ServletWebServerApplicationContext創建Web容器Tomcat示例

ServletWebServerApplicationContext實現了父類AbstractApplicationContext的onRefresh模板方法，在這里進行了拓展創建了Web容器。

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@Override protected void onRefresh() {    super.onRefresh();    try {       createWebServer();    }    catch (Throwable ex) {       throw new ApplicationContextException("Unable to start web server", ex);    } }

創建Web服務

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private void createWebServer() {    WebServer webServer = this.webServer;    ServletContext servletContext = getServletContext();    if (webServer == null && servletContext == null) {       //一、獲取Web服務器工廠       ServletWebServerFactory factory = getWebServerFactory();       //二、獲取Web服務       this.webServer = factory.getWebServer(getSelfInitializer());       //三、注冊Bean生命周期（在容器啟動和銷毀時調用）       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);       }    }    //四、初始化上下文環境    initPropertySources(); }

一、獲取Web服務器工廠

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protected ServletWebServerFactory getWebServerFactory() {    // Use bean names so that we don't consider the hierarchy    //獲取Web服務器工廠名稱    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));    }    //從容器中獲取Web服務器工廠實例    return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class); }

這里的Web服務器工廠是通過ServletWebServerFactoryAutoConfiguration自動配置類導入進來的。

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@Configuration(proxyBeanMethods = false) @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE) @ConditionalOnClass(ServletRequest.class) //Web啟動環境 @ConditionalOnWebApplication(type = Type.SERVLET) @EnableConfigurationProperties(ServerProperties.class) //2.1導入Web工廠 @Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,       ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,       ServletWebServerFactoryConfiguration.EmbeddedJetty.class,       ServletWebServerFactoryConfiguration.EmbeddedUndertow.class }) public class ServletWebServerFactoryAutoConfiguration {    //導入Web服務器工廠自定義程序    @Bean    public ServletWebServerFactoryCustomizer servletWebServerFactoryCustomizer(ServerProperties serverProperties) {       return new ServletWebServerFactoryCustomizer(serverProperties);    }    //如果是Tomcat則導入Tomcat自定義程序    @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);          }       }    } }

1.1 選擇導入Web工廠

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@Configuration class ServletWebServerFactoryConfiguration {     ServletWebServerFactoryConfiguration() {     }     //1.如果容器中有Servlet，Undertow，SslClientAuthMode就會創建Undertow工廠     @Configuration     @ConditionalOnClass({Servlet.class, Undertow.class, SslClientAuthMode.class})     @ConditionalOnMissingBean(         value = {ServletWebServerFactory.class},         search = SearchStrategy.CURRENT     )     public static class EmbeddedUndertow {         public EmbeddedUndertow() {         }         @Bean         public UndertowServletWebServerFactory undertowServletWebServerFactory() {             return new UndertowServletWebServerFactory();         }     }     //2.如果容器中有Servlet，Server，Loader就會創建Jetty工廠     @Configuration     @ConditionalOnClass({Servlet.class, Server.class, Loader.class, WebAppContext.class})     @ConditionalOnMissingBean(         value = {ServletWebServerFactory.class},         search = SearchStrategy.CURRENT     )     public static class EmbeddedJetty {         public EmbeddedJetty() {         }         @Bean         public JettyServletWebServerFactory JettyServletWebServerFactory() {             return new JettyServletWebServerFactory();         }     }     //3.如果容器中有Servlet，Tomcat，UpgradeProtocol就會創建Tomcat工廠     @Configuration     @ConditionalOnClass({Servlet.class, Tomcat.class, UpgradeProtocol.class})     @ConditionalOnMissingBean(         value = {ServletWebServerFactory.class},         search = SearchStrategy.CURRENT     )     public static class EmbeddedTomcat {         public EmbeddedTomcat() {         }         @Bean         public TomcatServletWebServerFactory tomcatServletWebServerFactory() {             return new TomcatServletWebServerFactory();         }     } }

