spring mvc 总体启动流程

一、基础XML配置

1.WEB.xml配置如下

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"version="3.1"><display-name>Archetype Created Web Application</display-name><!--welcome pages--><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list><!--  <listener><listener-class>org.apache.logging.log4j.web.Log4jServletContextListener</listener-class></listener><filter><filter-name>log4jServletFilter</filter-name><filter-class>org.apache.logging.log4j.web.Log4jServletFilter</filter-class></filter><filter-mapping><filter-name>log4jServletFilter</filter-name><url-pattern>/*</url-pattern><dispatcher>REQUEST</dispatcher><dispatcher>FORWARD</dispatcher><dispatcher>INCLUDE</dispatcher><dispatcher>ERROR</dispatcher></filter-mapping>--><!--配置springmvc DispatcherServlet--><servlet><servlet-name>springMVC</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><!--配置dispatcher.xml作为mvc的配置文件--><param-name>contextConfigLocation</param-name><param-value>/dispatcher-servlet.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><!--<servlet>--><!--<servlet-name>EmpServlet</servlet-name>--><!--<servlet-class>com.gx.filter.EmpServlet</servlet-class>--><!--</servlet>--><servlet-mapping><servlet-name>springMVC</servlet-name><url-pattern>/</url-pattern></servlet-mapping><!--把applicationContext.xml加入到配置文件中--><context-param><param-name>contextConfigLocation</param-name><param-value>/applicationContext.xml</param-value></context-param><listener><listener-class>org.springframework.web.context.ContextLoaderListener</listener-class></listener><!--<listener>--><!--<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>--><!--</listener>--><!--    <context-param>-->
<!--        <param-name>log4jConfigLocation</param-name>-->
<!--        <param-value>classpath:log4j2.xml</param-value>-->
<!--    </context-param>--></web-app>

2.applicationContext.xml配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"><context:component-scan base-package="com.tpw.service"/></beans>

3.dispatcher-servlet.xml配置如下:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"xmlns:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"><!--此文件负责整个mvc中的配置--><!--启用spring的一些annotation --><context:annotation-config/><!-- 配置注解驱动 可以将request参数与绑定到controller参数上 --><mvc:annotation-driven><mvc:message-converters><bean class="org.springframework.http.converter.StringHttpMessageConverter"/><bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/></mvc:message-converters></mvc:annotation-driven><bean id="fastjson" class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter"><property name="supportedMediaTypes"><list><value>text/html;charset=UTF-8</value><value>application/json;charset=UTF-8</value></list></property></bean><!--静态资源映射--><!--本项目把静态资源放在了webapp的statics目录下，资源映射如下--><mvc:resources mapping="/css/**" location="/static/css/"/><mvc:resources mapping="/js/**" location="/static/js/"/><mvc:resources mapping="/image/**" location="/static/images/"/><mvc:default-servlet-handler/>  <!--这句要加上，要不然可能会访问不到静态资源，具体作用自行百度--><!-- 对模型视图名称的解析，即在模型视图名称添加前后缀(如果最后一个还是表示文件夹,则最后的斜杠不要漏了) 使用JSP--><!-- 默认的视图解析器 在上边的解析错误时使用 (默认使用html)- --><bean id="defaultViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"><property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/><property name="prefix" value="/WEB-INF/"/><!--设置JSP文件的目录位置--><property name="suffix" value=".jsp"/><property name="exposeContextBeansAsAttributes" value="true"/></bean><!-- 自动扫描装配 --><context:component-scan base-package="com.tpw.controller"/></beans>

二、tomcat容器引擎加载时首先加载web.xml所有配置的listener对象。\

1.我们配置的是

org.springframework.web.context.ContextLoaderListener，所有会加载此类contextInitialized方法，此方法会创建一个父类的applicationContext，加载applicationContext.xml文件中所有的扫描和配置的BEAN，并创建到容器工厂中。

 @Overridepublic void contextInitialized(ServletContextEvent event) {initWebApplicationContext(event.getServletContext());}

