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本次主要介绍springmvc配置解析，更多源码解析文章请关注“天河聊技术”微信公众号。

springmvc配置解析

本次介绍org.springframework.web.context.ContextLoaderListener初始化，进入到这个方法org.springframework.web.context.ContextLoaderListener#contextInitialized，监听器收到一个servletContext上下文初始化完毕的事件后初始化WebApplicationContext，进入到这个方法org.springframework.web.context.ContextLoader#initWebApplicationContext

public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {//从servletContext中获取绑定key值是org.springframework.context.ApplicationContext.WebApplicationContext.ROOT的webApplicationContext对象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!");}      Log logger = LogFactory.getLog(ContextLoader.class);servletContext.log("Initializing Spring root WebApplicationContext");if (logger.isInfoEnabled()) {         logger.info("Root WebApplicationContext: initialization started");}      long startTime = System.currentTimeMillis();try {         // Store context in local instance variable, to guarantee that 将上下文存储在本地实例变量中，以保证这一点 // it is available on ServletContext shutdown.它在ServletContext关闭时可用。 if (this.context == null) {//创建web上下文 ->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 上下文尚未刷新—>提供了以下服务 // setting the parent context, setting the application context id, etc 设置父上下文、设置应用程序上下文id等等 if (cwac.getParent() == null) {                  // The context instance was injected without an explicit parent -> 上下文实例在没有显式父>的情况下被注入// determine parent for root web application context, if any.确定根web应用程序上下文的父级(如果有的话)。//->ApplicationContext parent = loadParentContext(servletContext);cwac.setParent(parent); }// 配置和刷新web上下文 -> configureAndRefreshWebApplicationContext(cwac, servletContext);}         }// web上下文绑定到servlet上下文中,key=org.springframework.web.context.WebApplicationContext.ROOT 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.isDebugEnabled()) {            logger.debug("Published root WebApplicationContext as ServletContext attribute with name [" +                  WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]"); }         if (logger.isInfoEnabled()) {            long elapsedTime = System.currentTimeMillis() - startTime;logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms"); }         return this.context;}      catch (RuntimeException ex) {         logger.error("Context initialization failed", ex); servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex); throw ex;}      catch (Error err) {         logger.error("Context initialization failed", err); servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err); throw err;}   }

进入到这个方法org.springframework.web.context.ContextLoader#createWebApplicationContext

protected WebApplicationContext createWebApplicationContext(ServletContext sc) {//找到web上下文初始化类 ->Class
     contextClass = determineContextClass(sc);if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {         throw new ApplicationContextException("Custom context class [" + contextClass.getName() +               "] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]");}//初始化web上下文return (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass); }

进入到这个方法org.springframework.web.context.ContextLoader#determineContextClass

protected Class
     determineContextClass(ServletContext servletContext) {//从servlet上下文获取contextClass属性值，指定web上下文的类String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);if (contextClassName != null) {         try {            return ClassUtils.forName(contextClassName, ClassUtils.getDefaultClassLoader()); }         catch (ClassNotFoundException ex) {            throw new ApplicationContextException(                  "Failed to load custom context class [" + contextClassName + "]", ex); }      }      else {// 如果servlet上下文没有配置这个属性值就从ContextLoader.properties这个配置文件中加载 -> contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName()); try {            return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader()); }         catch (ClassNotFoundException ex) {            throw new ApplicationContextException(                  "Failed to load default context class [" + contextClassName + "]", ex); }      }   }

找到这里

static {      // Load default strategy implementations from properties file.// This is currently strictly internal and not meant to be customized// by application developers.try {// 加载web上下文默认初始化类org.springframework.web.context.support.XmlWebApplicationContext从ContextLoader.properties这个配置文件 ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class); defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);}      catch (IOException ex) {         throw new IllegalStateException("Could not load 'ContextLoader.properties': " + ex.getMessage());}   }