二、getWebServer：獲取Web服務

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public static final String DEFAULT_PROTOCOL = "org.apache.coyote.http11.Http11NioProtocol"; private String protocol = DEFAULT_PROTOCOL; public WebServer getWebServer(ServletContextInitializer... initializers) {     Tomcat tomcat = new Tomcat();     // 給嵌入式Tomcat創建一個臨時文件夾，用于存放Tomcat運行中需要的文件     File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");     tomcat.setBaseDir(baseDir.getAbsolutePath());     // Tomcat核心概念：Connector，默認放入的protocol為NIO模式     Connector connector = new Connector(this.protocol);     // 給Service添加Connector     tomcat.getService().addConnector(connector);     // 執行定制器，修改即將設置到Tomcat中的Connector     customizeConnector(connector);     tomcat.setConnector(connector);     // 關閉熱部署（嵌入式Tomcat不存在修改web.xml、war包等情況）     tomcat.getHost().setAutoDeploy(false);     // 設置backgroundProcessorDelay機制     configureEngine(tomcat.getEngine());     for (Connector additionalConnector : this.additionalTomcatConnectors) {         tomcat.getService().addConnector(additionalConnector);     }     // 2.1 創建TomcatEmbeddedContext     prepareContext(tomcat.getHost(), initializers);     // 2.2. 創建TomcatWebServer     return getTomcatWebServer(tomcat); }

2.1 創建TomcatEmbeddedContext

（注釋均已在源碼中標注好，小伙伴們對哪一步感興趣可以借助IDE自己動手Debug體會一下實現）

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protected void prepareContext(Host host, ServletContextInitializer[] initializers) {     File documentRoot = getValidDocumentRoot();     // 創建TomcatEmbeddedContext     TomcatEmbeddedContext context = new TomcatEmbeddedContext();     if (documentRoot != null) {         context.setResources(new LoaderHidingResourceRoot(context));     }     context.setName(getContextPath());     context.setDisplayName(getDisplayName());     // 設置contextPath，很熟悉了     context.setPath(getContextPath());     // 給嵌入式Tomcat創建docbase的臨時文件夾     File docBase = (documentRoot != null) ? documentRoot : createTempDir("tomcat-docbase");     context.setDocBase(docBase.getAbsolutePath());     // 注冊監聽器     context.addLifecycleListener(new FixContextListener());     context.setParentClassLoader((this.resourceLoader != null) ? this.resourceLoader.getClassLoader()             : ClassUtils.getDefaultClassLoader());     // 設置默認編碼映射     resetDefaultLocaleMapping(context);     addLocaleMappings(context);     context.setUseRelativeRedirects(false);     try {         context.setCreateUploadTargets(true);     }     catch (NoSuchMethodError ex) {         // Tomcat is < 8.5.39. Continue.     }     configureTldSkipPatterns(context);     // 自定義的類加載器，可以加載web應用的jar包     WebappLoader loader = new WebappLoader(context.getParentClassLoader());     loader.setLoaderClass(TomcatEmbeddedWebappClassLoader.class.getName());     // 指定類加載器遵循雙親委派機制     loader.setDelegate(true);     context.setLoader(loader);     // 注冊默認的Servlet     if (isRegisterDefaultServlet()) {         addDefaultServlet(context);     }     // 如果需要jsp支持，注冊jsp的Servlet和Initializer     if (shouldRegisterJspServlet()) {         addJspServlet(context);         addJasperInitializer(context);     }     // 注冊監聽器     context.addLifecycleListener(new StaticResourceConfigurer(context));     ServletContextInitializer[] initializersToUse = mergeInitializers(initializers);     host.addChild(context);     configureContext(context, initializersToUse);     postProcessContext(context); }

2.2. 創建TomcatWebServer

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protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {    return new TomcatWebServer(tomcat, getPort() >= 0, getShutdown()); }

