【Spring boot】整合tomcat底层原理( 三 ) _生活百科

这个方法会调用createWebServer()方法。

// 最核心的俩行代码private void createWebServer() { ...... // 获取web容器，多个或者没有的时候报错 ServletWebServerFactory factory = getWebServerFactory(); // 调用这个容器的getWebServer方法，上面的启动tomcat的方法！ this.webServer = factory.getWebServer(getSelfInitializer()); ......}

getWebServerFactory控制项目组有且只能有一个web容器！

protected ServletWebServerFactory getWebServerFactory() { // Use bean names so that we don't consider the hierarchy // 得到所有类型为ServletWebServerFactory的Bean 。TomcatServletWebServerFactory、JettyServletWebServerFactory、UndertowServletWebServerFactory都是他得到子类！ String[] beanNames = getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class); // 不存在，报错 if (beanNames.length == 0) { throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean."); } // 存在不止一个，报错！ if (beanNames.length > 1) { throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to multiple ServletWebServerFactory beans : " + StringUtils.arrayToCommaDelimitedString(beanNames)); } // 返回唯一的一个web容器！ return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class);}获取tomcat的配置

自动配置类ServletWebServerFactoryAutoConfiguration上除了import三个web容器，还import了BeanPostProcessorsRegistrar 。
BeanPostProcessorsRegistrar实现了ImportBeanDefinitionRegistrar，所以他会在spring启动的时候调用registerBeanDefinitions方法。
registerBeanDefinitions会注册一个Bean：webServerFactoryCustomizerBeanPostProcessor 。

public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) { // Bean工厂，一个Aware回调进行赋值 if (this.beanFactory == null) { return; } // 注册webServerFactoryCustomizerBeanPostProcessor这个Bean 。 registerSyntheticBeanIfMissing(registry, "webServerFactoryCustomizerBeanPostProcessor", WebServerFactoryCustomizerBeanPostProcessor.class, WebServerFactoryCustomizerBeanPostProcessor::new); // 注册errorPageRegistrarBeanPostProcessor registerSyntheticBeanIfMissing(registry, "errorPageRegistrarBeanPostProcessor", ErrorPageRegistrarBeanPostProcessor.class, ErrorPageRegistrarBeanPostProcessor::new);}