springboot啟動流程簡述

 

springboot啟動流程簡述

程序入口

@SpringBootApplication
public class App {
    public static void main(String[] args) {
    SpringApplication application = new SpringApplication(AppServer.class);
    application.run(args);
    }
}

SpringApplication 構造函數：
初始化上下文的各種接口，實例化監聽器

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
   this.resourceLoader = resourceLoader;
   Assert.notNull(primarySources, "PrimarySources must not be null");
   this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
   this.webApplicationType = WebApplicationType.deduceFromClasspath();
   setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
   setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
   this.mainApplicationClass = deduceMainApplicationClass();
}

run方法
1、開啟一個秒表統計啟動時間並打印日志
2、初始化監聽器，啟動監聽
3、新建和獲取當前的Environment實例：
封裝main方法的參數，初始化參數，寫入到 Environment中，發布 ApplicationEnvironmentPreparedEvent（環境事件），做一些綁定后返回Environment。
4、創建上下文實例：
加載創建的上下文實例，加載中，先填充Environment環境和設置的參數，如果application有設置beanNameGenerator（bean）、resourceLoader（加載器）就將其注入到上下文中
調用初始化的切面，發布ApplicationContextInitializedEvent（上下文初始化）事件；
5、刷新上下文。在刷新上下文里面，做一些，切面方法的調用，注冊切面bean，listener注冊（ 到廣播器中），清理緩存等。
6、發布啟動完成的事件，並調用監聽者的方法。
（方法調用的細節這里沒有點擊進去一步步描述，只是自己的一點理解，有錯誤歡迎指正，謝謝）

public ConfigurableApplicationContext run(String... args) {
   StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
   configureHeadlessProperty();
   SpringApplicationRunListeners listeners = getRunListeners(args);
   listeners.starting();
   try {
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
      ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
      configureIgnoreBeanInfo(environment);
      Banner printedBanner = printBanner(environment);
      context = createApplicationContext();
      exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
            new Class[] { ConfigurableApplicationContext.class }, context);
      prepareContext(context, environment, listeners, applicationArguments, printedBanner);
      refreshContext(context);
      afterRefresh(context, applicationArguments);
      stopWatch.stop();
      if (this.logStartupInfo) {
         new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
      }
      listeners.started(context);
      callRunners(context, applicationArguments);
   }
   catch (Throwable ex) {
      handleRunFailure(context, ex, exceptionReporters, listeners);
      throw new IllegalStateException(ex);
   }


   try {
      listeners.running(context);
   }
   catch (Throwable ex) {
      handleRunFailure(context, ex, exceptionReporters, null);
      throw new IllegalStateException(ex);
   }
   return context;
}