SpringBoot事件机制

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();// ApplicationStartingEvent

    try {
       ApplicationArguments applicationArguments = new DefaultApplicationArguments(
             args);

       ConfigurableEnvironment environment = prepareEnvironment(listeners,
             applicationArguments);// ApplicationEnvironmentPreparedEvent

       configureIgnoreBeanInfo(environment);
       Banner printedBanner = printBanner(environment);
       context = createApplicationContext();
       exceptionReporters = getSpringFactoriesInstances(
             SpringBootExceptionReporter.class,
             new Class[] { ConfigurableApplicationContext.class }, context);

       prepareContext(context, environment, listeners, applicationArguments,
             printedBanner);// ApplicationContextInitializedEvent, ApplicationPreparedEvent

       refreshContext(context);
       afterRefresh(context, applicationArguments);
       stopWatch.stop();
       if (this.logStartupInfo) {
          new StartupInfoLogger(this.mainApplicationClass)
                .logStarted(getApplicationLog(), stopWatch);
       }
       listeners.started(context);// ApplicationStartedEvent
       callRunners(context, applicationArguments);
    }
    catch (Throwable ex) {
       handleRunFailure(context, ex, exceptionReporters, listeners); // ApplicationFailedEvent
       throw new IllegalStateException(ex);
    }

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

public class StartApplication {
    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(StartApplication.class);
        app.addListeners(new CustomListener());
        app.run(args);
    }

    public static class CustomListener implements ApplicationListener<ApplicationEvent> {
        @Override
        public void onApplicationEvent(ApplicationEvent event) {
            if (event instanceof ApplicationStartingEvent) {

            }
            else if (event instanceof ApplicationEnvironmentPreparedEvent) {

            }
            else if (event instanceof ApplicationPreparedEvent) {

            }
            else if (event instanceof ContextClosedEvent && ((ContextClosedEvent) event)
                    .getApplicationContext().getParent() == null) {
            }
            else if (event instanceof ApplicationFailedEvent) {

            }
        }
    }
}