進入TomcatWebServer構造方法中：

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public TomcatWebServer(Tomcat tomcat, boolean autoStart) {     Assert.notNull(tomcat, "Tomcat Server must not be null");     this.tomcat = tomcat;     this.autoStart = autoStart;     //初始化服務     initialize(); }

初始化TomcatWebServer

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private void initialize() throws WebServerException {    logger.info("Tomcat initialized with port(s): " + getPortsDescription(false));    synchronized (this.monitor) {       try {          //設置Engine的id          addInstanceIdToEngineName();          //獲取Context（TomcatEmbeddedContext  2.1中創建出來的）          Context context = findContext();          //添加監聽器 TomcatEmbeddedContext          //在服務啟動時如果有連接進來先刪除連接，以便在啟動服務時不會發生協議綁定。          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.                //刪除ServiceConnectors，以便在啟動服務時不會發生協議綁定。                removeServiceConnectors();             }          });          // Start the server to trigger initialization listeners          //2.2.1 啟動Tomcat          this.tomcat.start();          // We can re-throw failure exception directly in the main thread          //Tomcat啟動有異常需要在主線程中拋出          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          //開啟阻塞非守護線程停止web容器          startDaemonAwaitThread();       }       catch (Exception ex) {          stopSilently();          destroySilently();          throw new WebServerException("Unable to start embedded Tomcat", ex);       }    } }

2.2.1 啟動Tomcat

創建和初始化Server和Service

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public void start() throws LifecycleException {     //創建服務（Server和Service）     getServer();     server.start(); }

啟動服務

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public final synchronized void start() throws LifecycleException {     //如果是正在啟動或啟動狀態     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;     }     //如果是新建狀態     if (state.equals(LifecycleState.NEW)) {         //2.2.1.1 初始化服務         init();     //如果是失敗狀態        } else if (state.equals(LifecycleState.FAILED)) {         //停止服務         stop();     //如果不是初始化也不是停止狀態     } else if (!state.equals(LifecycleState.INITIALIZED) &&             !state.equals(LifecycleState.STOPPED)) {         //修改狀態         invalidTransition(Lifecycle.BEFORE_START_EVENT);     }     try {         //修改狀態為準備啟動         setStateInternal(LifecycleState.STARTING_PREP, null, false);         //2.2.1.2 啟動Internal         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());     } }

2.2.1.1 初始化Server

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public final synchronized void init() throws LifecycleException {     if (!state.equals(LifecycleState.NEW)) {         invalidTransition(Lifecycle.BEFORE_INIT_EVENT);     }     try {         //設置狀態為初始化         setStateInternal(LifecycleState.INITIALIZING, null, false);         //初始化         initInternal();         //設置狀態為初始化完成         setStateInternal(LifecycleState.INITIALIZED, null, false);     } catch (Throwable t) {         handleSubClassException(t, "lifecycleBase.initFail", toString());     } }

初始化 Server

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protected void initInternal() throws LifecycleException {     //調用父類初始化（設置名稱：Tomcat，類型：Server）     super.initInternal();     // Initialize utility executor     reconfigureUtilityExecutor(getUtilityThreadsInternal(utilityThreads));     //注冊線程池     register(utilityExecutor, "type=UtilityExecutor");     // Register global String cache     // Note although the cache is global, if there are multiple Servers     // present in the JVM (may happen when embedding) then the same cache     // will be registered under multiple names     //注冊字符串緩存     onameStringCache = register(new StringCache(), "type=StringCache");     // Register the MBeanFactory     MBeanFactory factory = new MBeanFactory();     factory.setContainer(this);     //注冊Bean工廠     onameMBeanFactory = register(factory, "type=MBeanFactory");     // Register the naming resources     //注冊命名資源     globalNamingResources.init();     // Populate the extension validator with JARs from common and shared     // class loaders     if (getCatalina() != null) {         ClassLoader cl = getCatalina().getParentClassLoader();         // Walk the class loader hierarchy. Stop at the system class loader.         // This will add the shared (if present) and common class loaders         while (cl != null && cl != ClassLoader.getSystemClassLoader()) {             if (cl instanceof URLClassLoader) {                 URL[] urls = ((URLClassLoader) cl).getURLs();                 for (URL url : urls) {                     if (url.getProtocol().equals("file")) {                         try {                             File f = new File (url.toURI());                             if (f.isFile() &&                                     f.getName().endsWith(".jar")) {                                 ExtensionValidator.addSystemResource(f);                             }                         } catch (URISyntaxException e) {                             // Ignore                         } catch (IOException e) {                             // Ignore                         }                     }                 }             }             cl = cl.getParent();         }     }     // Initialize our defined Services     //2.2.1.1.1 初始化service（2.2.1最開始時創建）     for (Service service : services) {         service.init();     } }

