【SpringBoot】SpringBoot内置Servlet容器源码分析-Tomcat

自动装配加载 ServletWebServerFactoryAutoConfiguration

在自动装配的时候，会加载spring.factories，并且添加到IOC容器中。这里包含web自动配置类ServletWebServerFactoryAutoConfiguration ，其中本类中注入三个bean，分别是EmbeddedTomcat\EmbeddedJetty\EmbeddedUndertow, 以及可以添加自定义BD的BeanPostProcessorsRegistrar

@Configuration(proxyBeanMethods = false) // 配置类
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE) // 自动装配的顺序
@ConditionalOnClass(ServletRequest.class) //  引入Servlet的依赖才生效
@ConditionalOnWebApplication(type = Type.SERVLET) // 当Web容器是Servlet才生效
@EnableConfigurationProperties(ServerProperties.class) // 关联对应的属性配置类
// 通过 @Import注解引入一些Web容器
@Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,// 引入一些对应的容器的类对象ServletWebServerFactoryConfiguration.EmbeddedJetty.class,ServletWebServerFactoryConfiguration.EmbeddedUndertow.class })
public class ServletWebServerFactoryAutoConfiguration {/*** 这里注入了一个ServletWebServer的定制工厂* @param serverProperties* @return*/@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 BeanPostProcessorsRegistrar implements 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;}// 向容器中注册了一个后置处理器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);}}}}

初始化和启动 tomcat

在ioc容器刷新时候，进行自定义拓展，实现tomcat的创建。

	protected void onRefresh() {super.onRefresh();try {createWebServer();}catch (Throwable ex) {throw new ApplicationContextException("Unable to start reactive web server", ex);}}// tomcat执行private void createWebServer() {WebServer webServer = this.webServer;ServletContext servletContext = getServletContext();if (webServer == null && servletContext == null) {ServletWebServerFactory factory = getWebServerFactory();// 获取WebServer的工厂对象this.webServer = factory.getWebServer(getSelfInitializer()); // 获取具体的WebServer}else if (servletContext != null) {try {getSelfInitializer().onStartup(servletContext);}catch (ServletException ex) {throw new ApplicationContextException("Cannot initialize servlet context", ex);}}initPropertySources();}// 获取tomcat工厂  调用getBean会进行初始化、实例化操作protected ServletWebServerFactory getWebServerFactory() {// Use bean names so that we don't consider the hierarchyString[] 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);}

创建tomcat对象

	public WebServer getWebServer(ServletContextInitializer... initializers) {if (this.disableMBeanRegistry) {Registry.disableRegistry();}Tomcat tomcat = new Tomcat();// 创建Tomcat容器，并且配置连接器，引擎等属性File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");tomcat.setBaseDir(baseDir.getAbsolutePath());Connector connector = new Connector(this.protocol);// 创建连接器connector.setThrowOnFailure(true);// 给service添加connectortomcat.getService().addConnector(connector);// 定制自己的连接器customizeConnector(connector);// 设置到tomcat中tomcat.setConnector(connector);// 自动部署 falsetomcat.getHost().setAutoDeploy(false);configureEngine(tomcat.getEngine()); // 配置Enginefor (Connector additionalConnector : this.additionalTomcatConnectors) {tomcat.getService().addConnector(additionalConnector);// Service关联Connector}prepareContext(tomcat.getHost(), initializers);return getTomcatWebServer(tomcat); // 获取TomcatWebServer}public TomcatWebServer(Tomcat tomcat, boolean autoStart) {Assert.notNull(tomcat, "Tomcat Server must not be null");this.tomcat = tomcat;this.autoStart = autoStart;initialize(); // 非常重要的初始化方法 ⭐️}// 启动Tomcat通过发布事件触发一些Listener的初始化  也只是完成tomcat的初始化工作this.tomcat.start();// 启动tomcatprotected void finishRefresh() {super.finishRefresh();WebServer webServer = startWebServer();if (webServer != null) {publishEvent(new ServletWebServerInitializedEvent(webServer, this));}}