SpringBoot源码解析(四)：监听器 springboot源码解析(四)：监听器​ 在看springboot的源码过程中，发现内部使用了大量的监听器，下面来看下监听器的作用。在springboot的监听器有如下两类：# Run Listeners #事件发布运行监听器，是springboot中配置的唯一一个应用运行监听器，作用是通过一个多路广播器，将springboot运行状态的变化，构建成事件，并广播给各个监听器 org.springframework.boot.SpringApplicationRunListener=\ org.springframework.boot.context.event.EventPublishingRunListener # Application Listeners org.springframework.context.ApplicationListener=\ org.springframework.boot.ClearCachesApplicationListener(),\ org.springframework.boot.builder.ParentContextCloserApplicationListener,\ org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\ org.springframework.boot.context.FileEncodingApplicationListener,\ org.springframework.boot.context.config.AnsiOutputApplicationListener,\ org.springframework.boot.context.config.ConfigFileApplicationListener,\ org.springframework.boot.context.config.DelegatingApplicationListener,\ org.springframework.boot.context.logging.ClasspathLoggingApplicationListener,\ org.springframework.boot.context.logging.LoggingApplicationListener,\ org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener # Application Listeners org.springframework.context.ApplicationListener=\ org.springframework.boot.autoconfigure.BackgroundPreinitializer​ 当程序开始运行的时候，可以看到启动了一个运行时监听器，并且创建了一个SpringApplicationRunListeners对象，该对象是一个封装工具类，封装了所有的启动监听器：代码如下class SpringApplicationRunListeners { private final Log log; //启动类监听器 private final List<SpringApplicationRunListener> listeners; SpringApplicationRunListeners(Log log, Collection<? extends SpringApplicationRunListener> listeners) { this.log = log; this.listeners = new ArrayList<>(listeners); } //启动上下文事件监听 void starting() { for (SpringApplicationRunListener listener : this.listeners) { listener.starting(); } } //environment准备完毕事件监听 void environmentPrepared(ConfigurableEnvironment environment) { for (SpringApplicationRunListener listener : this.listeners) { listener.environmentPrepared(environment); } } //spring上下文准备完毕事件监听 void contextPrepared(ConfigurableApplicationContext context) { for (SpringApplicationRunListener listener : this.listeners) { listener.contextPrepared(context); } } //上下文配置类加载事件监听 void contextLoaded(ConfigurableApplicationContext context) { for (SpringApplicationRunListener listener : this.listeners) { listener.contextLoaded(context); } } //上下文刷新调用事件 void started(ConfigurableApplicationContext context) { for (SpringApplicationRunListener listener : this.listeners) { listener.started(context); } } //上下文刷新完成，在run方法执行完之前调用该事件 void running(ConfigurableApplicationContext context) { for (SpringApplicationRunListener listener : this.listeners) { listener.running(context); } } //在运行过程中失败调起的事件 void failed(ConfigurableApplicationContext context, Throwable exception) { for (SpringApplicationRunListener listener : this.listeners) { callFailedListener(listener, context, exception); } } private void callFailedListener(SpringApplicationRunListener listener, ConfigurableApplicationContext context, Throwable exception) { try { listener.failed(context, exception); } catch (Throwable ex) { if (exception == null) { ReflectionUtils.rethrowRuntimeException(ex); } if (this.log.isDebugEnabled()) { this.log.error("Error handling failed", ex); } else { String message = ex.getMessage(); message = (message != null) ? message : "no error message"; this.log.warn("Error handling failed (" + message + ")"); } } } } ​ 在启动源码的流程中，我们知道不同的方法会在不同的时间点触发执行，然后广播出不同的事件，进入到EventPublishingRunListener类中public EventPublishingRunListener(SpringApplication application, String[] args) { this.application = application; this.args = args; this.initialMulticaster = new SimpleApplicationEventMulticaster(); for (ApplicationListener<?> listener : application.getListeners()) { this.initialMulticaster.addApplicationListener(listener); } }​ 在当前类的构造方法中默认创建了SimpleApplicationEventMulticaster类，用来完成创建全局的事件发布功能@Override public void starting() { this.initialMulticaster.multicastEvent(new ApplicationStartingEvent(this.application, this.args)); } @Override public void environmentPrepared(ConfigurableEnvironment environment) { this.initialMulticaster .multicastEvent(new ApplicationEnvironmentPreparedEvent(this.application, this.args, environment)); } @Override public void contextPrepared(ConfigurableApplicationContext context) { this.initialMulticaster .multicastEvent(new ApplicationContextInitializedEvent(this.application, this.args, context)); } @Override public void contextLoaded(ConfigurableApplicationContext context) { for (ApplicationListener<?> listener : this.application.getListeners()) { if (listener instanceof ApplicationContextAware) { ((ApplicationContextAware) listener).setApplicationContext(context); } context.addApplicationListener(listener); } this.initialMulticaster.multicastEvent(new ApplicationPreparedEvent(this.application, this.args, context)); } @Override public void started(ConfigurableApplicationContext context) { context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context)); } @Override public void running(ConfigurableApplicationContext context) { context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context)); } @Override public void failed(ConfigurableApplicationContext context, Throwable exception) { ApplicationFailedEvent event = new ApplicationFailedEvent(this.application, this.args, context, exception); if (context != null && context.isActive()) { // Listeners have been registered to the application context so we should // use it at this point if we can context.publishEvent(event); } else { // An inactive context may not have a multicaster so we use our multicaster to // call all of the context's listeners instead if (context instanceof AbstractApplicationContext) { for (ApplicationListener<?> listener : ((AbstractApplicationContext) context) .getApplicationListeners()) { this.initialMulticaster.addApplicationListener(listener); } } this.initialMulticaster.setErrorHandler(new LoggingErrorHandler()); this.initialMulticaster.multicastEvent(event); } }​ 在进行事件广播的时候，会进入如下方法：@Override public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) { ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event)); //获取线程池 Executor executor = getTaskExecutor(); //根据事件类型选取需要通知的监听器 for (ApplicationListener<?> listener : getApplicationListeners(event, type)) { //如果不为空，则异步执行 if (executor != null) { executor.execute(() -> invokeListener(listener, event)); } else { //如果为空，则同步执行 invokeListener(listener, event); } } }​ 在进行事件广播之前，需要将监听器进行过滤，符合类型的留下，不符合类型的过滤掉protected Collection<ApplicationListener<?>> getApplicationListeners( ApplicationEvent event, ResolvableType eventType) { Object source = event.getSource(); Class<?> sourceType = (source != null ? source.getClass() : null); ListenerCacheKey cacheKey = new ListenerCacheKey(eventType, sourceType); // Quick check for existing entry on ConcurrentHashMap... ListenerRetriever retriever = this.retrieverCache.get(cacheKey); if (retriever != null) { return retriever.getApplicationListeners(); } if (this.beanClassLoader == null || (ClassUtils.isCacheSafe(event.getClass(), this.beanClassLoader) && (sourceType == null || ClassUtils.isCacheSafe(sourceType, this.beanClassLoader)))) { // Fully synchronized building and caching of a ListenerRetriever synchronized (this.retrievalMutex) { retriever = this.retrieverCache.get(cacheKey); if (retriever != null) { return retriever.getApplicationListeners(); } retriever = new ListenerRetriever(true); Collection<ApplicationListener<?