往上返回到这个方法org.springframework.web.context.ContextLoader#loadParentContext

protected ApplicationContext loadParentContext(ServletContext servletContext) {      ApplicationContext parentContext = null;//从servlet上下文获取locatorFactorySelector参数值String locatorFactorySelector = servletContext.getInitParameter(LOCATOR_FACTORY_SELECTOR_PARAM);//从servlet上下文获取parentContextKey参数值String parentContextKey = servletContext.getInitParameter(LOCATOR_FACTORY_KEY_PARAM);if (parentContextKey != null) {         // locatorFactorySelector may be null, indicating the default "classpath*:beanRefContext.xml" locatorFactorySelector可以是null，表示默认的“classpath*:beanRefContext.xml” BeanFactoryLocator locator = ContextSingletonBeanFactoryLocator.getInstance(locatorFactorySelector); Log logger = LogFactory.getLog(ContextLoader.class); if (logger.isDebugEnabled()) {            logger.debug("Getting parent context definition: using parent context key of '" +                  parentContextKey + "' with BeanFactoryLocator"); }         this.parentContextRef = locator.useBeanFactory(parentContextKey); parentContext = (ApplicationContext) this.parentContextRef.getFactory();}      return parentContext; }

往上返回进入到这个方法org.springframework.web.context.ContextLoader#configureAndRefreshWebApplicationContext

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 应用程序上下文id仍然设置为其原始默认值 // -> assign a more useful id based on available information ->根据可用信息分配一个更有用的id// 从servlet上下文中获取contextId参数值 String 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);//从servlet上下文获取contextConfigLocation参数值 spring上下文的配置文件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 wac环境的#initPropertySources将在上下文中的任何情况下被调用// is refreshed; do it eagerly here to ensure servlet property sources are in place for 刷新;在这里急切地确保servlet属性源的位置是合适的吗// use in any post-processing or initialization that occurs below prior to #refresh 用于任何后处理或初始化中，发生在#刷新之前ConfigurableEnvironment env = wac.getEnvironment();if (env instanceof ConfigurableWebEnvironment) {// 初始化servlet参数 -> ((ConfigurableWebEnvironment) env).initPropertySources(sc, null);}//定制化spring上下文 ->customizeContext(sc, wac);//刷新spring上下文，这里在之前的spring源码解析中有详细介绍wac.refresh(); }

进入到这个方法org.springframework.web.context.ContextLoader#customizeContext

protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {//找到上下文初始化类 ->List
    
     
      
       >> initializerClasses =            determineContextInitializerClasses(sc);//判断上下文初始化类是否是ConfigurableWebApplicationContext类型for (Class
       
        
         > initializerClass : initializerClasses) {         Class
          initializerContextClass =               GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class); if (initializerContextClass != null && !initializerContextClass.isInstance(wac)) {            throw new ApplicationContextException(String.format(                  "Could not apply context initializer [%s] since its generic parameter [%s] " +                  "is not assignable from the type of application context used by this " +                  "context loader: [%s]", initializerClass.getName(), initializerContextClass.getName(),wac.getClass().getName())); }// 初始化上下文初始化类 this.contextInitializers.add(BeanUtils.instantiateClass(initializerClass));}      AnnotationAwareOrderComparator.sort(this.contextInitializers);for (ApplicationContextInitializer
         
           initializer : this.contextInitializers) {// 调用初始化器的初始化方法，初始化器可以自己实现 initializer.initialize(wac);} }
         
        
       
      
     
    

进入到这个方法org.springframework.web.context.ContextLoader#determineContextInitializerClasses

protected List
    
     
      
       >>         determineContextInitializerClasses(ServletContext servletContext) {      List
       
        
         
          >> classes = new ArrayList
          
           
            
             >>();//从servlet上下文中获取globalInitializerClasses参数值String globalClassNames = servletContext.getInitParameter(GLOBAL_INITIALIZER_CLASSES_PARAM);if (globalClassNames != null) { for (String className : StringUtils.tokenizeToStringArray(globalClassNames, INIT_PARAM_DELIMITERS)) {//加载初始化类，多个类用,或者;分开classes.add(loadInitializerClass(className)); } }//从servlet上下文获取contextInitializerClasses参数值String localClassNames = servletContext.getInitParameter(CONTEXT_INITIALIZER_CLASSES_PARAM);if (localClassNames != null) { for (String className : StringUtils.tokenizeToStringArray(localClassNames, INIT_PARAM_DELIMITERS)) {//加载初始化类，多个类用,或者;分开classes.add(loadInitializerClass(className)); } } return classes; }
            
           
          
         
        
       
      
     
    

往上返回到这个方法org.springframework.web.context.ContextLoaderListener#contextInitialized

说到最后

本次源码解析仅代表个人观点，仅供参考。