2.然后会调用org.springframework.web.context.ContextLoader.initWebApplicationContext，创建父类applicationContext,默认为org.springframework.web.context.support.XmlWebApplicationContext类环境。

public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {throw new IllegalStateException("Cannot initialize context because there is already a root application context present - " +"check whether you have multiple ContextLoader* definitions in your web.xml!");}servletContext.log("Initializing Spring root WebApplicationContext");Log logger = LogFactory.getLog(ContextLoader.class);if (logger.isInfoEnabled()) {logger.info("Root WebApplicationContext: initialization started");}long startTime = System.currentTimeMillis();try {// Store context in local instance variable, to guarantee that// it is available on ServletContext shutdown.if (this.context == null) {this.context = createWebApplicationContext(servletContext);}if (this.context instanceof ConfigurableWebApplicationContext) {ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;if (!cwac.isActive()) {// The context has not yet been refreshed -> provide services such as// setting the parent context, setting the application context id, etcif (cwac.getParent() == null) {// The context instance was injected without an explicit parent ->// determine parent for root web application context, if any.ApplicationContext parent = loadParentContext(servletContext);cwac.setParent(parent);}configureAndRefreshWebApplicationContext(cwac, servletContext);}}servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);ClassLoader ccl = Thread.currentThread().getContextClassLoader();if (ccl == ContextLoader.class.getClassLoader()) {currentContext = this.context;}else if (ccl != null) {currentContextPerThread.put(ccl, this.context);}if (logger.isInfoEnabled()) {long elapsedTime = System.currentTimeMillis() - startTime;logger.info("Root WebApplicationContext initialized in " + elapsedTime + " ms");}return this.context;}catch (RuntimeException | Error ex) {logger.error("Context initialization failed", ex);servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);throw ex;}}

3.创建完applicationContext后，则会contextLoader.configureAndRefreshWebApplicationContext去配置configlocation的XML，以及ID名称，然后调用applicationContext.refresh去实例化工厂中的对象。

 protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {if (ObjectUtils.identityToString(wac).equals(wac.getId())) {// The application context id is still set to its original default value// -> assign a more useful id based on available informationString idParam = sc.getInitParameter(CONTEXT_ID_PARAM);if (idParam != null) {wac.setId(idParam);}else {// Generate default id...wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +ObjectUtils.getDisplayString(sc.getContextPath()));}}wac.setServletContext(sc);String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);if (configLocationParam != null) {wac.setConfigLocation(configLocationParam);}// The wac environment's #initPropertySources will be called in any case when the context// is refreshed; do it eagerly here to ensure servlet property sources are in place for// use in any post-processing or initialization that occurs below prior to #refreshConfigurableEnvironment env = wac.getEnvironment();if (env instanceof ConfigurableWebEnvironment) {((ConfigurableWebEnvironment) env).initPropertySources(sc, null);}customizeContext(sc, wac);wac.refresh();}

4.application.refresh，则会根据applicationContext.xml中定义去扫描或者加载实例化BEAN，这个和spring ioc 原理一样.

三、org.springframework.web.servlet.DispatcherServlet初始化

1.DispatcherServlet静态代码执行,会将DispatcherServlet.properties配置的相应工厂SPI类配置读取出来到属性列表中。

包中的配置文件路径如下：

文件内容为:

# Default implementation classes for DispatcherServlet's strategy interfaces.
# Used as fallback when no matching beans are found in the DispatcherServlet context.
# Not meant to be customized by application developers.org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolverorg.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolverorg.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping,\org.springframework.web.servlet.function.support.RouterFunctionMappingorg.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter,\org.springframework.web.servlet.function.support.HandlerFunctionAdapterorg.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolverorg.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslatororg.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolverorg.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager

2.会调用org.springframework.web.servlet.HttpServletBean.init 进行初始化。创建一个

BeanWrapper属性包装器，里面包装的是DispatcherServlet对象。会将web.xml中

param-name中的值设置到DispatcherServlet对象的属性包装器中，如contextConfigLocation属性设置为dispatcher-servlet.xml。