初始化Service

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public final synchronized void init() throws LifecycleException {     if (!state.equals(LifecycleState.NEW)) {         invalidTransition(Lifecycle.BEFORE_INIT_EVENT);     }     try {         //設置狀態為初始化         setStateInternal(LifecycleState.INITIALIZING, null, false);         //初始化         initInternal();         //設置狀態為初始化完成         setStateInternal(LifecycleState.INITIALIZED, null, false);     } catch (Throwable t) {         handleSubClassException(t, "lifecycleBase.initFail", toString());     } }

初始化Service

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protected void initInternal() throws LifecycleException {     //調用父類初始化（設置名稱：Tomcat，類型：Server）     super.initInternal();     //2.2.1.1.1.1 初始化engine     if (engine != null) {         engine.init();     }     // Initialize any Executors     //2.2.1.1.1.2 初始化executor     for (Executor executor : findExecutors()) {         if (executor instanceof JmxEnabled) {             ((JmxEnabled) executor).setDomain(getDomain());         }         executor.init();     }     // Initialize mapper listener     //2.2.1.1.1.3 初始化mapperListener     mapperListener.init();     // Initialize our defined Connectors     //2.2.1.1.1.4 初始化connector     synchronized (connectorsLock) {         for (Connector connector : connectors) {             connector.init();         }     } }

初始化engine

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protected void initInternal() throws LifecycleException {     // Ensure that a Realm is present before any attempt is made to start     // one. This will create the default NullRealm if necessary.     // 在嘗試啟動一個Realm之前，請確保存在一個Realm。如有必要，這將創建默認的NullRealm     getRealm();     super.initInternal(); } public Realm getRealm() {     Realm configured = super.getRealm();     // If no set realm has been called - default to NullRealm     // This can be overridden at engine, context and host level     if (configured == null) {         configured = new NullRealm();         this.setRealm(configured);     }     return configured; }

初始化executor

它還是調的父類 LifecycleMBeanBase 的方法

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protected void initInternal() throws LifecycleException {     super.initInternal(); }

初始化mapperListener

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protected void initInternal() throws LifecycleException {     // If oname is not null then registration has already happened via preRegister().     // 如果oname不為null，則已經通過preRegister()進行了注冊     if (oname == null) {         mserver = Registry.getRegistry(null, null).getMBeanServer();         oname = register(this, getObjectNameKeyProperties());     } }

初始化connector

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protected void initInternal() throws LifecycleException {     super.initInternal();     if (protocolHandler == null) {         throw new LifecycleException(                 sm.getString("coyoteConnector.protocolHandlerInstantiationFailed"));     }     // Initialize adapter     adapter = new CoyoteAdapter(this);     protocolHandler.setAdapter(adapter);     if (service != null) {         protocolHandler.setUtilityExecutor(service.getServer().getUtilityExecutor());     }     // Make sure parseBodyMethodsSet has a default     if (null == parseBodyMethodsSet) {         setParseBodyMethods(getParseBodyMethods());     }     if (protocolHandler.isAprRequired() && !AprStatus.isInstanceCreated()) {         throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprListener",                 getProtocolHandlerClassName()));     }     if (protocolHandler.isAprRequired() && !AprStatus.isAprAvailable()) {         throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprLibrary",                 getProtocolHandlerClassName()));     }     if (AprStatus.isAprAvailable() && AprStatus.getUseOpenSSL() &&             protocolHandler instanceof AbstractHttp11JsseProtocol) {         AbstractHttp11JsseProtocol<?> jsseProtocolHandler =                 (AbstractHttp11JsseProtocol<?>) protocolHandler;         if (jsseProtocolHandler.isSSLEnabled() &&                 jsseProtocolHandler.getSslImplementationName() == null) {             // OpenSSL is compatible with the JSSE configuration, so use it if APR is available             jsseProtocolHandler.setSslImplementationName(OpenSSLImplementation.class.getName());         }     }     try {         //2.2.1.1.1.5 初始化protocolHandler         protocolHandler.init();     } catch (Exception e) {         throw new LifecycleException(                 sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e);     } }