>> listeners = retrieveApplicationListeners(eventType, sourceType, retriever); this.retrieverCache.put(cacheKey, retriever); return listeners; } } else { // No ListenerRetriever caching -> no synchronization necessary return retrieveApplicationListeners(eventType, sourceType, null); } }​ 实际处理判断逻辑的类：private Collection<ApplicationListener<?>> retrieveApplicationListeners( ResolvableType eventType, @Nullable Class<?> sourceType, @Nullable ListenerRetriever retriever) { List<ApplicationListener<?>> allListeners = new ArrayList<>(); Set<ApplicationListener<?>> listeners; Set<String> listenerBeans; synchronized (this.retrievalMutex) { listeners = new LinkedHashSet<>(this.defaultRetriever.applicationListeners); listenerBeans = new LinkedHashSet<>(this.defaultRetriever.applicationListenerBeans); } // Add programmatically registered listeners, including ones coming // from ApplicationListenerDetector (singleton beans and inner beans). for (ApplicationListener<?> listener : listeners) { if (supportsEvent(listener, eventType, sourceType)) { if (retriever != null) { retriever.applicationListeners.add(listener); } allListeners.add(listener); } } // Add listeners by bean name, potentially overlapping with programmatically // registered listeners above - but here potentially with additional metadata. if (!listenerBeans.isEmpty()) { ConfigurableBeanFactory beanFactory = getBeanFactory(); for (String listenerBeanName : listenerBeans) { try { if (supportsEvent(beanFactory, listenerBeanName, eventType)) { ApplicationListener<?> listener = beanFactory.getBean(listenerBeanName, ApplicationListener.class); if (!allListeners.contains(listener) && supportsEvent(listener, eventType, sourceType)) { if (retriever != null) { if (beanFactory.isSingleton(listenerBeanName)) { retriever.applicationListeners.add(listener); } else { retriever.applicationListenerBeans.add(listenerBeanName); } } allListeners.add(listener); } } else { // Remove non-matching listeners that originally came from // ApplicationListenerDetector, possibly ruled out by additional // BeanDefinition metadata (e.g. factory method generics) above. Object listener = beanFactory.getSingleton(listenerBeanName); if (retriever != null) { retriever.applicationListeners.remove(listener); } allListeners.remove(listener); } } catch (NoSuchBeanDefinitionException ex) { // Singleton listener instance (without backing bean definition) disappeared - // probably in the middle of the destruction phase } } } AnnotationAwareOrderComparator.sort(allListeners); if (retriever != null && retriever.applicationListenerBeans.isEmpty()) { retriever.applicationListeners.clear(); retriever.applicationListeners.addAll(allListeners); } return allListeners; }在监听器实例化之前，检查是否符合固定的类型 protected boolean supportsEvent( ApplicationListener<?> listener, ResolvableType eventType, @Nullable Class<?> sourceType) { //判断监听器是否是GenericApplicationListener子类，如不是返回一个GenericApplicationListenerAdapter GenericApplicationListener smartListener = (listener instanceof GenericApplicationListener ? (GenericApplicationListener) listener : new GenericApplicationListenerAdapter(listener)); return (smartListener.supportsEventType(eventType) && smartListener.supportsSourceType(sourceType)); }public interface GenericApplicationListener extends ApplicationListener<ApplicationEvent>, Ordered { boolean supportsEventType(ResolvableType eventType); default boolean supportsSourceType(@Nullable Class<?> sourceType) { return true; } @Override default int getOrder() { return LOWEST_PRECEDENCE; } }此时可以看到GenericApplicationListener类，该类是spring提供的用于重写匹配监听器事件的接口，如果需要判断的监听器是GenericApplicationListener的子类，说明类型匹配方法已被重现，就调用子类的匹配方法，如果不是，提供一个默认的适配器来匹配GenericApplicationListenerAdapter public boolean supportsEventType(ResolvableType eventType) { if (this.delegate instanceof SmartApplicationListener) { Class<? extends ApplicationEvent> eventClass = (Class<? extends ApplicationEvent>) eventType.resolve(); return (eventClass != null && ((SmartApplicationListener) this.delegate).supportsEventType(eventClass)); } else { return (this.declaredEventType == null || this.declaredEventType.isAssignableFrom(eventType)); } }可以看到该类最终调用的是declaredEventType.isAssignableFrom(eventType)方法，也就是说，如果我们没有重写监听器匹配方法，那么发布的事件 event 会被监听 event以及监听event的父类的监听器监听到。

SpringBoot源码解析(三)：SpringBoot内嵌Tomcat springboot源码解析(三)：springboot内嵌tomcat​ 在使用springboot搭建一个web应用程序的时候，我们发现不需要自己搭建一个tomcat服务器，只需要引入spring-boot-starter-web,在应用启动时会自动启动嵌入式的tomcat作为服务器，下面来分析下源码的分析流程： ​ 之前我们已经讲过了自动装配的原理，其实tomcat的实现机制也是从自动装配开始的。1、ServletWebServerFactoryAutoConfiguration类@Configuration(proxyBeanMethods = false) @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE) @ConditionalOnClass(ServletRequest.class) @ConditionalOnWebApplication(type = Type.SERVLET) @EnableConfigurationProperties(ServerProperties.class) @Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class, ServletWebServerFactoryConfiguration.EmbeddedTomcat.class, ServletWebServerFactoryConfiguration.EmbeddedJetty.class, ServletWebServerFactoryConfiguration.EmbeddedUndertow.class }) public class ServletWebServerFactoryAutoConfiguration { @Bean public ServletWebServerFactoryCustomizer servletWebServerFactoryCustomizer(ServerProperties serverProperties) { return new ServletWebServerFactoryCustomizer(serverProperties); } @Bean @ConditionalOnClass(name = "org.apache.catalina.startup.Tomcat") public TomcatServletWebServerFactoryCustomizer tomcatServletWebServerFactoryCustomizer( ServerProperties serverProperties) { return new TomcatServletWebServerFactoryCustomizer(serverProperties); } @Bean @ConditionalOnMissingFilterBean(ForwardedHeaderFilter.class) @ConditionalOnProperty(value = "server.forward-headers-strategy", havingValue = "framework") public FilterRegistrationBean<ForwardedHeaderFilter> forwardedHeaderFilter() { ForwardedHeaderFilter filter = new ForwardedHeaderFilter(); FilterRegistrationBean<ForwardedHeaderFilter> registration = new FilterRegistrationBean<>(filter); registration.setDispatcherTypes(DispatcherType.REQUEST, DispatcherType.ASYNC, DispatcherType.ERROR); registration.setOrder(Ordered.HIGHEST_PRECEDENCE); return registration; } /** * Registers a {@link WebServerFactoryCustomizerBeanPostProcessor}. Registered via * {@link ImportBeanDefinitionRegistrar} for early registration. */ public static class BeanPostProcessorsRegistrar implements ImportBeanDefinitionRegistrar, BeanFactoryAware { private ConfigurableListableBeanFactory beanFactory; @Override public void setBeanFactory(BeanFactory beanFactory) throws BeansException { if (beanFactory instanceof ConfigurableListableBeanFactory) { this.beanFactory = (ConfigurableListableBeanFactory) beanFactory; } } @Override public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) { if (this.beanFactory == null) { return; } registerSyntheticBeanIfMissing(registry, "webServerFactoryCustomizerBeanPostProcessor", WebServerFactoryCustomizerBeanPostProcessor.class); registerSyntheticBeanIfMissing(registry, "errorPageRegistrarBeanPostProcessor", ErrorPageRegistrarBeanPostProcessor.class); } private void registerSyntheticBeanIfMissing(BeanDefinitionRegistry registry, String name, Class<?