聊聊springboot的启动事件

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本文主要研究一下springboot的启动事件

SpringApplicationEvent

org/springframework/boot/context/event/SpringApplicationEvent.java

public abstract class SpringApplicationEvent extends ApplicationEvent {

	private final String[] args;

	public SpringApplicationEvent(SpringApplication application, String[] args) {
		super(application);
		this.args = args;
	}

	public SpringApplication getSpringApplication() {
		return (SpringApplication) getSource();
	}

	public final String[] getArgs() {
		return this.args;
	}

}

SpringApplicationEvent继承了ApplicationEvent，它有几个子类分表是ApplicationStartingEvent、ApplicationEnvironmentPreparedEvent、ApplicationContextInitializedEvent、ApplicationPreparedEvent、ApplicationStartedEvent、ApplicationReadyEvent，期间有异常则抛出ApplicationFailedEvent

SpringApplication.run

org/springframework/boot/SpringApplication.java

	public ConfigurableApplicationContext run(String... args) {
		StopWatch stopWatch = new StopWatch();
		stopWatch.start();
		ConfigurableApplicationContext context = null;
		Collection 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;
	}

SpringApplication的run方法，先触发listeners.starting()，然后执行了prepareEnvironment，之后createApplicationContext，再进行prepareContext和refreshContext，最后触发listeners.started(context)，之后执行callRunners，最后触发listeners.running(context)，如有异常则会执行handleRunFailure

prepareEnvironment

	private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
			ApplicationArguments applicationArguments) {
		// Create and configure the environment
		ConfigurableEnvironment environment = getOrCreateEnvironment();
		configureEnvironment(environment, applicationArguments.getSourceArgs());
		ConfigurationPropertySources.attach(environment);
		listeners.environmentPrepared(environment);
		bindToSpringApplication(environment);
		if (!this.isCustomEnvironment) {
			environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
					deduceEnvironmentClass());
		}
		ConfigurationPropertySources.attach(environment);
		return environment;
	}

prepareEnvironment会触发listeners.environmentPrepared(environment)，即发布ApplicationEnvironmentPreparedEvent

prepareContext

	private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
			SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
		context.setEnvironment(environment);
		postProcessApplicationContext(context);
		applyInitializers(context);
		listeners.contextPrepared(context);
		if (this.logStartupInfo) {
			logStartupInfo(context.getParent() == null);
			logStartupProfileInfo(context);
		}
		// Add boot specific singleton beans
		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
		beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
		if (printedBanner != null) {
			beanFactory.registerSingleton("springBootBanner", printedBanner);
		}
		if (beanFactory instanceof DefaultListableBeanFactory) {
			((DefaultListableBeanFactory) beanFactory)
					.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
		}
		if (this.lazyInitialization) {
			context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
		}
		// Load the sources
		Set