public void refresh() throws BeansException, IllegalStateException {
  synchronized (this.startupShutdownMonitor) {
    StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
    // 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);
      StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
      // Invoke factory processors registered as beans in the context.
      invokeBeanFactoryPostProcessors(beanFactory);
      // Register bean processors that intercept bean creation.
      registerBeanPostProcessors(beanFactory);
      beanPostProcess.end();
      // 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) {
      // 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();
      contextRefresh.end();
    }
  }
}