> beanClass) { if (ObjectUtils.isEmpty(this.beanFactory.getBeanNamesForType(beanClass, true, false))) { RootBeanDefinition beanDefinition = new RootBeanDefinition(beanClass); beanDefinition.setSynthetic(true); registry.registerBeanDefinition(name, beanDefinition); } } } } 从这个类上可以看到，当前配置类主要导入了BeanPostProcessorRegister,该类实现了ImportBeanDefinitionRegister接口，可以用来注册额外的BeanDefinition，同时，该类还导入了EmbeddedTomcat，EmbeddedJetty，EmbeddedUndertow三个类，可以根据用户的需求去选择使用哪一个web服务器，默认情况下使用的是tomcat2、当自动装配功能完成之后会接着执行onRefresh的方法（ServletWebServerApplicationContext）@Override protected void onRefresh() { //创建主题对象，不用在意 super.onRefresh(); try { //开始创建web服务 createWebServer(); } catch (Throwable ex) { throw new ApplicationContextException("Unable to start web server", ex); } }3、创建web服务，默认获取的是tomcat的web容器（ServletWebServerApplicationContext）private void createWebServer() { WebServer webServer = this.webServer; ServletContext servletContext = getServletContext(); if (webServer == null && servletContext == null) { //获取servletWebServerFactory,从上下文注册bean中可以找到 ServletWebServerFactory factory = getWebServerFactory(); //获取servletContextInitializer,获取webServer this.webServer = factory.getWebServer(getSelfInitializer()); } else if (servletContext != null) { try { getSelfInitializer().onStartup(servletContext); } catch (ServletException ex) { throw new ApplicationContextException("Cannot initialize servlet context", ex); } } //替换servlet相关的属性资源 initPropertySources(); }如何获取tomcat的bean的实例对象呢？从如下代码中可以看出ServletWebServerApplicationContextprotected ServletWebServerFactory getWebServerFactory() { // Use bean names so that we don't consider the hierarchy String[] beanNames = getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class); if (beanNames.length == 0) { throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to missing " + "ServletWebServerFactory bean."); } if (beanNames.length > 1) { throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to multiple " + "ServletWebServerFactory beans : " + StringUtils.arrayToCommaDelimitedString(beanNames)); } return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class); }protected ServletWebServerFactory getWebServerFactory() { // Use bean names so that we don't consider the hierarchy String[] beanNames = getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class); if (beanNames.length == 0) { throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to missing " + "ServletWebServerFactory bean."); } if (beanNames.length > 1) { throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to multiple " + "ServletWebServerFactory beans : " + StringUtils.arrayToCommaDelimitedString(beanNames)); } return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class); }DefaultListableBeanFactoryf/* 第一个参数type表示要查找的类型 第二个参数表示是否考虑非单例bean 第三个参数表示是否允许提早初始化 */ @Override public String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) { //配置还未被冻结或者类型为null或者不允许早期初始化 if (!isConfigurationFrozen() || type == null || !allowEagerInit) { return doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, allowEagerInit); } //此处注意isConfigurationFrozen为false的时候表示beanDefinition可能还会发生更改和添加，所以不能进行缓存，如果允许非单例bean，那么从保存所有bean的集合中获取，否则从单例bean中获取 Map<Class<?>, String[]> cache = (includeNonSingletons ? this.allBeanNamesByType : this.singletonBeanNamesByType); String[] resolvedBeanNames = cache.get(type); if (resolvedBeanNames != null) { return resolvedBeanNames; } //如果缓存中没有获取到，那么只能重新获取，获取到之后就存入缓存 resolvedBeanNames = doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, true); if (ClassUtils.isCacheSafe(type, getBeanClassLoader())) { cache.put(type, resolvedBeanNames); } return resolvedBeanNames; } private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) { List<String> result = new ArrayList<>(); // Check all bean definitions. for (String beanName : this.beanDefinitionNames) { // Only consider bean as eligible if the bean name // is not defined as alias for some other bean. //如果时别名则跳过（当前集合会保存所有的主beanname，并且不会保存别名，别名由beanfactory中别名map维护） if (!isAlias(beanName)) { try { //获取合并的beandefinition，合并的beandefinition是指spring整合了父beandefinition的属性，将其beandefinition编程了rootBeanDefinition RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); // Only check bean definition if it is complete. //抽象的beandefinition是不做考虑，抽象的就是拿来继承的，如果允许早期初始化，那么直接短路，进入方法体，如果不允许早期初始化，那么需要进一步判断，如果是不允许早期初始化的，并且beanClass已经被加载或者它是可以早期初始化的，那么如果当前bean是工厂bean，并且指定的bean又是工厂那么这个bean就必须被早期初始化，也就是说就不符合我们制定的allowEagerInit为false的情况，直接跳过 if (!mbd.isAbstract() && (allowEagerInit || (mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading()) && !requiresEagerInitForType(mbd.getFactoryBeanName()))) { //如果当前bean是工厂bean boolean isFactoryBean = isFactoryBean(beanName, mbd); //如果允许早期初始化，那么基本上会调用最后的isTypeMatch方法，这个方法会导致工厂的实例化，但是当前不允许进行早期实例化在不允许早期实例化的情况下，如果当前bean是工厂bean，那么它只能在已经被创建的情况下调用isTypeMatch进行匹配判断否则只能宣告匹配失败，返回false BeanDefinitionHolder dbd = mbd.getDecoratedDefinition(); boolean matchFound = false; boolean allowFactoryBeanInit = allowEagerInit || containsSingleton(beanName); boolean isNonLazyDecorated = dbd != null && !mbd.isLazyInit(); if (!isFactoryBean) { if (includeNonSingletons || isSingleton(beanName, mbd, dbd)) { matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit); } } else { //如果没有匹配到并且他是个工厂bean，那么加上&前缀，表示要获取factorybean类型的bean if (includeNonSingletons || isNonLazyDecorated || (allowFactoryBeanInit && isSingleton(beanName, mbd, dbd))) { matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit); } if (!matchFound) { // In case of FactoryBean, try to match FactoryBean instance itself next. beanName = FACTORY_BEAN_PREFIX + beanName; matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit); } } //找到便记录到result集合中，等待返回 if (matchFound) { result.add(beanName); } } } catch (CannotLoadBeanClassException | BeanDefinitionStoreException ex) { if (allowEagerInit) { throw ex; } // Probably a placeholder: let's ignore it for type matching purposes. LogMessage message = (ex instanceof CannotLoadBeanClassException) ? LogMessage.format("Ignoring bean class loading failure for bean '%s'", beanName) : LogMessage.format("Ignoring unresolvable metadata in bean definition '%s'", beanName); logger.trace(message, ex); onSuppressedException(ex); } } } // Check manually registered singletons too. //从单例注册集合中获取，这个单例集合石保存spring内部注入的单例对象，他们的特点就是没有beanDefinition for (String beanName : this.manualSingletonNames) { try { // In case of FactoryBean, match object created by FactoryBean. //如果是工厂bean,那么调用其getObjectType去匹配是否符合指定类型 if (isFactoryBean(beanName)) { if ((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)) { result.add(beanName); // Match found for this bean: do not match FactoryBean itself anymore. continue; } // In case of FactoryBean, try to match FactoryBean itself next. beanName = FACTORY_BEAN_PREFIX + beanName; } // Match raw bean instance (might be raw FactoryBean). //如果没有匹配成功，那么匹配工厂类 if (isTypeMatch(beanName, type)) { result.add(beanName); } } catch (NoSuchBeanDefinitionException ex) { // Shouldn't happen - probably a result of circular reference resolution... logger.trace(LogMessage.format("Failed to check manually registered singleton with name '%s'", beanName), ex); } } return StringUtils.toStringArray(result); }4、tomcat对象的初始化（ServletWebServerApplicationContext）private