SpringBoot整个启动过程的分析

@SpringBootApplication
public class CmsApplication {
 public static void main(String[] args) {
  SpringApplication.run(CmsApplication.class, args);
 }
}

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);//sources为具体的CmsApplication.class类
 }
...

public SpringApplication(Object... sources) {
  this.bannerMode = Mode.CONSOLE;
  this.logStartupInfo = true;
  this.addCommandLineProperties = true;
  this.headless = true;
  this.registerShutdownHook = true;
  this.additionalProfiles = new HashSet();
  this.initialize(sources);
 }
...

private void initialize(Object[] sources) {
  if (sources != null && sources.length > 0) {
   this.sources.addAll(Arrays.asList(sources));
  }
  this.webEnvironment = this.deduceWebEnvironment();
  this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
  this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));
  this.mainApplicationClass = this.deduceMainApplicationClass();
 }
...

public ConfigurableApplicationContext run(String... args) {
  StopWatch stopWatch = new StopWatch();// 构造一个任务执行观察器
  stopWatch.start();// 开始执行，记录开始时间
  ConfigurableApplicationContext context = null;
  FailureAnalyzers analyzers = null;
  this.configureHeadlessProperty();
  // 获取SpringApplicationRunListeners，内部只有一个EventPublishingRunListener
  SpringApplicationRunListeners listeners = this.getRunListeners(args);
  // 封装成SpringApplicationEvent事件然后广播出去给SpringApplication中的listeners所监听，启动监听
  listeners.starting();
  try {
   // 构造一个应用程序参数持有类
   ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
   // 加载配置环境
   ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
   Banner printedBanner = this.printBanner(environment);
   // 创建Spring容器（使用BeanUtils.instantiate）
   context = this.createApplicationContext();
   // 若容器创建失败，分析输出失败原因
   new FailureAnalyzers(context);
   // 设置容器配置环境，监听等
   this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
   // 刷新容器
   this.refreshContext(context);
   this.afterRefresh(context, applicationArguments);
   // 广播出ApplicationReadyEvent事件给相应的监听器执行
   listeners.finished(context, (Throwable)null);
   stopWatch.stop();// 执行结束，记录执行时间
   if (this.logStartupInfo) {
    (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
   }
   return context;// 返回Spring容器
  } catch (Throwable var9) {
   this.handleRunFailure(context, listeners, (FailureAnalyzers)analyzers, var9);
   throw new IllegalStateException(var9);
  }
 }

protected ConfigurableApplicationContext createApplicationContext() {
  Class<?> contextClass = this.applicationContextClass;
  if (contextClass == null) {
   try {
    contextClass = Class.forName(this.webEnvironment ? "org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext" : "org.springframework.context.annotation.AnnotationConfigApplicationContext");
   } catch (ClassNotFoundException var3) {
    throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", var3);
   }
  }
  return (ConfigurableApplicationContext)BeanUtils.instantiate(contextClass);
 }

public void refresh() throws BeansException, IllegalStateException {
  Object var1 = this.startupShutdownMonitor;
  synchronized(this.startupShutdownMonitor) {
   this.prepareRefresh();
   ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
   this.prepareBeanFactory(beanFactory);
   try {
    this.postProcessBeanFactory(beanFactory);
    this.invokeBeanFactoryPostProcessors(beanFactory);
    this.registerBeanPostProcessors(beanFactory);
    this.initMessageSource();
    this.initApplicationEventMulticaster();
    this.onRefresh();
    this.registerListeners();
    this.finishBeanFactoryInitialization(beanFactory);
    this.finishRefresh();
   } catch (BeansException var9) {
    if (this.logger.isWarnEnabled()) {
     this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9);
    }
    this.destroyBeans();
    this.cancelRefresh(var9);
    throw var9;
   } finally {
    this.resetCommonCaches();
   }
  }
 }