Spring 啓動記錄（5）

FrameworkServlet 設置XmlWebApplicationContext

一、

protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
   Class<?> contextClass = getContextClass();
   if (this.logger.isDebugEnabled()) {
      this.logger.debug("Servlet with name '" + getServletName() +
            "' will try to create custom WebApplicationContext context of class '" +
            contextClass.getName() + "'" + ", using parent context [" + parent + "]");
   }
   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);
   初始化完成後的流程
   wac.setEnvironment(getEnvironment());
   wac.setParent(parent);
   wac.setConfigLocation(getContextConfigLocation());

   configureAndRefreshWebApplicationContext(wac);

   return wac;
}

public void setConfigLocation(String location) {
   setConfigLocations(StringUtils.tokenizeToStringArray(location, CONFIG_LOCATION_DELIMITERS));
}

public void setConfigLocations(String... locations) {
   if (locations != null) {
      Assert.noNullElements(locations, "Config locations must not be null");
      this.configLocations = new String[locations.length];
      for (int i = 0; i < locations.length; i++) {
         this.configLocations[i] = resolvePath(locations[i]).trim();
      }
   }
   else {
      this.configLocations = null;
   }
}

protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
   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 information
      if (this.contextId != null) {
         wac.setId(this.contextId);
      }
      else {
         // Generate default id...
         wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
               ObjectUtils.getDisplayString(getServletContext().getContextPath()) + "/" + getServletName());
      }
   }

   wac.setServletContext(getServletContext());
   wac.setServletConfig(getServletConfig());
   wac.setNamespace(getNamespace());
   wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));

   // 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 #refresh
   ConfigurableEnvironment env = wac.getEnvironment();
   if (env instanceof ConfigurableWebEnvironment) {
      ((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
   }
   
   postProcessWebApplicationContext(wac);
   applyInitializers(wac);
   wac.refresh();
}

 

最後調用到refresh作真正的初始化動做（是父類AbstractApplicationContext模版方法）

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();
      }
   }
}

prepareRefresh:準備刷新動做

protected void prepareRefresh() {
   this.startupDate = System.currentTimeMillis();
   this.closed.set(false);
   this.active.set(true);

   if (logger.isInfoEnabled()) {
      logger.info("Refreshing " + this);
   }

   // Initialize any placeholder property sources in the context environment
  //初始化環境 ConfigurableEnvironment 的PropertySource
   initPropertySources();

   // Validate that all properties marked as required are resolvable
   // see ConfigurablePropertyResolver#setRequiredProperties
   //校驗是否有須要屬性沒有獲得
    //@Override
    //public void validateRequiredProperties() {
      //  MissingRequiredPropertiesException ex = new MissingRequiredPropertiesException();
     //   for (String key : this.requiredProperties) {
    //        if (this.getProperty(key) == null) {
   //             ex.addMissingRequiredProperty(key);
   //         }
  //      }
   //if (!ex.getMissingRequiredProperties().isEmpty()) {
   //     throw ex;
  //   }
  // }
   getEnvironment().validateRequiredProperties();

   // Allow for the collection of early ApplicationEvents,
   // to be published once the multicaster is available...
   this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>();
}

 

obtainFreshBeanFactory（父類AbstractApplicationContext的方法）：

得到最新信息的ApplicationContext

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
   refreshBeanFactory();
   ConfigurableListableBeanFactory beanFactory = getBeanFactory();
   if (logger.isDebugEnabled()) {
      logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
   }
   return beanFactory;
}

/**

此時到AbstractRefreshableApplicationContext（三級父類）的refreshBeanFactory方法中

protected final void refreshBeanFactory() throws BeansException {
   if (hasBeanFactory()) {//有工廠就關閉
      destroyBeans();
      closeBeanFactory();
   }
   try {
      //建立新的工廠類既是：DefaultListableBeanFactory（前面介紹講到初始化過程該類負責建立實例）
      DefaultListableBeanFactory beanFactory = createBeanFactory();
      beanFactory.setSerializationId(getId());
      customizeBeanFactory(beanFactory);
      //真正把xml數據加載到spring過程，
      //此時真正調用的是它的實現類XmlWebApplicationContext的loadBeanDefinitions
      loadBeanDefinitions(beanFactory);
      synchronized (this.beanFactoryMonitor) {
         this.beanFactory = beanFactory;
      }
   }
   catch (IOException ex) {
      throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
   }
}