org.springframework.boot.web.servlet.ServletContextInitializer getSelfInitializer() { return this::selfInitialize; } private void selfInitialize(ServletContext servletContext) throws ServletException { //使用给定的完全加载的servletContext准备WebApplicationContext prepareWebApplicationContext(servletContext); registerApplicationScope(servletContext); //使用给定的BeanFactory注册特定于web的作用域bean（contextParameters,contextAttributes） WebApplicationContextUtils.registerEnvironmentBeans(getBeanFactory(), servletContext); for (ServletContextInitializer beans : getServletContextInitializerBeans()) { beans.onStartup(servletContext); } }5、完成内嵌tomcat的api调用（TomcatServletWebServerFactory）@Override public WebServer getWebServer(ServletContextInitializer... initializers) { if (this.disableMBeanRegistry) { Registry.disableRegistry(); } //完成tomcat的api调用 Tomcat tomcat = new Tomcat(); File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat"); tomcat.setBaseDir(baseDir.getAbsolutePath()); Connector connector = new Connector(this.protocol); connector.setThrowOnFailure(true); tomcat.getService().addConnector(connector); customizeConnector(connector); tomcat.setConnector(connector); tomcat.getHost().setAutoDeploy(false); configureEngine(tomcat.getEngine()); for (Connector additionalConnector : this.additionalTomcatConnectors) { tomcat.getService().addConnector(additionalConnector); } //准备tomcatEmbeddedContext并设置到tomcat中 prepareContext(tomcat.getHost(), initializers); //构建tomcatWebServer return getTomcatWebServer(tomcat); }6、获取tomcat服务（TomcatServletWebServerFactory）protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) { return new TomcatWebServer(tomcat, getPort() >= 0); } public TomcatWebServer(Tomcat tomcat, boolean autoStart) { Assert.notNull(tomcat, "Tomcat Server must not be null"); this.tomcat = tomcat; this.autoStart = autoStart; //初始化 initialize(); }7、完成tomcat的初始化private void initialize() throws WebServerException { logger.info("Tomcat initialized with port(s): " + getPortsDescription(false)); synchronized (this.monitor) { try { //engineName拼接instanceId addInstanceIdToEngineName(); Context context = findContext(); context.addLifecycleListener((event) -> { if (context.equals(event.getSource()) && Lifecycle.START_EVENT.equals(event.getType())) { // Remove service connectors so that protocol binding doesn't // happen when the service is started. //删除Connectors，以便再启动服务时不发生协议绑定 removeServiceConnectors(); } }); // Start the server to trigger initialization listeners //启动服务触发初始化监听器 this.tomcat.start(); // We can re-throw failure exception directly in the main thread //在主线程中重新抛出失败异常 rethrowDeferredStartupExceptions(); try { ContextBindings.bindClassLoader(context, context.getNamingToken(), getClass().getClassLoader()); } catch (NamingException ex) { // Naming is not enabled. Continue } // Unlike Jetty, all Tomcat threads are daemon threads. We create a // blocking non-daemon to stop immediate shutdown //所有的tomcat线程都是守护线程，我们创建一个阻塞非守护线程来避免立即关闭 startDaemonAwaitThread(); } catch (Exception ex) { //异常停止tomcat stopSilently(); destroySilently(); throw new WebServerException("Unable to start embedded Tomcat", ex); } } } ----------------------- private void removeServiceConnectors() { for (Service service : this.tomcat.getServer().findServices()) { Connector[] connectors = service.findConnectors().clone(); //将将要移除的conntector放到缓存中暂存 this.serviceConnectors.put(service, connectors); for (Connector connector : connectors) { //移除connector service.removeConnector(connector); } } }8、除了refresh方法之外，在finishRefresh()方法中也对tomcat做了相关的处理（ServletWebServerApplicationContext） protected void finishRefresh() { //调用父类的finishRefresh方法 super.finishRefresh(); //启动webServer WebServer webServer = startWebServer(); if (webServer != null) { //发布webServer初始化完成事件 publishEvent(new ServletWebServerInitializedEvent(webServer, this)); } }ServletWebServerApplicationContext private WebServer startWebServer() { WebServer webServer = this.webServer; if (webServer != null) { //启动webserver webServer.start(); } return webServer; }TomcatWebServer public void start() throws WebServerException { synchronized (this.monitor) { if (this.started) { return; } try { //添加之前移除的connector addPreviouslyRemovedConnectors(); Connector connector = this.tomcat.getConnector(); if (connector != null && this.autoStart) { //延迟加载启动 performDeferredLoadOnStartup(); } //检查connector启动状态是否为失败，失败抛出异常 checkThatConnectorsHaveStarted(); this.started = true; logger.info("Tomcat started on port(s): " + getPortsDescription(true) + " with context path '" + getContextPath() + "'"); } catch (ConnectorStartFailedException ex) { //异常停止tomcat stopSilently(); throw ex; } catch (Exception ex) { if (findBindException(ex) != null) { throw new PortInUseException(this.tomcat.getConnector().getPort()); } throw new WebServerException("Unable to start embedded Tomcat server", ex); } finally { Context context = findContext(); //context解绑classload ContextBindings.unbindClassLoader(context, context.getNamingToken(), getClass().getClassLoader()); } } }private void addPreviouslyRemovedConnectors() { Service[] services = this.tomcat.getServer().findServices(); for (Service service : services) { //从上面移除connector添加的缓存中取出connector Connector[] connectors = this.serviceConnectors.get(service); if (connectors != null) { for (Connector connector : connectors) { //添加到tomcat service中 service.addConnector(connector); if (!this.autoStart) { //如果不是自动启动，则暂停connector stopProtocolHandler(connector); } } //添加完成后移除 this.serviceConnectors.remove(service); } } }private void performDeferredLoadOnStartup() { try { for (Container child : this.tomcat.getHost().findChildren()) { if (child instanceof TomcatEmbeddedContext) { //延迟加载启动 ((TomcatEmbeddedContext) child).deferredLoadOnStartup(); } } } catch (Exception ex) { if (ex instanceof WebServerException) { throw (WebServerException) ex; } throw new WebServerException("Unable to start embedded Tomcat connectors", ex); } } void deferredLoadOnStartup() throws LifecycleException { doWithThreadContextClassLoader(getLoader().getClassLoader(), () -> getLoadOnStartupWrappers(findChildren()).forEach(this::load)); }9、应用上下文关闭时会调用tomcat的关闭在refreshContext中注册一个关闭的钩子函数，而钩子函数可以完成关闭的功能ServletWebServerApplicationContext @Override protected void onClose() { super.onClose(); stopAndReleaseWebServer(); } private void stopAndReleaseWebServer() { WebServer webServer = this.webServer; if (webServer != null) { try { webServer.stop(); this.webServer = null; } catch (Exception ex) { throw new IllegalStateException(ex); } } }TomcatWebServer@Override public void stop() throws WebServerException { synchronized (this.monitor) { boolean wasStarted = this.started; try { this.started = false; try { stopTomcat(); this.tomcat.destroy(); } catch (LifecycleException ex) { // swallow and continue } } catch (Exception ex) { throw new WebServerException("Unable to stop embedded Tomcat", ex); } finally { if (wasStarted) { containerCounter.decrementAndGet(); } } } }

