@Override

    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();

            }

        }

    }