发布日期: 2024-04-10

SpringBoot Event

Spring Framework 框架中的事件和监听器无处不在，比如在启动过程中会发送一系列的事件，发送的事件顺序如下：

ApplicationStartingEvent

在Spring Boot应用运行开始时，且进行任何处理之前发送（除了监听器和初始化器注册）

public ConfigurableApplicationContext run(String... args) {
        long startTime = System.nanoTime();
        DefaultBootstrapContext bootstrapContext = createBootstrapContext();
        ConfigurableApplicationContext context = null;
        configureHeadlessProperty();
    // 获取定义的Listener
        SpringApplicationRunListeners listeners = getRunListeners(args);
    // Application Starting Event 提醒位置
        listeners.starting(bootstrapContext, this.mainApplicationClass);
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            context.setApplicationStartup(this.applicationStartup);
            prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
            }
            listeners.started(context, timeTakenToStartup);
            callRunners(context, applicationArguments);
      
      
      ....
        
        
        }
}

ApplicationEnvironmentPrepareEvent

这个事件在当已知要在上下文中使用Spring环境environment时，在spring上下文context创建之前发送。

public ConfigurableApplicationContext run(String... args) {
        long startTime = System.nanoTime();
        DefaultBootstrapContext bootstrapContext = createBootstrapContext();
        ConfigurableApplicationContext context = null;
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
    //  1.ApplicationStartingEvent 提醒位置
        listeners.starting(bootstrapContext, this.mainApplicationClass);
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            // 2.ApplicationEnvironmentPrepareEvent 提醒位置
      ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            context.setApplicationStartup(this.applicationStartup);
      // 3.ApplicationContextInitializedEvent 提醒位置
            prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
      // 
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
            }
            listeners.started(context, timeTakenToStartup);
            callRunners(context, applicationArguments);
      
      
      ....
        
        
        }
}

ApplicationContextInitializedEvent
ApplicationPreparedEvent

private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context,
            ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
            ApplicationArguments applicationArguments, Banner printedBanner) {
        context.setEnvironment(environment);
        postProcessApplicationContext(context);
        addAotGeneratedInitializerIfNecessary(this.initializers);
        applyInitializers(context);
    // 3. ApplicationContextInitializedEvent 提醒位置
        listeners.contextPrepared(context);
        bootstrapContext.close(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 AbstractAutowireCapableBeanFactory autowireCapableBeanFactory) {
            autowireCapableBeanFactory.setAllowCircularReferences(this.allowCircularReferences);
            if (beanFactory instanceof DefaultListableBeanFactory listableBeanFactory) {
                listableBeanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
            }
        }
        if (this.lazyInitialization) {
            context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
        }
        context.addBeanFactoryPostProcessor(new PropertySourceOrderingBeanFactoryPostProcessor(context));
        if (!AotDetector.useGeneratedArtifacts()) {
            // Load the sources
            Set<Object> sources = getAllSources();
            Assert.notEmpty(sources, "Sources must not be empty");
            load(context, sources.toArray(new Object[0]));
        }
        // 4.ApplicationPreparedEvent 提醒位置
        listeners.contextLoaded(context);
    }

ApplicationStartedEvent

这个事件时在Spring上下文context刷新之后，且在任何application/ command- line runner 被调用之前发送

    public ConfigurableApplicationContext run(String... args) {
        long startTime = System.nanoTime();
        DefaultBootstrapContext bootstrapContext = createBootstrapContext();
        ConfigurableApplicationContext context = null;
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
        listeners.starting(bootstrapContext, this.mainApplicationClass);
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            context.setApplicationStartup(this.applicationStartup);
            prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
            }
      // ApplicationStartedEvent 发布事件位置，从这个方法进入
            listeners.started(context, timeTakenToStartup);
            callRunners(context, applicationArguments);
        }
        catch (Throwable ex) {
            if (ex instanceof AbandonedRunException) {
                throw ex;
            }
            handleRunFailure(context, ex, listeners);
            throw new IllegalStateException(ex);
        }
        try {
            if (context.isRunning()) {
                Duration timeTakenToReady = Duration.ofNanos(System.nanoTime() - startTime);
                listeners.ready(context, timeTakenToReady);
            }
        }
        catch (Throwable ex) {
            if (ex instanceof AbandonedRunException) {
                throw ex;
            }
            handleRunFailure(context, ex, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }

进去看一下listeners.started(context, timeTakenToStartup)方法

@Override
    public void started(ConfigurableApplicationContext context, Duration timeTaken) {
    // ApplicationStartedEvent
        context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context, timeTaken));
    // AvailabilityChangeEvent
        AvailabilityChangeEvent.publish(context, LivenessState.CORRECT);
    }

AvailabilityChangeEvent

这个事件紧随上个事件（ApplicationStartedEvent）之后发送，激活状态ReadinessState.COREECT, 表示应用已处于活动状态。

ApplicationReadyEvent

这个事件在任何application/command- line runners调用之后发送

    public ConfigurableApplicationContext run(String... args) {
        long startTime = System.nanoTime();
        DefaultBootstrapContext bootstrapContext = createBootstrapContext();
        ConfigurableApplicationContext context = null;
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
        listeners.starting(bootstrapContext, this.mainApplicationClass);
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            context.setApplicationStartup(this.applicationStartup);
            prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
            }
            listeners.started(context, timeTakenToStartup);
      // 调用runners的地方
            callRunners(context, applicationArguments);
        }
        catch (Throwable ex) {
            if (ex instanceof AbandonedRunException) {
                throw ex;
            }
            handleRunFailure(context, ex, listeners);
            throw new IllegalStateException(ex);
        }
        try {
            if (context.isRunning()) {
                Duration timeTakenToReady = Duration.ofNanos(System.nanoTime() - startTime);
                // ApplicationReadyEvent发布位置
        listeners.ready(context, timeTakenToReady);
            }
        }
        catch (Throwable ex) {
            if (ex instanceof AbandonedRunException) {
                throw ex;
            }
            handleRunFailure(context, ex, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }

AvailabilityChangeEvent

这个事件紧随上个事件之后发送，激活状态ReadinessState.ACCEPTING_TRAFFIC, 表示应用可以开始准备接受请求了

@Override
    public void ready(ConfigurableApplicationContext context, Duration timeTaken) {
        context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context, timeTaken));
        AvailabilityChangeEvent.publish(context, ReadinessState.ACCEPTING_TRAFFIC);
    }

ApplicationFailedEvent

这个事件在应用启动异常时发送。

    public ConfigurableApplicationContext run(String... args) {
        long startTime = System.nanoTime();
        DefaultBootstrapContext bootstrapContext = createBootstrapContext();
        ConfigurableApplicationContext context = null;
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
        listeners.starting(bootstrapContext, this.mainApplicationClass);
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
            Banner printedBanner = printBanner(environment);
            context = createApplicationContext();
            context.setApplicationStartup(this.applicationStartup);
            prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
            refreshContext(context);
            afterRefresh(context, applicationArguments);
            Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
            }
            listeners.started(context, timeTakenToStartup);
      // 调用runners的地方
            callRunners(context, applicationArguments);
        }
        catch (Throwable ex) {
            if (ex instanceof AbandonedRunException) {
                throw ex;
            }
      // ApplicationFailedEvent发布位置
            handleRunFailure(context, ex, listeners);
            throw new IllegalStateException(ex);
        }
        try {
            if (context.isRunning()) {
                Duration timeTakenToReady = Duration.ofNanos(System.nanoTime() - startTime);
                // ApplicationReadyEvent发布位置
        listeners.ready(context, timeTakenToReady);
            }
        }
        catch (Throwable ex) {
            if (ex instanceof AbandonedRunException) {
                throw ex;
            }
            handleRunFailure(context, ex, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }