Docker安装Jenkins自动部署SpringBoot项目 Docker安装Jenkins自动部署SpringBoot项目根据之前文章《使用Docker安装好Jenkins》为前提搭建好Jenkins，不明白请看https://www.yanxizhu.com/index.php/archives/138/。环境说明：jenkins为docker部署，Docker+Jenkins+Gitee+JDK11+Maven3.8.5。以后每次改动代码，push提交到giee码云后会自动部署，不用手动点击部署。一、全局工具配置【首页】-【系统管理】-【全局工具配置】我之前启动jenkins容器映射参数如下，根据自己映射路径自行修改。docker run -p 10240:8080 -p 10241:50000 --name jenkins \ -u root \ -v /mydata/jenkins_home:/var/jenkins_home \ -v /mydata/maven/apache-maven-3.8.5:/maven/apache-maven-3.8.5 \ -v /mydata/jdk/jdk-11.0.10/:/jdk/jdk-11.0.10 \ -v /mydata/maven/repo:/mydata/maven/repo \ -v /usr/bin/docker:/usr/bin/docker \ -v /var/run/docker.sock:/var/run/docker.sock \ -d jenkins/jenkins:lts上面很重要，注意。jdk配置jdk11路径/jdk/jdk-11.0.10maven配置maven3.8.5路径/maven/apache-maven-3.8.5git配置Default路径/usr/bin/gitdocker配置docker路径/usr/bin注意点：1、jenkins容器里面自带git，可通过命令查看路径。2、注意自己jdk、mavn、docker安装路径。查看jenkins自带git路径命令：which git二、插件安装【首页】-【系统管理】-【插件管理】插件1：Publish Over SSH插件2：Gitee Plugin如果插件安装慢，可以修改源，请参考修改方案，https://www.yanxizhu.com/index.php/archives/138/注意：如果在【全局工具配置】没有对应的选项，就是缺少相应插件。三、系统配置1、SSH remote hosts配置新增加配置ssh登陆凭证，此步骤的主要作用是jenkins 打包镜像后，能够远程去登陆和执行脚本文件。Hostname：xxx.xxx.xxx.x..(需要登陆的服务器ip)Port：22（ssh登陆端口）Credentials：登陆账号和密码（此处点击[添加]按钮增加一个）如果是本机可以不用配置2、Gitee 配置链接名：giteeGitee 域名 URL：https://gitee.com添加凭证Gitee API V5 的私人令牌（获取地址 https://gitee.com/profile/personal_access_tokens）通过上面连接创建一个令牌，然后添加到这里。四、准备项目1、本地新建一个SpringBoot项目，新建HellocerConller控制层package com.yanxizhu.jenkins.demo.controller; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; /** * @description: Jenkins自动部署测试 * @author: <a href="mailto:batis@foxmail.com">清风</a> * @date: 2022/5/8 17:30 * @version: 1.0 */ @RestController public class HelloController { @GetMapping("/hello") public String hello(){ return "Hello World!"; } }本地启动项目确保通过127.0.0.1:8080/hello能够访问。2、编写Dockerfile# 指定是基于哪个基础镜像 FROM openjdk:11 # 作者信息 MAINTAINER batis # 挂载点声明 VOLUME /tmp # 将本地的一个文件或目录，拷贝到容器的文件或目录里 ADD /target/jenkins-demo-0.0.1-SNAPSHOT.jar springboot.jar #shell脚本 RUN bash -c 'touch /springboot.jar' # 将容器的8000端口暴露，给外部访问。 EXPOSE 8000 # 当容器运行起来时执行使用运行jar的指令 ENTRYPOINT ["java", "-jar", "springboot.jar"]注意：修改jdk版本、打包后名称、端口信息五、代码上传登录码云新建仓库，名字随意将代码关联并提交到码云。新建仓库、代码push自行google。六、WebHooks 管理配置1、打开仓库 -> 管理 -> 右侧的webhooksURL：填入服务器公网IP地址WebHook密码通过以下生成。七、部署SpringBoot项目1、新建部署任务任务名字随意、构建一个自由风格的软件项目。2、General描述随意填写，丢弃旧的构建策略,保持构建的天数1，保持构建的最大个数3，根据自己需要自行修改。3、源码管理选择gitRepository URL为自己gitee码云仓库地址。Credentials点击“添加”，Credentials凭证，选择通过用户名密码添加，id、备注可以为空。