);}

5.refreshContext就是去

org.springframework.context.support.AbstractApplicationContext#refresh

private void refreshContext(ConfigurableApplicationContext context) {
//去Spring IOC容器完成Bean的生命周期refresh(context);if (this.registerShutdownHook) {try {context.registerShutdownHook();}catch (AccessControlException ex) {// Not allowed in some environments.}}}

6.afterRefresh 空方法

protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) {}

可以自已写一些扩展

7.listeners.started(context);

	void started(ConfigurableApplicationContext context) {//获取SpringApplicationRunListener 所有监听器，循环启动for (SpringApplicationRunListener listener : this.listeners) {listener.started(context);}}

8.callRunners

	private void callRunners(ApplicationContext context, ApplicationArguments args) {List<Object> runners = new ArrayList<>();//获取所有ApplicationRunner接口的实现类 默认没有实现runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());//获取所有CommandLineRunner --默认没有实现runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());//排序AnnotationAwareOrderComparator.sort(runners);for (Object runner : new LinkedHashSet<>(runners)) {if (runner instanceof ApplicationRunner) {callRunner((ApplicationRunner) runner, args);}if (runner instanceof CommandLineRunner) {callRunner((CommandLineRunner) runner, args);}}}private void callRunner(ApplicationRunner runner, ApplicationArguments args) {try {//运行(runner).run(args);}catch (Exception ex) {throw new IllegalStateException("Failed to execute ApplicationRunner", ex);}}

9.发布应用上下文就绪事件 listeners.running(context);

listeners.running(context);void running(ConfigurableApplicationContext context) {for (SpringApplicationRunListener listener : this.listeners) {//获取SpringApplicationRunListener 类型的所有监听器 发布事件ApplicationReadyEventlistener.running(context); }}@Overridepublic void running(ConfigurableApplicationContext context) {context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context));}

SpringApplication监听器

SpringApplication对象创建和run()方法的运行过程中，我们可以发现有几个重要的事件回调机制，分别是：

ApplicationContextInitializer
SpringApplicationRunListener
ApplicationRunner
CommandLineRunner
这几个重要的事件回调机制在很多环境下都有应用，例如：

启动前的环境检测
启动时的配置初始化
启动后的数据初始化