Spring ClassPathXmlApplicationContext bean参数替换及init单例初始化

ClassPathXmlApplicationContext 的bean参数替换及init 单例的核心代码
是public abstract class AbstractApplicationContext的如下函数：

@Override
	public void refresh() throws BeansException, IllegalStateException {
		 
			// 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.getApplicationStartup().start("spring.context.beans.post-process");
				// Invoke factory processors registered as beans in the context.
				invokeBeanFactoryPostProcessors(beanFactory);
				//TODO  beanFactory beanFactory.destroyBean(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.
				// 实例化所有单例对象
				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();
				 
			}
		 
	}

xml里面的类似id=" s i m p l e . i d " c l a s s = " {simple.id}" class=" simple.id"class="{simple.class}" 被替换为properties里面simple.id=springSimpleJob
发生在：invokeBeanFactoryPostProcessors(beanFactory);

实际被调用代码为类PropertySourcesPlaceholderConfigurer的如下函数：

@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		if (this.propertySources == null) {
			this.propertySources = new MutablePropertySources();
			if (this.environment != null) {
				this.propertySources.addLast(
					new PropertySource<Environment>(ENVIRONMENT_PROPERTIES_PROPERTY_SOURCE_NAME, this.environment) {
						@Override
						@Nullable
						public String getProperty(String key) {
							return this.source.getProperty(key);
						}
					}
				);
			}
			try {
				PropertySource<?> localPropertySource =
						new PropertiesPropertySource(LOCAL_PROPERTIES_PROPERTY_SOURCE_NAME, mergeProperties());
				if (this.localOverride) {
					this.propertySources.addFirst(localPropertySource);
				}
				else {
					this.propertySources.addLast(localPropertySource);
				}
			}
			catch (IOException ex) {
				throw new BeanInitializationException("Could not load properties", ex);
			}
		}

		processProperties(beanFactory, new PropertySourcesPropertyResolver(this.propertySources));
		this.appliedPropertySources = this.propertySources;
	}

调用stack如下：

PropertySourcesPlaceholderConfigurer.postProcessBeanFactory(ConfigurableListableBeanFactory) line: 129	
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(Collection<BeanFactoryPostProcessor>, ConfigurableListableBeanFactory) line: 325	
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory, List<BeanFactoryPostProcessor>) line: 183	
		ClassPathXmlApplicationContext(AbstractApplicationContext).invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory) line: 746	
		ClassPathXmlApplicationContext(AbstractApplicationContext).refresh() line: 564	
		ClassPathXmlApplicationContext.<init>(String[], boolean, ApplicationContext) line: 144	
		ClassPathXmlApplicationContext.<init>(String) line: 85	
		SpringMain.main(String[]) line: 125	
	Thread [Thread-0] (Running)	
	Daemon Thread [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:5181] (Running)	
	Thread [SessionTracker] (Running)	
	Thread [SyncThread:0] (Running)	
	Thread [ProcessThread(sid:0 cport:-1):] (Running)		

而单例的初始化为finishBeanFactoryInitialization(beanFactory);，在执行finishBeanFactoryInitialization(beanFactory)前所有bean只是保存为内存对象，不会初始化。