4、构建触发器其它默认：找到Gitee WebHook 密码，点击“生成按钮”生成，然后将该密码填入上面 “六、WebHooks 管理配置”中。轮询 SCM策略：* * * * *注意：*中间有空格，当您输入 "* * * * *" 时，意思为"每分钟"？也许您希望 "H * * * *" 每小时轮询。5、构建选择执行shell脚本#!/bin/bash -lex docker rm -f app_docker sleep 1 docker rmi -f app_docker:1.0 sleep 1 mvn clean install -Dmaven.test.skip=true sleep 1 docker build -t app_docker:1.0 -f ./src/main/Dockerfile . sleep 1 docker run -d -p 8000:8000 --name app_docker app_docker:1.0 注意自己端口名称。6、访问测试通过自己xxx.xxx.xx.xx:8000/hello即可自己写的helloword了。以后每次改动代码，push提交到giee码云后会自动部署，不用手动点击部署。7、问题记录及解决方案比如：1、查不到mvn、docker、jdk命令，可能是jenkins容器中环境配置问题，可以参考《Jenkins容器docker部署springboot项目-问题记录》2、如果开启了防火墙注意开发相应端口或关闭防火墙3、部署遇到问题，查看部署日志，以及google、baidu相关参考：Docker开启Remote API访问docker启动Jenkins报错Docker安装JenkinsNginx配置Jenkins二级域名，以及443 SSL证书访问Jenkins容器docker部署springboot项目-问题记录

Jenkins容器docker部署springboot项目-问题记录 Jenkins容器docker部署springboot项目-问题记录一、docker容器内不能使用vim解决方案：以root进入容器内docker exec -it -user root jenkins /bin/bash更新软件包apt-get update升级过程可能非常慢，因为是从海外站点拉取镜像，所以我们可以配置一个国内的镜像源，加速镜像拉取更新。备份原文件mv /etc/apt/sources.list /etc/apt/sources.list.bak查看容器中Debian版本cat /etc/issue修改配置sources.list文件根据自己版本修改成对应内容，修改内容参考阿里镜像https://developer.aliyun.com/mirror/debian我容器Debian为11.x版本，修改内容为：cat >/etc/apt/sources.list <<EOF deb http://mirrors.aliyun.com/debian/ bullseye main non-free contrib deb-src http://mirrors.aliyun.com/debian/ bullseye main non-free contrib deb http://mirrors.aliyun.com/debian-security/ bullseye-security main deb-src http://mirrors.aliyun.com/debian-security/ bullseye-security main deb http://mirrors.aliyun.com/debian/ bullseye-updates main non-free contrib deb-src http://mirrors.aliyun.com/debian/ bullseye-updates main non-free contrib deb http://mirrors.aliyun.com/debian/ bullseye-backports main non-free contrib deb-src http://mirrors.aliyun.com/debian/ bullseye-backports main non-free contrib EOF重新执行apt-get update安装vimapt-get install -y vim安装rpmapt-get install rpm -y二、docker容器内vim不能粘贴内容vim右键进入visual模式无法粘贴解决方案vim /usr/share/vim/vim80/defaults.vim修改内容：第70行，在mouse=a的=前面加个-，修改后如下：if has('mouse') set mouse-=a endif三、docker容器内环境配置修改环境变量配置vi /etc/profile新增jdk、mavn环境变量配置# java环境变量 export JAVA_HOME=/jdk/jdk-11.0.10 export JRE_HOME=$JAVA_HOME/jre export PATH=$JAVA_HOME/bin:$PATH export CLASSPATH=./:JAVA_HOME/lib:$JRE_HOME/lib # maven环境变量 export M2_HOME=/maven/apache-maven-3.8.5 export PATH=$PATH:$JAVA_HOME/bin:$M2_HOME/bin重新加载环境变量source /etc/profile检验是否配置成功java -version mvn -v

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。