 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;}}

3.调用FrameworkServlet.initServletBean去创建子applicationContext.

 protected final void initServletBean() throws ServletException {getServletContext().log("Initializing Spring " + getClass().getSimpleName() + " '" + getServletName() + "'");if (logger.isInfoEnabled()) {logger.info("Initializing Servlet '" + getServletName() + "'");}long startTime = System.currentTimeMillis();try {this.webApplicationContext = initWebApplicationContext();initFrameworkServlet();}catch (ServletException | RuntimeException ex) {logger.error("Context initialization failed", ex);throw ex;}if (logger.isInfoEnabled()) {logger.info("Completed initialization in " + (System.currentTimeMillis() - startTime) + " ms");}}

调用栈

4.初始化applicationContext时首先会获取父的applicationContext,然后会创建的子CONTEXT,

wac = createWebApplicationContext(rootContext);

 org.springframework.web.servlet.FrameworkServlet
protected WebApplicationContext initWebApplicationContext() {WebApplicationContext rootContext =WebApplicationContextUtils.getWebApplicationContext(getServletContext());WebApplicationContext wac = null;if (this.webApplicationContext != null) {// A context instance was injected at construction time -> use itwac = this.webApplicationContext;if (wac == null) {// No context instance was injected at construction time -> see if one// has been registered in the servlet context. If one exists, it is assumed// that the parent context (if any) has already been set and that the// user has performed any initialization such as setting the context idwac = findWebApplicationContext();}if (wac == null) {// No context instance is defined for this servlet -> create a local onewac = createWebApplicationContext(rootContext);}if (!this.refreshEventReceived) {// Either the context is not a ConfigurableApplicationContext with refresh// support or the context injected at construction time had already been// refreshed -> trigger initial onRefresh manually here.synchronized (this.onRefreshMonitor) {onRefresh(wac);}}if (this.publishContext) {// Publish the context as a servlet context attribute.String attrName = getServletContextAttributeName();getServletContext().setAttribute(attrName, wac);}return wac;}

5.创建新的子applicationContext,并调用其refresh方法。设置根applicationContext为父。后面的refresh就是扫描dispatch-servlet.xml中的所有配置包，然后加载和实例化到容器工厂中。

 protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {Class<?> contextClass = getContextClass();if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {throw new ApplicationContextException("Fatal initialization error in servlet with name '" + getServletName() +"': custom WebApplicationContext class [" + contextClass.getName() +"] is not of type ConfigurableWebApplicationContext");}ConfigurableWebApplicationContext wac =(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);wac.setEnvironment(getEnvironment());wac.setParent(parent);String configLocation = getContextConfigLocation();if (configLocation != null) {wac.setConfigLocation(configLocation);}configureAndRefreshWebApplicationContext(wac);return wac;}

四、DispatchServlet的onfresh加载流程

1.在上述子applicationContext.refresh调用完毕时，会调用publishEvent(new ContextRefreshedEvent(this))，而DispatcherServlet的父类FrameworkServlet有一个内部类实现了applicationListener接口

 private class ContextRefreshListener implements ApplicationListener<ContextRefreshedEvent> {@Overridepublic void onApplicationEvent(ContextRefreshedEvent event) {FrameworkServlet.this.onApplicationEvent(event);}}

2.最终会触发到DispatchServlet.onRefresh接口

3.最终会初始化springmvc中的各种策略类。这种会创建对象，注入属性。

 protected void initStrategies(ApplicationContext context) {initMultipartResolver(context);initLocaleResolver(context);initThemeResolver(context);initHandlerMappings(context);initHandlerAdapters(context);initHandlerExceptionResolvers(context);initRequestToViewNameTranslator(context);initViewResolvers(context);initFlashMapManager(context);}

最主要的是初始handlerMapping，即根据URL找到对应的handlerAdapter.

4.初始化handlerAdapter

排序后

5.初始化异常解析器

排序后

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