初始化protocolHandler

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public void init() throws Exception {     // Upgrade protocols have to be configured first since the endpoint     // init (triggered via super.init() below) uses this list to configure     // the list of ALPN protocols to advertise     // 必須先配置升級協議，因為端點初始化（通過下面的super.init()觸發）使用此列表來配置要發布的ALPN協議列表     for (UpgradeProtocol upgradeProtocol : upgradeProtocols) {         configureUpgradeProtocol(upgradeProtocol);     }     super.init(); }

Debug發現這個 upgradeProtocols 為空，直接走下面父類（AbstractProtocol）的 init 方法：

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public void init() throws Exception {     if (getLog().isInfoEnabled()) {         getLog().info(sm.getString("abstractProtocolHandler.init", getName()));         logPortOffset();     }     if (oname == null) {         // Component not pre-registered so register it         oname = createObjectName();         if (oname != null) {             Registry.getRegistry(null, null).registerComponent(this, oname, null);         }     }     if (this.domain != null) {         rgOname = new ObjectName(domain + ":type=GlobalRequestProcessor,name=" + getName());         Registry.getRegistry(null, null).registerComponent(                 getHandler().getGlobal(), rgOname, null);     }     String endpointName = getName();     endpoint.setName(endpointName.substring(1, endpointName.length()-1));     endpoint.setDomain(domain);     //2.2.1.1.1.6 初始化endpoint     endpoint.init(); }

上面又是一堆初始化，這個咱暫且不關注，注意最底下有一個 endpoint.init ：

初始化endpoint

來到 AbstractEndPoint ：

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public final void init() throws Exception {     // Debug為false     if (bindOnInit) {         bindWithCleanup();         bindState = BindState.BOUND_ON_INIT;     }     if (this.domain != null) {         // Register endpoint (as ThreadPool - historical name)         oname = new ObjectName(domain + ":type=ThreadPool,name="" + getName() + """);         Registry.getRegistry(null, null).registerComponent(this, oname, null);         ObjectName socketPropertiesOname = new ObjectName(domain +                 ":type=ThreadPool,name="" + getName() + "",subType=SocketProperties");         socketProperties.setObjectName(socketPropertiesOname);         Registry.getRegistry(null, null).registerComponent(socketProperties, socketPropertiesOname, null);         for (SSLHostConfig sslHostConfig : findSslHostConfigs()) {             registerJmx(sslHostConfig);         }     } }

這里面又是初始化 oname ，又是配置 socketProperties 的，但這里面再也沒見到 init 方法，證明這部分初始化過程已經結束了。

 初始化小結

嵌入式 Tomcat 的組件初始化步驟順序如下：

• Server
• Service
• Engine
• Executor
• MapperListener
• Connector
• Protocol
• EndPoint

startInternal：啟動Internal

startInternal 方法中有兩部分啟動：globalNamingResources 啟動，services 啟動。分別來看：

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protected void startInternal() throws LifecycleException {     // 發布啟動事件     fireLifecycleEvent(CONFIGURE_START_EVENT, null);     setState(LifecycleState.STARTING);     // 2.2.1.2.1 NamingResources啟動     globalNamingResources.start();     // Start our defined Services     synchronized (servicesLock) {         for (int i = 0; i < services.length; i++) {             // 2.2.1.2.2 Service啟動             services[i].start();         }     }     if (periodicEventDelay > 0) {         monitorFuture = getUtilityExecutor().scheduleWithFixedDelay(                 new Runnable() {                     @Override                     public void run() {                         startPeriodicLifecycleEvent();                     }                 }, 0, 60, TimeUnit.SECONDS);     } }

