接SpringBoot启动时都做了哪些事（三）？后，我们继续分析SpringBoot启动过程流程。
本文我们分析应用上下文刷新以及后置处理。
回顾一下SpringApplication的run方法：
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; }
【1】refreshContext
① refresh
SpringApplication的refreshContext方法。
private void refreshContext(ConfigurableApplicationContext context) { refresh(context); if (this.registerShutdownHook) { try { context.registerShutdownHook(); } catch (AccessControlException ex) { // Not allowed in some environments. } } }
而refresh方法如下所示，最终会走到AbstractApplicationContext的refresh中。本文这里我们不再分析，详情可以参考系列博文：AbstractApplicationContext中refresh方法详解 。
protected void refresh(ApplicationContext applicationContext) { Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext); ((AbstractApplicationContext) applicationContext).refresh(); } // ServletWebServerApplicationContext @Override public final void refresh() throws BeansException, IllegalStateException { try { // 从这里就是实际AbstractApplicationContext的refresh方法，有12个核心流程 super.refresh(); } catch (RuntimeException ex) { stopAndReleaseWebServer(); throw ex; } }
② registerShutdownHook
注册销毁钩子，也就是当容器关闭的时候触发钩子的执行。如下所示，这里获取到一个shutdownHook，然后添加到了ApplicationShutdownHooks的IdentityHashMap hooks;中。
// AbstractApplicationContext @Override public void registerShutdownHook() { if (this.shutdownHook == null) { // No shutdown hook registered yet. this.shutdownHook = new Thread(SHUTDOWN_HOOK_THREAD_NAME) { @Override public void run() { synchronized (startupShutdownMonitor) { doClose(); } } }; Runtime.getRuntime().addShutdownHook(this.shutdownHook); } } String SHUTDOWN_HOOK_THREAD_NAME = "SpringContextShutdownHook";
hutdownHook 本质就是一个线程对象，容器销毁的时候会触发其start执行。本文这里如上代码所示，会触发doClose方法。本文暂不展开分析，另起篇章进行研究。
【2】afterRefresh
如下所示，默认是个空方法。
// SpringApplication protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) { }
然后就是stopWatch的stop，意味着上下文已经创建并刷新完毕。
stopWatch.stop(); if (this.logStartupInfo) { new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch); } // 日志打印，比如下面 Started RecommendApplication in 7470.961 seconds (JVM running for 7500.285)
【3】listener.started
SpringApplicationRunListeners的started方法，本质会触发EventPublishingRunListener的started方法。
void started(ConfigurableApplicationContext context) { for (SpringApplicationRunListener listener : this.listeners) { listener.started(context); } }
最终如下所示，这里会广播ApplicationStartedEvent事件。
@Override public void started(ConfigurableApplicationContext context) { context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context)); }
如下所示，有三种监听器对该事件感兴趣。
RestartApplicationListener BackgroundPreinitializer DelegatingApplicationListener
【4】callRunners
SpringApplication的callRunners方法。如下所示，这里会扫描ApplicationRunner和CommandLineRunner，对其进行排序，然后遍历触发每一个实例的run方法。
private void callRunners(ApplicationContext context, ApplicationArguments args) { List<Object> runners = new ArrayList<>(); runners.addAll(context.getBeansOfType(ApplicationRunner.class).values()); runners.addAll(context.getBeansOfType(CommandLineRunner.class).values()); AnnotationAwareOrderComparator.sort(runners); for (Object runner : new LinkedHashSet<>(runners)) { if (runner instanceof ApplicationRunner) { callRunner((ApplicationRunner) runner, args); } if (runner instanceof CommandLineRunner) { callRunner((CommandLineRunner) runner, args); } } }
如下所示ApplicationRunner 与CommandLineRunner一样，都是功能性接口。自定义服务可以实现该接口，那么在应用启动完毕后会触发服务的run方法执行。
@FunctionalInterface public interface ApplicationRunner { void run(ApplicationArguments args) throws Exception; } @FunctionalInterface public interface CommandLineRunner { void run(String... args) throws Exception; }
【5】listeners.running
SpringApplicationRunListeners的running方法，本质会触发EventPublishingRunListener的running方法。
void running(ConfigurableApplicationContext context) { for (SpringApplicationRunListener listener : this.listeners) { listener.running(context); } }
最终会广播ApplicationReadyEvent事件。
@Override public void running(ConfigurableApplicationContext context) { context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context)); }
有如下五种监听器对ApplicationReadyEvent事件感兴趣。
0 = {RestartApplicationListener@4405} 1 = {SpringApplicationAdminMXBeanRegistrar@11026} 2 = {BackgroundPreinitializer@4410} 3 = {DelegatingApplicationListener@4412} 4 = {DelegatingApplicationListener@9414} 5 = {ConditionEvaluationDeltaLoggingListener@11027}
到此，SpringBoot启动完毕。
