SpringBoot启动流程、原理

SpringBoot启动流程

1、创建SpringApplication对象

initialize(sources);
private void initialize(Object[] sources) {//保存主配置类if (sources !&＃61; null && sources.length > 0) {this.sources.addAll(Arrays.asList(sources));}//判断当前是否一个web应用this.webEnvironment &＃61; deduceWebEnvironment();//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer&＃xff1b;然后保存起来setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));//从类路径下找到ETA-INF/spring.factories配置的所有ApplicationListenersetListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));//从多个配置类中找到有main方法的主配置类this.mainApplicationClass &＃61; deduceMainApplicationClass();
}


运行run方法

public ConfigurableApplicationContext run(String... args) {StopWatch stopWatch &＃61; new StopWatch();stopWatch.start();ConfigurableApplicationContext context &＃61; null;FailureAnalyzers analyzers &＃61; null;configureHeadlessProperty();//获取SpringApplicationRunListeners&＃xff1b;从类路径下META-INF/spring.factoriesSpringApplicationRunListeners listeners &＃61; getRunListeners(args);//回调所有的获取SpringApplicationRunListener.starting()方法listeners.starting();try {//封装命令行参数ApplicationArguments applicationArguments &＃61; new DefaultApplicationArguments(args);//准备环境ConfigurableEnvironment environment &＃61; prepareEnvironment(listeners,applicationArguments);//创建环境完成后回调SpringApplicationRunListener.environmentPrepared()&＃xff1b;表示环境准备完成Banner printedBanner &＃61; printBanner(environment);//创建ApplicationContext&＃xff1b;决定创建web的ioc还是普通的ioccontext &＃61; createApplicationContext();analyzers &＃61; new FailureAnalyzers(context);//准备上下文环境;将environment保存到ioc中&＃xff1b;而且applyInitializers()&＃xff1b;//applyInitializers()&＃xff1a;回调之前保存的所有的ApplicationContextInitializer的initialize方法//回调所有的SpringApplicationRunListener的contextPrepared()&＃xff1b;//prepareContext(context, environment, listeners, applicationArguments,printedBanner);//prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded&＃xff08;&＃xff09;&＃xff1b;//s刷新容器&＃xff1b;ioc容器初始化&＃xff08;如果是web应用还会创建嵌入式的Tomcat&＃xff09;&＃xff1b;Spring注解版//扫描&＃xff0c;创建&＃xff0c;加载所有组件的地方&＃xff1b;&＃xff08;配置类&＃xff0c;组件&＃xff0c;自动配置&＃xff09;refreshContext(context);//从ioc容器中获取所有的ApplicationRunner和CommandLineRunner进行回调//ApplicationRunner先回调&＃xff0c;CommandLineRunner再回调afterRefresh(context, applicationArguments);//所有的SpringApplicationRunListener回调finished方法listeners.finished(context, null);stopWatch.stop();if (this.logStartupInfo) {new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);}//整个SpringBoot应用启动完成以后返回启动的ioc容器&＃xff1b;return context;}catch (Throwable ex) {handleRunFailure(context, listeners, analyzers, ex);throw new IllegalStateException(ex);}
}