Spring的自动配置原理 spring的自动配置原理springboot配置文件的装配过程1、springboot在启动的时候会加载主配置类，开启了@EnableAutoConfiguration。2、@EnableAutoConfiguration的作用：利用AutoConfigurationImportSelector给容器导入一些组件。查看selectImports方法的内容，返回一个AutoConfigurationEntryAutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(autoConfigurationMetadata, annotationMetadata); ------ List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes); ------ protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) { List<String> configurations = SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader()); Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you " + "are using a custom packaging, make sure that file is correct."); return configurations; }可以看到SpringFactoriesLoader.loadFactoryNames，继续看又调用了loadSpringFactories方法，获取META-INF/spring.factories资源文件public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) { String factoryTypeName = factoryType.getName(); return loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList()); } private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) { MultiValueMap<String, String> result = cache.get(classLoader); if (result != null) { return result; } try { Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) : ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION)); result = new LinkedMultiValueMap<>(); while (urls.hasMoreElements()) { URL url = urls.nextElement(); UrlResource resource = new UrlResource(url); Properties properties = PropertiesLoaderUtils.loadProperties(resource); for (Map.Entry<?, ?> entry : properties.entrySet()) { String factoryTypeName = ((String) entry.getKey()).trim(); for (String factoryImplementationName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) { result.add(factoryTypeName, factoryImplementationName.trim()); } } } cache.put(classLoader, result); return result; } catch (IOException ex) { throw new IllegalArgumentException("Unable to load factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex); } }总结：将类路径下 META-INF/spring.factories 里面配置的所有EnableAutoConfiguration的值加入到了容器中；每一个xxxAutoConfiguration类都是容器中的一个组件，最后都加入到容器中，用来做自动配置，每一个自动配置类都可以进行自动配置功能使用HttpEncodingAutoConfiguration来解释自动装配原理/* 表名这是一个配置类， */ @Configuration(proxyBeanMethods = false) /* 启动指定类的ConfigurationProperties功能,进入HttpProperties查看，将配置文件中对应的值和HttpProperties绑定起来，并把HttpProperties加入到ioc容器中 */ @EnableConfigurationProperties(HttpProperties.class) /* spring底层@Confitional注解，根据不同的条件判断，如果满足指定的条件，整个配置类里面的配置就会生效 此时表示判断当前应用是否是web应用，如果是，那么配置类生效 */ @ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.SERVLET) /* 判断当前项目由没有这个类CharacterEncodingFilter，springmvc中进行乱码解决的过滤器 */ @ConditionalOnClass(CharacterEncodingFilter.class) /* 判断配置文件中是否存在某个配置：spring.http.encoding.enabled 如果不存在，判断也是成立的， 即使我们配置文件中不配置spring.http.encoding.enabled=true，也是默认生效的 */ @ConditionalOnProperty(prefix = "spring.http.encoding", value = "enabled", matchIfMissing = true) public class HttpEncodingAutoConfiguration { //和springboot的配置文件映射 private final HttpProperties.Encoding properties; //只有一个有参构造器的情况下，参数的值就会从容器中拿 public HttpEncodingAutoConfiguration(HttpProperties properties) { this.properties = properties.getEncoding(); } //给容器中添加一个组件，这个组件的某些值需要从properties中获取 @Bean @ConditionalOnMissingBean//判断容器中是否有此组件 public CharacterEncodingFilter characterEncodingFilter() { CharacterEncodingFilter filter = new OrderedCharacterEncodingFilter(); filter.setEncoding(this.properties.getCharset().name()); filter.setForceRequestEncoding(this.properties.shouldForce(Type.REQUEST)); filter.setForceResponseEncoding(this.properties.shouldForce(Type.RESPONSE)); return filter; } @Bean public LocaleCharsetMappingsCustomizer localeCharsetMappingsCustomizer() { return new LocaleCharsetMappingsCustomizer(this.properties); } private static class LocaleCharsetMappingsCustomizer implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory>, Ordered { private final HttpProperties.Encoding properties; LocaleCharsetMappingsCustomizer(HttpProperties.Encoding properties) { this.properties = properties; } @Override public void customize(ConfigurableServletWebServerFactory factory) { if (this.properties.getMapping() != null) { factory.setLocaleCharsetMappings(this.properties.getMapping()); } } @Override public int getOrder() { return 0; } } } 根据当前不同的条件判断，决定这个配置类是否生效！总结：​ 1、springboot启动会加载大量的自动配置类​ 2、查看需要的功能有没有在springboot默认写好的自动配置类中华​ 3、查看这个自动配置类到底配置了哪些组件​ 4、给容器中自动配置类添加组件的时候，会从properties类中获取属性@Conditional：自动配置类在一定条件下才能生效@Conditional扩展注解作用@ConditionalOnJava系统的java版本是否符合要求@ConditionalOnBean容器中存在指定Bean@ConditionalOnMissingBean容器中不存在指定Bean@ConditionalOnExpression满足SpEL表达式@ConditionalOnClass系统中有指定的类@ConditionalOnMissingClass系统中没有指定的类@ConditionalOnSingleCandidate容器中只有一个指定的Bean，或者是首选Bean@ConditionalOnProperty系统中指定的属性是否有指定的值@ConditionalOnResource类路径下是否存在指定资源文件@ConditionOnWebApplication当前是web环境@ConditionalOnNotWebApplication当前不是web环境@ConditionalOnJndiJNDI存在指定项

SpringBoot运行原理 springboot运行原理1、启动器<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency>​ springboot-boot-starter:就是springboot的场景启动器。springboot将所有的功能场景都抽取出来，做成一个个的starter，只需要在项目中引入这些starter即可，所有相关的依赖都会导入进来，根据公司业务需求决定导入什么启动器即可。2、主程序package com.mashibing; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; //SpringBootApplication注解用来标注一个主程序类，说明是一个springboot应用 @SpringBootApplication public class StudyApplication { public static void main(String[] args) { SpringApplication.run(StudyApplication.class, args); } }查看@SpringBootApplication/* @ComponentScan:自动扫描并加载符合条件的组件或者bean，将这个bean定义加载到IOC容器中 @SpringBootConfiguration:标注在某个类上，表示这是一个springboot的配置类。 @EnableAutoConfiguration:开启自动配置功能,之前在使用springboot的时候，springboot可以自动帮我们完成配置功能，@EnableAutoConfiguration告诉springboot开启自动配置功能，这样自动配置才能生效 */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) }) public @interface SpringBootApplication {}/* 可以看到SpringBootConfiguration使用了Configuration注解来标注 */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Configuration public @interface SpringBootConfiguration {}/* 可以看到Configuration也是容器中的一个组件 */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Component public @interface Configuration {}/* @AutoConfigurationPackage:自动配置包 @Import(AutoConfigurationImportSelector.class)：导入哪些组件的选择器，它将所有需要导入的组件以全类名的方式返回，这些组件就会被添加到容器中，它会给容器中导入非常多的自动配置类，就是给容器中导入这个场景需要的所有组件，并配置好这些组件 */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @AutoConfigurationPackage @Import(AutoConfigurationImportSelector.class) public @interface EnableAutoConfiguration {}/* 给容器导入一个组件，导入的组件由AutoConfigurationPackages.Registrar.class将主配置类（@SpringBootApplication标注的类）的所在包及包下面所有子包里面的所有组件扫描到spring容器 */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @Import(AutoConfigurationPackages.Registrar.class) public @interface AutoConfigurationPackage {}/* 在AutoConfigurationImportSelector类中有如下方法，可以看到 */ protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) { List<String> configurations = SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader()); Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you " + "are using a custom packaging, make sure that file is correct."); return configurations; } /* 此时返回的就是启动自动导入配置文件的注解类 */ protected Class<?