4_8.springboot2.x嵌入式servlet容器启动原理解析

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问题描述:

什么时候创建嵌入式的Servlet容器工厂？

什么时候获取嵌入式的Servlet容器并启动Tomcat?

* 获取嵌入式的Servlet容器工厂：

1）、SpringBoot应用启动运行run方法

2）、refreshContext(context);SpringBoot刷新IOC容器【创建IOC容器对象，并初始化容器，创建容器中的每一个组件】；如果是web应用创建 AnnotationConfigServletWebServerApplicationContext ，否则： AnnotationConfigApplicationContext

a、创建容器并且判断：



刷新容器：



3）、refresh(context); 刷新刚才创建好的ioc容器；

public void refresh() throws BeansException, IllegalStateException {

		synchronized (this.startupShutdownMonitor) {

			// Prepare this context for refreshing.

			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.

			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// Prepare the bean factory for use in this context.

			prepareBeanFactory(beanFactory);

			try {

				// Allows post-processing of the bean factory in context subclasses.

				postProcessBeanFactory(beanFactory);

				// Invoke factory processors registered as beans in the context.

				invokeBeanFactoryPostProcessors(beanFactory);

				// Register bean processors that intercept bean creation.

				registerBeanPostProcessors(beanFactory);

				// Initialize message source for this context.

				initMessageSource();

				// Initialize event multicaster for this context.

				initApplicationEventMulticaster();

				// Initialize other special beans in specific context subclasses.

				onRefresh();

				// Check for listener beans and register them.

				registerListeners();

				// Instantiate all remaining (non-lazy-init) singletons.

				finishBeanFactoryInitialization(beanFactory);

				// Last step: publish corresponding event.

				finishRefresh();

			}

			catch (BeansException ex) {

				if (logger.isWarnEnabled()) {

					logger.warn("Exception encountered during context initialization - " +

							"cancelling refresh attempt: " + ex);

				}

				// Destroy already created singletons to avoid dangling resources.

				destroyBeans();

				// Reset 'active' flag.

				cancelRefresh(ex);

				// Propagate exception to caller.

				throw ex;

			}

			finally {

				// Reset common introspection caches in Spring's core, since we

				// might not ever need metadata for singleton beans anymore...

				resetCommonCaches();

			}

		}

	}

4）、 onRefresh(); web的ioc容器重写了onRefresh方法

5）、webioc容器会创建嵌入式的Servlet容器；** createWebServer();

6）、获取嵌入式的Servlet容器工厂

ServletWebServerFactory factory = getWebServerFactory();

从ioc容器中获取 ServletWebServerFactory**组件；

tomcatServletWebServerFactory 创建对象，后置处理器一看是这个对象，就获取所有的定制器来先定制Servlet容器的相关配置；

7）、 使用容器工厂获取嵌入式的Servlet容器 ：

this.webServer = factory.getWebServer(getSelfInitializer());

8）、嵌入式的Servlet容器创建对象并启动Servlet容器；

先启动嵌入式的Servlet容器，再将ioc容器中剩下没有创建出的对象获取出来；

IOC容器启动创建嵌入式的Servlet容器