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SpringBoot内置Tomcat启动原理源码分析

SpringBoot

1、获取SpringBoot内置Tomcat自动配置类：
在SpringBoot项目中引入spring-boot-starter-web依赖，就默认使用Tomcat容器，该依赖中引入
spring-boot-starter-tomcat、spring-webmvc，就引入了tomtcat核心依赖和springMvc相关jar包，这样就间接地引入了tomcat 。

SpringBoot内置Tomcat启动原理源码分析

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在执行SpringBoot项目启动类的main()方法，启动SpringBoot项目的过程中会加载各个jar包下META-INF/spring.factories的文件，在该文件中包含着自动配置的子路径，在refresh()方法中的
invokeBeanFactoryPostProcessors()中首先会对启动类上的 @SpringBootApplication 注解进行解析，最终调用 AutoConfigurationImportSelector类中的 getAutoConfigurationEntry() 加载 META-INF/spring.factories 文件中的自动配置类，得到自动配置类的全路径,其中 org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration 为tomcat自动配置类 。
具体加载流程见: springBoot-启动原理 - sun丶牧羊人 - 博客园
protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {if (!isEnabled(annotationMetadata)) {return EMPTY_ENTRY;}AnnotationAttributes attributes = getAttributes(annotationMetadata);// 1、得到META-INF/spring.factories文件中配置的所有自动配置类List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);// 移除重复的配置类configurations = removeDuplicates(configurations);// 获取需要排除的自动配置类，eg:注解属性中的exculde的配置类Set<String> exclusions = getExclusions(annotationMetadata, attributes);// 检查需要被排除的配置类，因为有些不是自动配置类，需要抛异常checkExcludedClasses(configurations, exclusions);// 移除需要排除的配置类configurations.removeAll(exclusions);// 根据 META-INF/spring-autoconfigure-metadata.properties 中配置的规则过虑掉一部分配置类(根据@ConditionalOnXXX注解进行过滤)configurations = getConfigurationClassFilter().filter(configurations);// 获取符合条件的配置类后，触发 AutoConfigurationImportEvent 事件fireAutoConfigurationImportEvents(configurations, exclusions);// 将符合条件和需要排除的配置类封装进 AutoConfigurationEntry 对象中返回return new AutoConfigurationEntry(configurations, exclusions);}
SpringBoot内置Tomcat启动原理源码分析

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2、
ServletWebServerFactoryAutoConfiguration - tomcat自动配置类分析
SpringBoot内置Tomcat启动原理源码分析

