目录准备工作启动接着往下看
目录
准备工作
我们知道SpringBoot的自动装配的秘密在 org.springframework.boot.autoconfigure 包下的 spring.factories 文件中，而嵌入Tomcat的原理就在这个文件中加载的一个配置类： org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration
@Configuration@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 {@Beanpublic 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);}/** * Registers a {@link WebServerFactoryCustomizerBeanPostProcessor}. Registered via * {@link ImportBeanDefinitionRegistrar} for early registration. */public static class BeanPostProcessorsRegistrarimplements ImportBeanDefinitionRegistrar, BeanFactoryAware {private ConfigurableListableBeanFactory beanFactory;@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {if (beanFactory instanceof ConfigurableListableBeanFactory) {this.beanFactory = (ConfigurableListableBeanFactory) beanFactory;}}@Overridepublic 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);}}}}
首先看一下上方的几个注解
@AutoConfigureOrder 这个注解是决定配置类的加载顺序的，当注解里的值越小越先加载，而 Ordered.HIGHEST_PRECEDENCE 的值是 Integer.MIN_VALUE 也就是说这个类肯定是最先加载的那一批 @ConditionalOnXXX 在之前的文章中已经无数次提到了，就不再阐述了 @EnableConfigurationProperties 开启 ServerProperties 类的属性值配置。而这个类里面包含的就是Web服务的配置
@ConfigurationProperties(prefix = "server", ignoreUnknownFields = true)public class ServerProperties {private Integer port;private InetAddress address;@NestedConfigurationPropertyprivate final ErrorProperties error = new ErrorProperties();private Boolean useForwardHeaders;private String serverHeader;private int maxHttpHeaderSize = 0; // bytesprivate Duration connectionTimeout;@NestedConfigurationPropertyprivate Ssl ssl;@NestedConfigurationPropertyprivate final Compression compression = new Compression();@NestedConfigurationPropertyprivate final Http2 http2 = new Http2();private final Servlet servlet = new Servlet();private final Tomcat tomcat = new Tomcat();private final Jetty jetty = new Jetty();private final Undertow undertow = new Undertow();}
这个类的代码太多了，这里就不一一贴出来了，我们平常在 application.properties 中配置的server.xxx就是这个类中属性
@ImportBeanPostProcessorsRegistrarpublic static class BeanPostProcessorsRegistrarimplements ImportBeanDefinitionRegistrar, BeanFactoryAware {@Overridepublic 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);}}}
这个类注册了两个bean： WebServerFactoryCustomizerBeanPostProcessor 和 ErrorPageRegistrarBeanPostProcessor 关于这两个bean的作用稍后再详细介绍
EmbeddedTomcat
@Configuration@ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })@ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)public static class EmbeddedTomcat { @Bean public TomcatServletWebServerFactory tomcatServletWebServerFactory() { return new TomcatServletWebServerFactory(); }}
这个类会在存在Tomcat相关jar包时添加一个 TomcatServletWebServerFactory bean
其他两个相信大家都知道怎么回事了
除了这些这个类还注入了两个类 ServletWebServerFactoryCustomizer 和 TomcatServletWebServerFactoryCustomizer现在前期准备工作已经做好了，看一下这个Tomcat是如何启动的吧
启动
启动入口在 ServletWebServerApplicationContext 中的 onRefresh 方法
protected void onRefresh() {super.onRefresh(); try { createWebServer(); }catch (Throwable ex) {throw new ApplicationContextException("Unable to start web server", ex);}}
Tomcat的启动就在 createWebServer 方法里面了
private void createWebServer() { WebServer webServer = this.webServer; ServletContext servletContext = getServletContext(); //第一次访问的时候两个对象都为空 if (webServer == null && servletContext == null) { ServletWebServerFactory factory = getWebServerFactory(); this.webServer = factory.getWebServer(getSelfInitializer()); } else if (servletContext != null) { try { getSelfInitializer().onStartup(servletContext); } catch (ServletException ex) { throw new ApplicationContextException("Cannot initialize servlet context", ex); } } initPropertySources();}
首先看一下 getWebServerFactory
protected ServletWebServerFactory getWebServerFactory() { // 这里获取的beanname就是上方注册的tomcatServletWebServerFactory了 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);}
准备环境里注册的bean现在出来一个了。注意，上方还注册了一个后置处理器 EmbeddedServletContainerCustomizerBeanPostProcessor ，获取bean tomcatServletWebServerFactory 的时候就会执行后置处理器的 postProcessBeforeInitialization 方法
public Object postProcessBeforeInitialization(Object bean, String beanName)throws BeansException {if (bean instanceof WebServerFactory) {postProcessBeforeInitialization((WebServerFactory) bean);}return bean;}private void postProcessBeforeInitialization(WebServerFactory webServerFactory) { LambdaSafe .callbacks(WebServerFactoryCustomizer.class, getCustomizers(), webServerFactory) .withLogger(WebServerFactoryCustomizerBeanPostProcessor.class) .invoke((customizer) -> customizer.customize(webServerFactory));}private Collection<WebServerFactoryCustomizer<?>> getCustomizers() { if (this.customizers == null) { // Look up does not include the parent context this.customizers = new ArrayList<>(getWebServerFactoryCustomizerBeans()); this.customizers.sort(AnnotationAwareOrderComparator.INSTANCE); this.customizers = Collections.unmodifiableList(this.customizers); } return this.customizers;}@SuppressWarnings({ "unchecked", "rawtypes" })private Collection<WebServerFactoryCustomizer<?>> getWebServerFactoryCustomizerBeans() { return (Collection) this.beanFactory .getBeansOfType(WebServerFactoryCustomizer.class, false, false).values();}
这个处理器的作用是获得所有定制器，然后执行定制器的方法
接着往下看
这个时候就可以启动Tomcat了
public WebServer getWebServer(ServletContextInitializer... initializers) { Tomcat tomcat = new Tomcat(); File baseDir = (this.baseDirectory != null ? this.baseDirectory : createTempDir("tomcat")); tomcat.setBaseDir(baseDir.getAbsolutePath()); Connector connector = new Connector(this.protocol); 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); } prepareContext(tomcat.getHost(), initializers); return getTomcatWebServer(tomcat);}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; initialize();}private void initialize() throws WebServerException { TomcatWebServer.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 this.tomcat.start(); // We can re-throw failure exception directly in the main thread 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 startDaemonAwaitThread(); } catch (Exception ex) { throw new WebServerException("Unable to start embedded Tomcat", ex); } }}
以上就是SpringBoot如何实现Tomcat自动配置的详细内容，更多关于SpringBoot实现Tomcat自动配置的资料请关注其它相关文章！
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