springboot源码----SpringApplicationRunListener

SpringApplicationRunListener 接口的作用主要就是在springboot 启动初始化的过程中可以通过SpringApplicationRunListener接口回调来让用户在启动的各个流程中可以加入自己的逻辑

    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();

在run方法中springboot 通过getRunListeners方法获得SpringApplicationRunListener接口全部的实现类

    private SpringApplicationRunListeners getRunListeners(String[] args) {
        Class[] types = new Class[] { SpringApplication.class, String[].class };
        return new SpringApplicationRunListeners(logger, getSpringFactoriesInstances(
                SpringApplicationRunListener.class, types, this, args));
    }
    private  Collection getSpringFactoriesInstances(Class type,
            Class[] parameterTypes, Object... args) {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        // Use names and ensure unique to protect against duplicates
        Set names = new LinkedHashSet<>(
                SpringFactoriesLoader.loadFactoryNames(type, classLoader));
        List instances = createSpringFactoriesInstances(type, parameterTypes,
                classLoader, args, names);
        AnnotationAwareOrderComparator.sort(instances);
        return instances;
    }

初始化方法和之前一样 也是通过读取spring.factories文件通过反射的机制获取实现类
接下来看下SpringApplicationRunListener接口的定义：

public interface SpringApplicationRunListener {

    /**
     * Called immediately when the run method has first started. Can be used for very
     * early initialization.
     */
    void starting();

    /**
     * Called once the environment has been prepared, but before the
     * {@link ApplicationContext} has been created.
     * @param environment the environment
     */
    void environmentPrepared(ConfigurableEnvironment environment);

    /**
     * Called once the {@link ApplicationContext} has been created and prepared, but
     * before sources have been loaded.
     * @param context the application context
     */
    void contextPrepared(ConfigurableApplicationContext context);

    /**
     * Called once the application context has been loaded but before it has been
     * refreshed.
     * @param context the application context
     */
    void contextLoaded(ConfigurableApplicationContext context);

    /**
     * The context has been refreshed and the application has started but
     * {@link CommandLineRunner CommandLineRunners} and {@link ApplicationRunner
     * ApplicationRunners} have not been called.
     * @param context the application context.
     * @since 2.0.0
     */
    void started(ConfigurableApplicationContext context);

    /**
     * Called immediately before the run method finishes, when the application context has
     * been refreshed and all {@link CommandLineRunner CommandLineRunners} and
     * {@link ApplicationRunner ApplicationRunners} have been called.
     * @param context the application context.
     * @since 2.0.0
     */
    void running(ConfigurableApplicationContext context);

    /**
     * Called when a failure occurs when running the application.
     * @param context the application context or {@code null} if a failure occurred before
     * the context was created
     * @param exception the failure
     * @since 2.0.0
     */
    void failed(ConfigurableApplicationContext context, Throwable exception);

}

• 第一个方法 starting触发时机：

    StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        Collection exceptionReporters = new ArrayList<>();
        configureHeadlessProperty();
        SpringApplicationRunListeners listeners = getRunListeners(args);
        listeners.starting();

这边主要看listeners.starting()

    public void starting() {
        for (SpringApplicationRunListener listener : this.listeners) {
            listener.starting();
        }
    }

这边在spring刚拿到所有的SpringApplicationRunListener实现类后就直接调用了starting 通知各个SpringApplicationRunListener的实现类

• 第二个environmentPrepared触发时间：

private ConfigurableEnvironment prepareEnvironment(
            SpringApplicationRunListeners listeners,
            ApplicationArguments applicationArguments) {
        // Create and configure the environment
        ConfigurableEnvironment environment = getOrCreateEnvironment();
        configureEnvironment(environment, applicationArguments.getSourceArgs());
        listeners.environmentPrepared(environment);
        bindToSpringApplication(environment);
        if (this.webApplicationType == WebApplicationType.NONE) {
            environment = new EnvironmentConverter(getClassLoader())
                    .convertToStandardEnvironmentIfNecessary(environment);
        }
        ConfigurationPropertySources.attach(environment);
        return environment;
    }

在准备好了ConfigurableEnvironment坏境的时候通知各个实现类

• 第三个contextPrepared触发时间：

    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);
        }

在spring 结束applyInitializers后进行通知

• 第四个 contextLoaded 触发时间

    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
        context.getBeanFactory().registerSingleton("springApplicationArguments",
                applicationArguments);
        if (printedBanner != null) {
            context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
        }

        // Load the sources
        Set