NamingResources啟動

只是發布事件和設置狀態而已

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protected void startInternal() throws LifecycleException {     fireLifecycleEvent(CONFIGURE_START_EVENT, null);     setState(LifecycleState.STARTING); }

Service啟動

依次啟動 Engine 、Executor 、MapperListener 、Connector 

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protected void startInternal() throws LifecycleException {     if(log.isInfoEnabled())         log.info(sm.getString("standardService.start.name", this.name));     setState(LifecycleState.STARTING);     // Start our defined Container first     if (engine != null) {         synchronized (engine) {             // 2.2.1.2.2.1 啟動Engine             engine.start();         }     }     synchronized (executors) {         for (Executor executor: executors) {             // 2.2.1.2.2.3 啟動Executor             executor.start();         }     }     // 2.2.1.2.2.4 啟動MapperListener     mapperListener.start();     // Start our defined Connectors second     synchronized (connectorsLock) {         for (Connector connector: connectors) {             // If it has already failed, don't try and start it             if (connector.getState() != LifecycleState.FAILED) {                 // 2.2.1.2.2.5 啟動connector                 connector.start();             }         }     } }

啟動Engine

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protected synchronized void startInternal() throws LifecycleException {     // Log our server identification information     if (log.isInfoEnabled()) {         log.info(sm.getString("standardEngine.start", ServerInfo.getServerInfo()));     }     // Standard container startup     super.startInternal(); }

它直接調的父類 ContainerBase 的 startInternal 方法：

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protected synchronized void startInternal() throws LifecycleException {     // Start our subordinate components, if any     logger = null;     getLogger();     // Cluster與集群相關，SpringBoot項目中使用嵌入式Tomcat，不存在集群     Cluster cluster = getClusterInternal();     if (cluster instanceof Lifecycle) {         ((Lifecycle) cluster).start();     }     // Realm與授權相關     Realm realm = getRealmInternal();     if (realm instanceof Lifecycle) {         ((Lifecycle) realm).start();     }     // Start our child containers, if any     // Container的類型是StandardHost     Container children[] = findChildren();     List<Future<Void>> results = new ArrayList<>();     for (int i = 0; i < children.length; i++) {         //異步初始化Host         results.add(startStopExecutor.submit(new StartChild(children[i])));     }     MultiThrowable multiThrowable = null;     for (Future<Void> result : results) {         try {             result.get();         } catch (Throwable e) {             log.error(sm.getString("containerBase.threadedStartFailed"), e);             if (multiThrowable == null) {                 multiThrowable = new MultiThrowable();             }             multiThrowable.add(e);         }     }     if (multiThrowable != null) {         throw new LifecycleException(sm.getString("containerBase.threadedStartFailed"),                 multiThrowable.getThrowable());     }     // Start the Valves in our pipeline (including the basic), if any     if (pipeline instanceof Lifecycle) {         ((Lifecycle) pipeline).start();     }     setState(LifecycleState.STARTING);     // Start our thread     if (backgroundProcessorDelay > 0) {         monitorFuture = Container.getService(ContainerBase.this).getServer()                 .getUtilityExecutor().scheduleWithFixedDelay(                         new ContainerBackgroundProcessorMonitor(), 0, 60, TimeUnit.SECONDS);     } }

StartChild 實現了帶返回值的異步多線程接口 Callable 核心方法就是在 call

1	private static class StartChild implements Callable<Void>

它實現了帶返回值的異步多線程接口 Callable ！那里面的核心方法就是 call ：

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public Void call() throws LifecycleException {     child.start();     return null; }