> getSpringFactoriesLoaderFactoryClass() { return EnableAutoConfiguration.class; } //进入SpringFactoriesLoader类中 /* 看到会读取对应的配置文件，位置在META-INF/spring.factories中 */ public final class SpringFactoriesLoader { /** * The location to look for factories. * <p>Can be present in multiple JAR files. */ public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";} //进入loadFactoryNames方法中 public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) { String factoryTypeName = factoryType.getName(); return loadSpringFactories(classLoader).getOrDefault(factoryTypeName, Collections.emptyList()); } private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) { MultiValueMap<String, String> result = cache.get(classLoader); if (result != null) { return result; } try { Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) : ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION)); result = new LinkedMultiValueMap<>(); while (urls.hasMoreElements()) { URL url = urls.nextElement(); UrlResource resource = new UrlResource(url); Properties properties = PropertiesLoaderUtils.loadProperties(resource); for (Map.Entry<?, ?> entry : properties.entrySet()) { String factoryTypeName = ((String) entry.getKey()).trim(); for (String factoryImplementationName : StringUtils.commaDelimitedListToStringArray((String) entry.getValue())) { result.add(factoryTypeName, factoryImplementationName.trim()); } } } cache.put(classLoader, result); return result; } catch (IOException ex) { throw new IllegalArgumentException("Unable to load factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex); } }springboot在启动的时候从类路径下的META-INF/spring.factories中获取EnableAutoConfiguration指定的值，将这些值作为自动配置类导入容器，自动配置类就生效，帮我们进行自动配置的工作：spring.factories文件位于springboot-autoconfigure.jar包中。所以真正实现是从classpath中搜寻所有的META-INF/spring.factories配置文件，并将其中对应org.springframework.boot.autoconfigure.包下的配置项通过反射实例化为对应标注了@Configuration的JavaConfig形式的IOC容器配置类，然后将这些都汇总称为一个实例并加载到IOC容器中。

SpringBoot源码(二)：自动装配原理 springboot源码(二)：自动装配原理​ 在之前的课程中我们讲解了springboot的启动过程，其实在面试过程中问的最多的可能是自动装配的原理，而自动装配是在启动过程中完成，只不过在刚开始的时候我们选择性的跳过了，下面详细讲解自动装配的过程。1、在springboot的启动过程中，有一个步骤是创建上下文，如果不记得可以看下面的代码：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); //此处完成自动装配的过程 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; }2、在prepareContext方法中查找load方法，一层一层向内点击，找到最终的load方法//prepareContext方法 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<Object> sources = getAllSources(); Assert.notEmpty(sources, "Sources must not be empty"); //load方法完成该功能 load(context, sources.toArray(new Object[0])); listeners.contextLoaded(context); } /** * Load beans into the application context. * @param context the context to load beans into * @param sources the sources to load * 加载bean对象到context中 */ protected void load(ApplicationContext context, Object[] sources) { if (logger.isDebugEnabled()) { logger.debug("Loading source " + StringUtils.arrayToCommaDelimitedString(sources)); } //获取bean对象定义的加载器 BeanDefinitionLoader loader = createBeanDefinitionLoader(getBeanDefinitionRegistry(context), sources); if (this.beanNameGenerator != null) { loader.setBeanNameGenerator(this.beanNameGenerator); } if (this.resourceLoader != null) { loader.setResourceLoader(this.resourceLoader); } if (this.environment != null) { loader.setEnvironment(this.environment); } loader.load(); } /** * Load the sources into the reader. * @return the number of loaded beans */ int load() { int count = 0; for (Object source : this.sources) { count += load(source); } return count; }3、实际执行load的是BeanDefinitionLoader中的load方法，如下： //实际记载bean的方法 private int load(Object source) { Assert.notNull(source, "Source must not be null"); //如果是class类型，启用注解类型 if (source instanceof Class<?>) { return load((Class<?>) source); } //如果是resource类型，启动xml解析 if (source instanceof Resource) { return load((Resource) source); } //如果是package类型，启用扫描包，例如@ComponentScan if (source instanceof Package) { return load((Package) source); } //如果是字符串类型，直接加载 if (source instanceof CharSequence) { return load((CharSequence) source); } throw new IllegalArgumentException("Invalid source type " + source.getClass()); }4、下面方法将用来判断是否资源的类型，是使用groovy加载还是使用注解的方式 private int load(Class<?> source) { //判断使用groovy脚本 if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) { // Any GroovyLoaders added in beans{} DSL can contribute beans here GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class); load(loader); } //使用注解加载 if (isComponent(source)) { this.annotatedReader.register(source); return 1; } return 0; }5、下面方法判断启动类中是否包含@Component注解，但是会神奇的发现我们的启动类中并没有该注解，继续更进发现MergedAnnotations类传入了一个参数SearchStrategy.TYPE_HIERARCHY，会查找继承关系中是否包含这个注解，@SpringBootApplication-->@SpringBootConfiguration-->@Configuration-->@Component,当找到@Component注解之后，会把该对象注册到AnnotatedBeanDefinitionReader对象中private boolean isComponent(Class<?> type) { // This has to be a bit of a guess. The only way to be sure that this type is // eligible is to make a bean definition out of it and try to instantiate it. if (MergedAnnotations.from(type, SearchStrategy.TYPE_HIERARCHY).isPresent(Component.class)) { return true; } // Nested anonymous classes are not eligible for registration, nor are groovy // closures return !type.getName().matches(".*\\$_.*closure.*") && !type.isAnonymousClass() && type.getConstructors() != null && type.getConstructors().length != 0; } /** * Register a bean from the given bean class, deriving its metadata from * class-declared annotations. * 从给定的bean class中注册一个bean对象，从注解中找到相关的元数据 */ private <T> void doRegisterBean(Class<T> beanClass, @Nullable String name, @Nullable Class<? extends Annotation>[] qualifiers, @Nullable Supplier<T> supplier, @Nullable BeanDefinitionCustomizer[] customizers) { AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass); if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) { return; } abd.setInstanceSupplier(supplier); ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd); abd.setScope(scopeMetadata.getScopeName()); String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry)); AnnotationConfigUtils.processCommonDefinitionAnnotations(abd); if (qualifiers != null) { for (Class<? extends Annotation> qualifier : qualifiers) { if (Primary.class == qualifier) { abd.setPrimary(true); } else if (Lazy.class == qualifier) { abd.setLazyInit(true); } else { abd.addQualifier(new AutowireCandidateQualifier(qualifier)); } } } if (customizers != null) { for (BeanDefinitionCustomizer customizer : customizers) { customizer.customize(abd); } } BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName); definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry); } /** * Register the given bean definition with the given bean factory. * 注册主类，如果有别名可以设置别名 */ public static void registerBeanDefinition( BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { // Register bean definition under primary name. String beanName = definitionHolder.getBeanName(); registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); // Register aliases for bean name, if any. String[] aliases = definitionHolder.getAliases(); if (aliases != null) { for (String alias : aliases) { registry.registerAlias(beanName, alias); } } } //@SpringBootApplication @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) }) public @interface SpringBootApplication {} //@SpringBootConfiguration @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Configuration public @interface SpringBootConfiguration {} //@Configuration @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Component public @interface Configuration {}当看完上述代码之后，只是完成了启动对象的注入，自动装配还没有开始，下面开始进入到自动装配。6、自动装配入口，从刷新容器开始@Override public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // Prepare this context for refreshing. prepareRefresh(); // Tell the subclass to refresh the internal bean factory. ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. prepareBeanFactory(beanFactory); try { // Allows post-processing of the bean factory in context subclasses. postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context. // 此处是自动装配的入口 invokeBeanFactoryPostProcessors(beanFactory); }7、在invokeBeanFactoryPostProcessors方法中完成bean的实例化和执行/** * Instantiate and invoke all registered BeanFactoryPostProcessor beans, * respecting explicit order if given. * <p>Must be called before singleton instantiation. */ protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { //开始执行beanFactoryPostProcessor对应实现类,需要知道的是beanFactoryPostProcessor是spring的扩展接口，在刷新容器之前，该接口可以用来修改bean元数据信息 PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors()); // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor) if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader())); } }8、查看invokeBeanFactoryPostProcessors的具体执行方法 public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { // Invoke BeanDefinitionRegistryPostProcessors first, if any. Set<String> processedBeans = new HashSet<>(); if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>(); List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>(); //开始遍历三个内部类，如果属于BeanDefinitionRegistryPostProcessor子类，加入到bean注册的集合，否则加入到regularPostProcessors for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; registryProcessor.postProcessBeanDefinitionRegistry(registry); registryProcessors.add(registryProcessor); } else { regularPostProcessors.add(postProcessor); } } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! // Separate between BeanDefinitionRegistryPostProcessors that implement // PriorityOrdered, Ordered, and the rest. List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>(); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. //通过BeanDefinitionRegistryPostProcessor获取到对应的处理类“org.springframework.context.annotation.internalConfigurationAnnotationProcessor”，但是需要注意的是这个类在springboot中搜索不到，这个类的完全限定名在AnnotationConfigEmbeddedWebApplicationContext中，在进行初始化的时候会装配几个类，在创建AnnotatedBeanDefinitionReader对象的时候会将该类注册到bean对象中，此处可以看到internalConfigurationAnnotationProcessor为bean名称，容器中真正的类是ConfigurationClassPostProcessor String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); //首先执行类型为PriorityOrdered的BeanDefinitionRegistryPostProcessor //PriorityOrdered类型表明为优先执行 for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { //获取对应的bean currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); //用来存储已经执行过的BeanDefinitionRegistryPostProcessor processedBeans.add(ppName); } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); //开始执行装配逻辑 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered. //其次执行类型为Ordered的BeanDefinitionRegistryPostProcessor //Ordered表明按顺序执行 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear. //循环中执行类型不为PriorityOrdered，Ordered类型的BeanDefinitionRegistryPostProcessor boolean reiterate = true; while (reiterate) { reiterate = false; postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); reiterate = true; } } sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); } // Now, invoke the postProcessBeanFactory callback of all processors handled so far. //执行父类方法，优先执行注册处理类 invokeBeanFactoryPostProcessors(registryProcessors, beanFactory); //执行有规则处理类 invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); } else { // Invoke factory processors registered with the context instance. invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory); } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, // Ordered, and the rest. List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>(); List<String> orderedPostProcessorNames = new ArrayList<>(); List<String> nonOrderedPostProcessorNames = new ArrayList<>(); for (String ppName : postProcessorNames) { if (processedBeans.contains(ppName)) { // skip - already processed in first phase above } else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class)); } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessorNames.add(ppName); } else { nonOrderedPostProcessorNames.add(ppName); } } // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered. sortPostProcessors(priorityOrderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // Next, invoke the BeanFactoryPostProcessors that implement Ordered. List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size()); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // Finally, invoke all other BeanFactoryPostProcessors. List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size()); for (String postProcessorName : nonOrderedPostProcessorNames) { nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory); // Clear cached merged bean definitions since the post-processors might have // modified the original metadata, e.g. replacing placeholders in values... beanFactory.clearMetadataCache(); }9、开始执行自动配置逻辑（启动类指定的配置，非默认配置），可以通过debug的方式一层层向里进行查找，会发现最终会在ConfigurationClassParser类中，此类是所有配置类的解析类，所有的解析逻辑在parser.parse(candidates)中public void parse(Set<BeanDefinitionHolder> configCandidates) { for (BeanDefinitionHolder holder : configCandidates) { BeanDefinition bd = holder.getBeanDefinition(); try { //是否是注解类 if (bd instanceof AnnotatedBeanDefinition) { parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName()); } else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) { parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName()); } else { parse(bd.getBeanClassName(), holder.getBeanName()); } } catch (BeanDefinitionStoreException ex) { throw ex; } catch (Throwable ex) { throw new BeanDefinitionStoreException( "Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex); } } //执行配置类 this.deferredImportSelectorHandler.process(); } ------------------- protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException { processConfigurationClass(new ConfigurationClass(metadata, beanName)); } ------------------- protected void processConfigurationClass(ConfigurationClass configClass) throws IOException { if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) { return; } ConfigurationClass existingClass = this.configurationClasses.get(configClass); if (existingClass != null) { if (configClass.isImported()) { if (existingClass.isImported()) { existingClass.mergeImportedBy(configClass); } // Otherwise ignore new imported config class; existing non-imported class overrides it. return; } else { // Explicit bean definition found, probably replacing an import. // Let's remove the old one and go with the new one. this.configurationClasses.remove(configClass); this.knownSuperclasses.values().removeIf(configClass::equals); } } // Recursively process the configuration class and its superclass hierarchy. SourceClass sourceClass = asSourceClass(configClass); do { //循环处理bean,如果有父类，则处理父类，直至结束 sourceClass = doProcessConfigurationClass(configClass, sourceClass); } while (sourceClass != null); this.configurationClasses.put(configClass, configClass); }10、继续跟进doProcessConfigurationClass方法，此方式是支持注解配置的核心逻辑/** * Apply processing and build a complete {@link ConfigurationClass} by reading the * annotations, members and methods from the source class. This method can be called * multiple times as relevant sources are discovered. * @param configClass the configuration class being build * @param