传统tomcat启动服务与springboot启动内置tomcat服务的区别(推荐)_Tomcat

spring整合springmvc

spring整合springmvc中web.xml配置如下，tomcat在启动过程中会加载web.xml中的内容，ContextLoaderListener实现了tomcat里面的ServletContextListener接口，所以在tomcat容器启动过程通过ContextLoaderListener来进行spring容器的初始化操作，并将classpath:spring/applicationContext-*.xml指定下的spring配置文件加载，该配置文件我只配置了<context:component-scan base-package=“org.com.yp”/>，代表通过扫描org.com.yp包下的类，包含@Component @Controller@Service等注解等类，进行bean注册。
bean注册是通过AbstractXmlApplicationContext.loadBeanDefinitions该类的方法进行bean定义加载的。

spring中加载bean定义是在org.springframework.context.ConfigurableApplicationContext#refresh方法中的ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory()方法加载bean的，该方法之后会调用org.springframework.context.support.AbstractRefreshableApplicationContext#refreshBeanFactory方法创建bean工厂，并加载的bean定义。

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									<?xml version="1.0" encoding="UTF-8"?>

									<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

									         xmlns="http://java.sun.com/xml/ns/javaee"

									         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

									                             http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

									  <display-name>Archetype Created Web Application</display-name>

									  <listener>

									    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>

									  </listener>

									  <!-- 加载spring容器 -->

									  <context-param>

									    <param-name>contextConfigLocation</param-name>

									    <param-value>classpath:spring/applicationContext-*.xml</param-value>

									  </context-param>

									​

									  <servlet>

									    <servlet-name>mvc-dispatcher</servlet-name>

									    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

									    <!-- 配置springMVC需要加载的配置文件-->

									    <init-param>

									      <param-name>contextConfigLocation</param-name>

									      <param-value>classpath:spring/spring-*.xml</param-value>

									    </init-param>

									  </servlet>

									​

									  <servlet-mapping>

									    <servlet-name>mvc-dispatcher</servlet-name>

									    <!-- 默认匹配所有的请求 -->

									    <url-pattern>/</url-pattern>

									  </servlet-mapping>

									</web-app>

当tomcat容器启动后，通过路径访问资源时，第一次会调用org.springframework.web.servlet.HttpServletBean#init方法，之后的http请求就不会再方法该方法类；HttpServletBean实现了Servlet接口的规范，所以经过浏览器的请求经过servlet接口初始化执行init方法时，会再从spring容器中去加载springmvc配置中定义的加载类，spring与springmvc是父子容器的关系，下面是HttpServletBean的init方法

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									public final void init() throws ServletException {

									        // Set bean properties from init parameters.

									        PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);

									        if (!pvs.isEmpty()) {

									            try {

									                BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);

									                ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());

									                bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));

									                initBeanWrapper(bw);

									                bw.setPropertyValues(pvs, true);

									            }

									            catch (BeansException ex) {

									                if (logger.isErrorEnabled()) {

									                    logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);

									                }

									                throw ex;

									            }

									        }

									        // 最后会调用org.springframework.context.ConfigurableApplicationContext#refresh容器的刷新方法，

									        // 进行springmvc容器初始化

									        initServletBean();

									    }

									    }

springboot启动容器

springboot启动的方式则是先在springboot的org.springframework.boot.SpringApplication#run(java.lang.String…)方法中就初始化了spring的上下文环境(里面包含bean工厂)，之后通过org.springframework.boot.SpringApplication#refreshContext方法调用Spring容器中的ConfigurableApplicationContext#refresh方法初始化bean.
在spring与springmvc整合的环境中，bean定义的加载是在org.springframework.context.support.AbstractApplicationContext#obtainFreshBeanFactory方法，而springboot中是在

org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors方法，该方法中通过ConfigurationClassPostProcessor类去加载bean定义，该类实现了BeanDefinitionRegistryPostProcessor接口，这个接口允许对bean定义进行加工处理。

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									// spring中的BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子接口，

									// BeanFactoryPostProcessor的作用是在bean的定义信息已经加载但还没有初始化的时候执行方法postProcessBeanFactory(）方法，

									// 而BeanDefinitionRegistryPostProcessor是在BeanFactoryPostProcessor的前面执行，在源码

									// org.springframework.context.support.PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors()方法里面定义了执行顺序

									// BeanFactoryPostProcessor是bean工厂的bean属性处理容器，说通俗一些就是可以管理我们的bean工厂内所有的beandefinition（未实例化）数据，可以随心所欲的修改属性。

									public void refresh() throws BeansException, IllegalStateException {

									        synchronized (this.startupShutdownMonitor) {

									            prepareRefresh();

									            //获取告诉子类初始化Bean工厂 将bean加载到缓存中 spring springmvc整合是在这初始化bean的

									            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

									            prepareBeanFactory(beanFactory);

									​

									            try {

									                postProcessBeanFactory(beanFactory);

									​

									                // springboot容器启动加载到这时，初始化了下面几个bean name

									                //0 = "org.springframework.context.annotation.internalConfigurationAnnotationProcessor" =》对应ConfigurationClassPostProcessor类

									                //1 = "org.springframework.context.annotation.internalAutowiredAnnotationProcessor" =》 AutowiredAnnotationBeanPostProcessor

									                //2 = "org.springframework.context.annotation.internalCommonAnnotationProcessor" =》 CommonAnnotationBeanPostProcessor

									                //3 = "org.springframework.context.event.internalEventListenerProcessor" =》 EventListenerMethodProcessor

									                //4 = "org.springframework.context.event.internalEventListenerFactory" =》 DefaultEventListenerFactory

									                // 调用我们的bean工厂的后置处理器.加载bean定义（不是实例化）,通过ConfigurationClassPostProcessor去加载启动类中的扫描路径

									                // 然后将路径下到bean加载进来

									                invokeBeanFactoryPostProcessors(beanFactory);

									​

									                registerBeanPostProcessors(beanFactory);

									​

									                initMessageSource();

									​

									                initApplicationEventMulticaster();

									​

									                // 这个方法同样也是留个子类实现的springboot也是从这个方法进行启动tomat的.

									                onRefresh();

									​

									                registerListeners();

									​

									                //实例化我们剩余的单实例bean.

									                finishBeanFactoryInitialization(beanFactory);

									​

									                // 最后容器刷新 发布刷新事件(Spring cloud也是从这里启动的)

									                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();

									            }

									        }

									    }