4_8.springboot2.x嵌入式servlet容器启动原理解析

客官°小女子只卖身不卖艺 2023-08-17 16:21 9阅读 0赞

**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![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2phdHBlbg_size_16_color_FFFFFF_t_70]  
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：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2phdHBlbg_size_16_color_FFFFFF_t_70 1]  
刷新容器：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2phdHBlbg_size_16_color_FFFFFF_t_70 2]  
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**

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