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3、创建tomcat工厂
【SpringBoot内置Tomcat启动原理源码分析】@Configuration(proxyBeanMethods = false)@ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })@ConditionalOnMissingBean(value = https://www.isolves.com/it/cxkf/jiagou/2022-02-22/ServletWebServerFactory.class, search = SearchStrategy.CURRENT)static class EmbeddedTomcat {@BeanTomcatServletWebServerFactory tomcatServletWebServerFactory(ObjectProvider connectorCustomizers,ObjectProvider contextCustomizers,ObjectProvider> protocolHandlerCustomizers) {// 创建生产tomcat的工厂TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();factory.getTomcatConnectorCustomizers().addAll(connectorCustomizers.orderedStream().collect(Collectors.toList()));factory.getTomcatContextCustomizers().addAll(contextCustomizers.orderedStream().collect(Collectors.toList()));factory.getTomcatProtocolHandlerCustomizers().addAll(protocolHandlerCustomizers.orderedStream().collect(Collectors.toList()));return factory;}}　4、创建tomcat容器
在SpringBoot启动过程中会调用
AbstractApplicationContext.refresh() 方法，在该方法会调用onRefresh()方法，这个方法是个模板方法，最终会交给子类实现，在使用内置tomcat的SpringBoot项目中，最终会调用 ServletWebServerApplicationContext 实现(AbstractApplicationContext是GenericWebApplicationContext，ServletWebServerApplicationContext 是GenericWebApplicationContext)，最终调用ServletWebServerApplicationContext 的createWebServer()方法创建 webServer 。
@Configuration(proxyBeanMethods = false)@ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })@ConditionalOnMissingBean(value = https://www.isolves.com/it/cxkf/jiagou/2022-02-22/ServletWebServerFactory.class, search = SearchStrategy.CURRENT)protected void onRefresh() {// 调用 GenericWebApplicationContext类的 onRefresh() 方法，super.onRefresh();try {// 获取嵌入式的Servlet容器工厂(TomcatServletWebServerFactory)，并通过工厂来获取Servlet容器createWebServer();}catch (Throwable ex) {throw new ApplicationContextException("Unable to start web server", ex);}}private void createWebServer() {WebServer webServer = this.webServer;ServletContext servletContext = getServletContext();if (webServer == null && servletContext == null) {StartupStep createWebServer = this.getApplicationStartup().start("spring.boot.webserver.create");// 获取 Servlet容器工厂ServletWebServerFactory factory = getWebServerFactory();createWebServer.tag("factory", factory.getClass().toString());// 通过Servlet容器工厂加载tomcat并启动tomcatthis.webServer = factory.getWebServer(getSelfInitializer());createWebServer.end();getBeanFactory().registerSingleton("webServerGracefulShutdown",new WebServerGracefulShutdownLifecycle(this.webServer));getBeanFactory().registerSingleton("webServerStartStop",new WebServerStartStopLifecycle(this, this.webServer));}else if (servletContext != null) {try {getSelfInitializer().onStartup(servletContext);}catch (ServletException ex) {throw new ApplicationContextException("Cannot initialize servlet context", ex);}}initPropertySources();}在 TomcatServletWebServerFactory 类中@Overridepublic WebServer getWebServer(ServletContextInitializer... initializers) {if (this.disableMBeanRegistry) {Registry.disableRegistry();}// 实例化tomcatTomcat tomcat = new Tomcat();File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");// 设置tomcat临时工作目录tomcat.setBaseDir(baseDir.getAbsolutePath());// 默认使用 org.Apache.coyote.http11.Http11NioProtocol 实例化ConnectorConnector connector = new Connector(this.protocol);connector.setThrowOnFailure(true);// 给service添加Connectortomcat.getService().addConnector(connector);customizeConnector(connector);tomcat.setConnector(connector);// 关闭热部署tomcat.getHost().setAutoDeploy(false);// 配置 EngineconfigureEngine(tomcat.getEngine());for (Connector additionalConnector : this.additionalTomcatConnectors) {tomcat.getService().addConnector(additionalConnector);}prepareContext(tomcat.getHost(), initializers);// 实例化 TomcatWebServer，将 DispatcherServlet 以及一些Filter添加到Tomcat中return getTomcatWebServer(tomcat);}protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {return new TomcatWebServer(tomcat, getPort() >= 0, getShutdown());}//TomcatWebServer类的构造方法public TomcatWebServer(Tomcat tomcat, boolean autoStart, Shutdown shutdown) {Assert.notNull(tomcat, "Tomcat Server must not be null");this.tomcat = tomcat;this.autoStart = autoStart;this.gracefulShutdown = (shutdown == Shutdown.GRACEFUL) ? new GracefulShutdown(tomcat) : null;initialize();}private void initialize() throws WebServerException {logger.info("Tomcat initialized with port(s): " + getPortsDescription(false));synchronized (this.monitor) {try {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.removeServiceConnectors();}});// Start the server to trigger initialization listeners//利用LifecycleBase对这一套容器（engine，host，context及wrapper）进行启动并发布configure_start、// before_init、after_start的lifecycleEvent等事件给相应的监听器// 本方法并没有启动tomcatthis.tomcat.start();// We can re-throw failure exception directly in the main threadrethrowDeferredStartupExceptions();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 shutdownstartDaemonAwaitThread();}catch (Exception ex) {stopSilently();destroySilently();throw new WebServerException("Unable to start embedded Tomcat", ex);}}}// Tomcat类public void start() throws LifecycleException {getServer();server.start();}// LifecycleBasepublic final synchronized void start() throws LifecycleException {if (LifecycleState.STARTING_PREP.equals(state) || LifecycleState.STARTING.equals(state) ||LifecycleState.STARTED.equals(state)) {if (log.isDebugEnabled()) {Exception e = new LifecycleException();log.debug(sm.getString("lifecycleBase.alreadyStarted", toString()), e);} else if (log.isInfoEnabled()) {log.info(sm.getString("lifecycleBase.alreadyStarted", toString()));}return;}if (state.equals(LifecycleState.NEW)) {init();} else if (state.equals(LifecycleState.FAILED)) {stop();} else if (!state.equals(LifecycleState.INITIALIZED) &&!state.equals(LifecycleState.STOPPED)) {invalidTransition(Lifecycle.BEFORE_START_EVENT);}try {setStateInternal(LifecycleState.STARTING_PREP, null, false);startInternal();if (state.equals(LifecycleState.FAILED)) {// This is a 'controlled' failure. The component put itself into the// FAILED state so call stop() to complete the clean-up.stop();} else if (!state.equals(LifecycleState.STARTING)) {// Shouldn't be necessary but acts as a check that sub-classes are// doing what they are supposed to.invalidTransition(Lifecycle.AFTER_START_EVENT);} else {setStateInternal(LifecycleState.STARTED, null, false);}} catch (Throwable t) {// This is an 'uncontrolled' failure so put the component into the// FAILED state and throw an exception.handleSubClassException(t, "lifecycleBase.startFail", toString());}}


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