它在這里初始化 child，而通過Debug得知 child 的類型是 StandardHost，故來到 StandardHost 的 start 方法：

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protected synchronized void startInternal() throws LifecycleException {     // Set error report valve     String errorValve = getErrorReportValveClass();     if ((errorValve != null) && (!errorValve.equals(""))) {         try {             boolean found = false;             Valve[] valves = getPipeline().getValves();             for (Valve valve : valves) {                 if (errorValve.equals(valve.getClass().getName())) {                     found = true;                     break;                 }             }             if(!found) {                 Valve valve =                     (Valve) Class.forName(errorValve).getConstructor().newInstance();                 getPipeline().addValve(valve);             }         } catch (Throwable t) {             ExceptionUtils.handleThrowable(t);             log.error(sm.getString(                     "standardHost.invalidErrorReportValveClass",                     errorValve), t);         }     }     super.startInternal(); }

上面的一個大if結構是設置錯誤提示頁面的，下面又調父類的 startInternal ：

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protected synchronized void startInternal() throws LifecycleException {     // ......     // Start our child containers, if any     Container children[] = findChildren();     List<Future<Void>> results = new ArrayList<>();     for (int i = 0; i < children.length; i++) {         results.add(startStopExecutor.submit(new StartChild(children[i])));     }

又回來了。。。因為一個 Host 包含一個 Context 。

Host 搜索children就會搜到它下面的 Context ，之后又是下面的初始化過程，進入 Context 的初始化：

 啟動TomcatEmbeddedContext

在TomcatEmbeddedContext有如下組件被調用了 start 方法：

• StandardRoot
• DirResourceSet
• WebappLoader
• JarResourceSet
• StandardWrapper
• StandardPineline
• StandardWrapperValve
• NonLoginAuthenticator
• StandardContextValve
• StandardManager
• LazySessionIdGenerator

啟動Executor

但由于 Executor 沒有實現 startInternal 方法，所以不會啟動

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synchronized (executors) {     for (Executor executor: executors) {         executor.start();     } }

啟動MapperListener

接下來啟動 MapperListener ：

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public void startInternal() throws LifecycleException {     setState(LifecycleState.STARTING);     Engine engine = service.getContainer();     if (engine == null) {         return;     }     // 獲取當前部署的主機名（本地調試為localhost）     findDefaultHost();     // 把當前自身注冊到Engine、Host、Context、Wrapper中     addListeners(engine);     // 取出的Container的類型為Host     Container[] conHosts = engine.findChildren();     for (Container conHost : conHosts) {         Host host = (Host) conHost;         if (!LifecycleState.NEW.equals(host.getState())) {             // Registering the host will register the context and wrappers             //將Host、Context、Wrapper注冊到當前監聽器中             registerHost(host);         }     } }

 啟動Connector

最后一步是啟動 Connector 。

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// Start our defined Connectors second synchronized (connectorsLock) {     for (Connector connector: connectors) {         // If it has already failed, don't try and start it         if (connector.getState() != LifecycleState.FAILED) {             connector.start();         }     } }

 啟動總結

啟動過程依次啟動了如下組件：

• NamingResources
• Service
• Engine
• Host
• Context
• Wrapper
• Executor
• MapperListener

三、注冊Bean生命周期

3.1 WebServerStartStopLifecycle（Web服務器啟動-停止生命周期）

WebServerStartStopLifecycle實現了Lifecycle，在容器刷新完成時會調用finishRefresh()

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@Override public void start() {    //啟動Tomcat 容器    this.webServer.start();    this.running = true;    this.applicationContext          .publishEvent(new ServletWebServerInitializedEvent(this.webServer, this.applicationContext)); }

