jar包：執行SpringBoot主類的main方法，啟動ioc容器，創建嵌入式的Servlet容器； war包：啟動服務器，**服務器啟動SpringBoot應用**【SpringBootServletInitializer】，啟動ioc容器； servlet3.0（Spring注解版）： 8.2.4 Shared libraries / runtimes pluggability： 規則： ? 1）、服務器啟動（web應用啟動）會創建當前web應用里面每一個jar包里面ServletContainerInitializer實例： ? 2）、ServletContainerInitializer的實現放在jar包的META-INF/services文件夾下，有一個名為javax.servlet.ServletContainerInitializer的文件，內容就是ServletContainerInitializer的實現類的全類名 ? 3）、還可以使用@HandlesTypes，在應用啟動的時候加載我們感興趣的類； 流程： 1）、啟動Tomcat 2）、org\springframework\spring-web\4.3.14.RELEASE\spring-web-4.3.14.RELEASE.jar!\META-INF\services\javax.servlet.ServletContainerInitializer： Spring的web模塊里面有這個文件：**org.springframework.web.SpringServletContainerInitializer** 3）、SpringServletContainerInitializer將@HandlesTypes(WebApplicationInitializer.class)標注的所有這個類型的類都傳入到onStartup方法的Set<Class<?>>；為這些WebApplicationInitializer類型的類創建實例； 4）、每一個WebApplicationInitializer都調用自己的onStartup；  5）、相當于我們的SpringBootServletInitializer的類會被創建對象，并執行onStartup方法 6）、SpringBootServletInitializer實例執行onStartup的時候會createRootApplicationContext；創建容器 ```java protected WebApplicationContext createRootApplicationContext( ServletContext servletContext) { //1、創建SpringApplicationBuilder SpringApplicationBuilder builder = createSpringApplicationBuilder(); StandardServletEnvironment environment = new StandardServletEnvironment(); environment.initPropertySources(servletContext, null); builder.environment(environment); builder.main(getClass()); ApplicationContext parent = getExistingRootWebApplicationContext(servletContext); if (parent != null) { this.logger.info("Root context already created (using as parent)."); servletContext.setAttribute( WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, null); builder.initializers(new ParentContextApplicationContextInitializer(parent)); } builder.initializers( new ServletContextApplicationContextInitializer(servletContext)); builder.contextClass(AnnotationConfigEmbeddedWebApplicationContext.class); //調用configure方法，子類重寫了這個方法，將SpringBoot的主程序類傳入了進來 builder = configure(builder); //使用builder創建一個Spring應用 SpringApplication application = builder.build(); if (application.getSources().isEmpty() && AnnotationUtils .findAnnotation(getClass(), Configuration.class) != null) { application.getSources().add(getClass()); } Assert.state(!application.getSources().isEmpty(), "No SpringApplication sources have been defined. Either override the " + "configure method or add an @Configuration annotation"); // Ensure error pages are registered if (this.registerErrorPageFilter) { application.getSources().add(ErrorPageFilterConfiguration.class); } //啟動Spring應用 return run(application); } ``` 7）、Spring的應用就啟動并且創建IOC容器 ```java public ConfigurableApplicationContext run(String... args) { StopWatch stopWatch = new StopWatch(); stopWatch.start(); ConfigurableApplicationContext context = null; FailureAnalyzers analyzers = null; configureHeadlessProperty(); SpringApplicationRunListeners listeners = getRunListeners(args); listeners.starting(); try { ApplicationArguments applicationArguments = new DefaultApplicationArguments( args); ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments); Banner printedBanner = printBanner(environment); context = createApplicationContext(); analyzers = new FailureAnalyzers(context); prepareContext(context, environment, listeners, applicationArguments, printedBanner); //刷新IOC容器 refreshContext(context); afterRefresh(context, applicationArguments); listeners.finished(context, null); stopWatch.stop(); if (this.logStartupInfo) { new StartupInfoLogger(this.mainApplicationClass) .logStarted(getApplicationLog(), stopWatch); } return context; } catch (Throwable ex) { handleRunFailure(context, listeners, analyzers, ex); throw new IllegalStateException(ex); } } ``` **==啟動Servlet容器，再啟動SpringBoot應用==**