一、Application启动类中main方法启动
@SpringBootApplication(scanBasePackages = {"com.springboot.lean"})
public class Application {public static void main(String[] args) {SpringApplication.run(Application.class, args);}
}1.1 @SpringBootApplication注解
1.2 SpringApplication.run方法
主要做两件事，首先根据默认设置和用户提供的参数创建一个新的SpringApplication实例
private void initialize(Object[] sources) {if (sources != null && sources.length > 0) {this.sources.addAll(Arrays.asList(sources));}this.webEnvironment = deduceWebEnvironment();setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));this.mainApplicationClass = deduceMainApplicationClass();
}然后调用真正的run方法，启动Spring application，并创建及刷新ApplicationContext
public ConfigurableApplicationContext run(String... args) {//计数器，用于计算并打印容器启动时长StopWatch stopWatch = new StopWatch();stopWatch.start();ConfigurableApplicationContext context = null;FailureAnalyzers analyzers = null;//设置java.awt.headless属性，java.awt.headless是J2SE的一种模式，//用于在缺失显示屏、鼠标或者键盘时的系统配置。对于后端服务来讲，很多都是需要将这个属性设置为true的configureHeadlessProperty();//调用getSpringFactoriesInstances从META-INF/spring.factories方法中获取并创建所有的SpringApplicationRunListener，//底层实际会调用SpringFactoriesLoader.loadFactoryNames(type, classLoader)SpringApplicationRunListeners listeners = getRunListeners(args);//启动监听器，例如EventPublishingRunListenerlisteners.starting();try {//根据用户自定义参数构建应用参数ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);//首先创建或配置一个ConfigurableEnvironment实例，然后将应用参数设置进环境对象中ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);//打印启动图形，图形文件默认在META-INF下的banner.txt文件中，关键类为SpringApplicationBannerPrinterBanner printedBanner = printBanner(environment);//创建application上下文，根据webEnvironment判断是加载AnnotationConfigApplicationContext类实例还是//AnnotationConfigEmbeddedWebApplicationContext类实例，这两个对象都会注册所有相关的注解后处理器//例如@Configuration，@Autowiredcontext = createApplicationContext();//创建失败分析器实例analyzers = new FailureAnalyzers(context);prepareContext(context, environment, listeners, applicationArguments, printedBanner);//调用AbstractApplicationContext.refresh方法，进入spring启动流程refreshContext(context);//在容器启动刷新后做些事情，模板方法，用于自定义扩展实现afterRefresh(context, applicationArguments);//监听器发布容器启动完成事件listeners.finished(context, null);stopWatch.stop();if (this.logStartupInfo) {//打印容器启动时长new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);}return context;}catch (Throwable ex) {//解析容器加载失败信息，并打印堆栈错误日志handleRunFailure(context, listeners, analyzers, ex);throw new IllegalStateException(ex);}
}
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