sourceClass a source class * @return the superclass, or {@code null} if none found or previously processed */ @Nullable protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass) throws IOException { //处理内部类逻辑，由于传来的参数是启动类，并不包含内部类，所以跳过 if (configClass.getMetadata().isAnnotated(Component.class.getName())) { // Recursively process any member (nested) classes first processMemberClasses(configClass, sourceClass); } // Process any @PropertySource annotations //针对属性配置的解析 for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable( sourceClass.getMetadata(), PropertySources.class, org.springframework.context.annotation.PropertySource.class)) { if (this.environment instanceof ConfigurableEnvironment) { processPropertySource(propertySource); } else { logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() + "]. Reason: Environment must implement ConfigurableEnvironment"); } } // Process any @ComponentScan annotations // 这里是根据启动类@ComponentScan注解来扫描项目中的bean Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable( sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class); if (!componentScans.isEmpty() && !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) { for (AnnotationAttributes componentScan : componentScans) { // The config class is annotated with @ComponentScan -> perform the scan immediately //遍历项目中的bean，如果是注解定义的bean，则进一步解析 Set<BeanDefinitionHolder> scannedBeanDefinitions = this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName()); // Check the set of scanned definitions for any further config classes and parse recursively if needed for (BeanDefinitionHolder holder : scannedBeanDefinitions) { BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition(); if (bdCand == null) { bdCand = holder.getBeanDefinition(); } if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) { //递归解析，所有的bean,如果有注解，会进一步解析注解中包含的bean parse(bdCand.getBeanClassName(), holder.getBeanName()); } } } } // Process any @Import annotations //递归解析，获取导入的配置类，很多情况下，导入的配置类中会同样包含导入类注解 processImports(configClass, sourceClass, getImports(sourceClass), true); // Process any @ImportResource annotations //解析@ImportResource配置类 AnnotationAttributes importResource = AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class); if (importResource != null) { String[] resources = importResource.getStringArray("locations"); Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader"); for (String resource : resources) { String resolvedResource = this.environment.resolveRequiredPlaceholders(resource); configClass.addImportedResource(resolvedResource, readerClass); } } // Process individual @Bean methods //处理@Bean注解修饰的类 Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass); for (MethodMetadata methodMetadata : beanMethods) { configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass)); } // Process default methods on interfaces // 处理接口中的默认方法 processInterfaces(configClass, sourceClass); // Process superclass, if any //如果该类有父类，则继续返回，上层方法判断不为空，则继续递归执行 if (sourceClass.getMetadata().hasSuperClass()) { String superclass = sourceClass.getMetadata().getSuperClassName(); if (superclass != null && !superclass.startsWith("java") && !this.knownSuperclasses.containsKey(superclass)) { this.knownSuperclasses.put(superclass, configClass); // Superclass found, return its annotation metadata and recurse return sourceClass.getSuperClass(); } } // No superclass -> processing is complete return null; } 11、查看获取配置类的逻辑processImports(configClass, sourceClass, getImports(sourceClass), true); /** * Returns {@code @Import} class, considering all meta-annotations. */ private Set<SourceClass> getImports(SourceClass sourceClass) throws IOException { Set<SourceClass> imports = new LinkedHashSet<>(); Set<SourceClass> visited = new LinkedHashSet<>(); collectImports(sourceClass, imports, visited); return imports; } ------------------ /** * Recursively collect all declared {@code @Import} values. Unlike most * meta-annotations it is valid to have several {@code @Import}s declared with * different values; the usual process of returning values from the first * meta-annotation on a class is not sufficient. * <p>For example, it is common for a {@code @Configuration} class to declare direct * {@code @Import}s in addition to meta-imports originating from an {@code @Enable} * annotation. * 看到所有的bean都以导入的方式被加载进去 */ private void collectImports(SourceClass sourceClass, Set<SourceClass> imports, Set<SourceClass> visited) throws IOException { if (visited.add(sourceClass)) { for (SourceClass annotation : sourceClass.getAnnotations()) { String annName = annotation.getMetadata().getClassName(); if (!annName.equals(Import.class.getName())) { collectImports(annotation, imports, visited); } } imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), "value")); } }12、继续回到ConfigurationClassParser中的parse方法中的最后一行,继续跟进该方法：this.deferredImportSelectorHandler.process() ------------- public void process() { List<DeferredImportSelectorHolder> deferredImports = this.deferredImportSelectors; this.deferredImportSelectors = null; try { if (deferredImports != null) { DeferredImportSelectorGroupingHandler handler = new DeferredImportSelectorGroupingHandler(); deferredImports.sort(DEFERRED_IMPORT_COMPARATOR); deferredImports.forEach(handler::register); handler.processGroupImports(); } } finally { this.deferredImportSelectors = new ArrayList<>(); } } --------------- public void processGroupImports() { for (DeferredImportSelectorGrouping grouping : this.groupings.values()) { grouping.getImports().forEach(entry -> { ConfigurationClass configurationClass = this.configurationClasses.get( entry.getMetadata()); try { processImports(configurationClass, asSourceClass(configurationClass), asSourceClasses(entry.getImportClassName()), false); } catch (BeanDefinitionStoreException ex) { throw ex; } catch (Throwable ex) { throw new BeanDefinitionStoreException( "Failed to process import candidates for configuration class [" + configurationClass.getMetadata().getClassName() + "]", ex); } }); } } ------------ /** * Return the imports defined by the group. * @return each import with its associated configuration class */ public Iterable<Group.Entry> getImports() { for (DeferredImportSelectorHolder deferredImport : this.deferredImports) { this.group.process(deferredImport.getConfigurationClass().getMetadata(), deferredImport.getImportSelector()); } return this.group.selectImports(); } } ------------ public DeferredImportSelector getImportSelector() { return this.importSelector; } ------------ @Override public void process(AnnotationMetadata annotationMetadata, DeferredImportSelector deferredImportSelector) { Assert.state(deferredImportSelector instanceof AutoConfigurationImportSelector, () -> String.format("Only %s implementations are supported, got %s", AutoConfigurationImportSelector.class.getSimpleName(), deferredImportSelector.getClass().getName())); AutoConfigurationEntry autoConfigurationEntry = ((AutoConfigurationImportSelector) deferredImportSelector) .getAutoConfigurationEntry(getAutoConfigurationMetadata(), annotationMetadata); this.autoConfigurationEntries.add(autoConfigurationEntry); for (String importClassName : autoConfigurationEntry.getConfigurations()) { this.entries.putIfAbsent(importClassName, annotationMetadata); } }