SpringBoot启动流程

this.resourceLoader = resourceLoader设置资源加载器resourceLoader，本例中为null

this.mainApplicationClass = deduceMainApplicationClass();推断应用引导类

1. 构造SpringApplication实例SpringApplication application = new SpringApplication(MyApplication.class)

setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));加载Spring应用上下文初始化器

ConfigurableApplicationContext context = createApplicationContext();创建Spring应用上下文

DefaultBootstrapContext bootstrapContext = createBootstrapContext();使用bootstrapRegistryInitializers初始化器来初始化启动上下文

refreshContext(context);Spring应用上下文启动阶段

ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);装配applicationArguments，简化Spring应用命令行启动参数

setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));加载Spring应用事件监听器

this.webApplicationType = WebApplicationType.deduceFromClasspath();从类路径推断web应用类型，本例中为Servlet

2. 配置Spring应用（可选）

  this.bootstrapRegistryInitializers = getBootstrapRegistryInitializersFromSpringFactories();加载Spring应用启动注册初始化器bootstrapRegistryInitializers，在运行阶段用

this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));设置主配置类集合primarySources本例中为com.example.springstudy.MyApplication

3. 运行阶段application.run()