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public void start() throws WebServerException {     synchronized (this.monitor) {         if (this.started) {             return;         }         try {             // 3.1.1 還原、啟動Connector             addPreviouslyRemovedConnectors();             // 只拿一個Connector             Connector connector = this.tomcat.getConnector();             if (connector != null && this.autoStart) {                 // 3.1.2 延遲啟動                 performDeferredLoadOnStartup();             }             // 檢查Connector是否正常啟動             checkThatConnectorsHaveStarted();             this.started = true;             logger.info("Tomcat started on port(s): " + getPortsDescription(true) + " with context path '"                     + getContextPath() + "'");         }         // catch ......         finally {             // 解除ClassLoader與TomcatEmbeddedContext的綁定關系             Context context = findContext();             ContextBindings.unbindClassLoader(context, context.getNamingToken(), getClass().getClassLoader());         }     } }

3.1.1 addPreviouslyRemovedConnectors：啟動Connector

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private void addPreviouslyRemovedConnectors() {     Service[] services = this.tomcat.getServer().findServices();     for (Service service : services) {         Connector[] connectors = this.serviceConnectors.get(service);         if (connectors != null) {             for (Connector connector : connectors) {                 // 添加并啟動                 service.addConnector(connector);                 if (!this.autoStart) {                     stopProtocolHandler(connector);                 }             }             this.serviceConnectors.remove(service);         }     } }

可以發現它將一個緩存區的 Connector 一個一個取出放入 Service 中。注意在 service.addConnector 中有順便啟動的部分：

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public void addConnector(Connector connector) {     synchronized (connectorsLock) {         connector.setService(this);         Connector results[] = new Connector[connectors.length + 1];         System.arraycopy(connectors, 0, results, 0, connectors.length);         results[connectors.length] = connector;         connectors = results;     }     try {         if (getState().isAvailable()) {             // 啟動Connector             connector.start();         }     } catch (LifecycleException e) {         throw new IllegalArgumentException(                 sm.getString("standardService.connector.startFailed", connector), e);     }     // Report this property change to interested listeners     support.firePropertyChange("connector", null, connector); }

前面的部分是取出 Connector ，并與 Service 綁定，之后中間部分的try塊，會啟動 Connector ：

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protected void startInternal() throws LifecycleException {     // Validate settings before starting     if (getPortWithOffset() < 0) {         throw new LifecycleException(sm.getString(                 "coyoteConnector.invalidPort", Integer.valueOf(getPortWithOffset())));     }     setState(LifecycleState.STARTING);     try {         // 啟動ProtocolHandler         protocolHandler.start();     } catch (Exception e) {         throw new LifecycleException(                 sm.getString("coyoteConnector.protocolHandlerStartFailed"), e);     } }

Connector 的啟動會引發 ProtocolHandler 的啟動：

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public void start() throws Exception {     if (getLog().isInfoEnabled()) {         getLog().info(sm.getString("abstractProtocolHandler.start", getName()));         logPortOffset();     }     // 啟動EndPoint     endpoint.start();     monitorFuture = getUtilityExecutor().scheduleWithFixedDelay(             new Runnable() {                 @Override                 public void run() {                     if (!isPaused()) {                         startAsyncTimeout();                     }                 }             }, 0, 60, TimeUnit.SECONDS); }

ProtocolHandler 的啟動會引發 EndPoint 的啟動，至此所有組件均已啟動完畢。

 performDeferredLoadOnStartup：延遲啟動

這里面會延遲啟動 TomcatEmbeddedContext

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private void performDeferredLoadOnStartup() {     try {         for (Container child : this.tomcat.getHost().findChildren()) {             if (child instanceof TomcatEmbeddedContext) {                 // 延遲啟動Context                 ((TomcatEmbeddedContext) child).deferredLoadOnStartup();             }         }     }     catch (Exception ex) {         if (ex instanceof WebServerException) {             throw (WebServerException) ex;         }         throw new WebServerException("Unable to start embedded Tomcat connectors", ex);     } }

四、初始化上下文環境

這里在Spring中已經刷新過一次，詳情：在文章 https://www.jb51.net/article/277946.htm 的 prepareRefresh：初始化前的預處理中