spring的Bean加载过程

1、找准入口 ,使用ClassPathXmlApplicationContext加载配置文件，用于加载classPath下的配置文件

//第一行，执行完成之后就完成了spring配置文件的加载，刷新spring上下文
ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext(
				"classpath:spring-mvc.xml");
//获取实例Bean
Person person=context.getBean("person",Person.class);

ClassPathXmlApplicationContext的继承关系如下：

2、现在开始仔细分析第一句，可以看出第一句就已经完成了spring配置文件的加载

ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext(
				"classpath:spring-mvc.xml");

3、查看classPathXmlApplicationContext的源码，下面表格是对象

4、从构造方法可以看出，加载spring配置文件实际调用的是如下构造方法：

public ClassPathXmlApplicationContext(String[] configLocations,boolean refresh, ApplicationContext parent)
			throws BeansException {
		//设置父级的ApplicationContext，null
		super(parent);
    	//1.设置配置文件的路径， 2. 将路径中的占位符${placeholder}使用系统的变量替换
		setConfigLocations(configLocations);
		if (refresh) {
			refresh();
		}
	}

5、进入setConfigLocations(configLocations);的源码，这个方法是父类AbstractRefreshableConfigApplicationContext中的方法

1. 设置配置文件的路径
2. 替换路径中的占位符`${placeholder}`为系统变量中的值

//locations : 配置文件路径-+
public void setConfigLocations(String[] locations){
		if (locations != null) {
            //断言
			Assert.noNullElements(locations, "Config locations must not be null");
            //存储配置文件路径的数组，存储去掉占位符后的文件路径数组
			this.configLocations = new String[locations.length];
            //遍历locations，解析占位符
			for (int i = 0; i < locations.length; i++) {
                	//调用resolvePath解析占位符
				this.configLocations[i] = resolvePath(locations[i]).trim();
			}
		}
		else {
			this.configLocations = null;
		}
	}

6、进入resolvePath的源码可以知道，实际上执行的是AbstractPropertyResolver的doResolvePlaceholders方法，如下

/**
* text : 需要解析的路径
* PropertyPlaceholderHelper ： 这个是解析系统占位符的辅助类，主要用来将占位符替换成系统的环境变量
*/
private String doResolvePlaceholders(String text, PropertyPlaceholderHelper helper){
    	//调用PropertyPlaceholderHelper类中的replacePlaceholders方法
		return helper.replacePlaceholders(text, new PropertyPlaceholderHelper.PlaceholderResolver() {
			public String resolvePlaceholder(String placeholderName){
				return getPropertyAsRawString(placeholderName);
			}
		});
	}

7、 进入 PropertyHelpe r中的 replacePlaceholders 方法 ，实际上调用 org.springframework.util.PropertyPlaceholderHelper 这个类的 parseStringValue 解析占位符

1. 实际调用的是 parseStringValue 方法
2. this.placeholderPrefix这个是占位符的前缀 ${,在创建PropertyHelper的时候就已经指定了占位符的placeholderPrefix=”${“ ,placeholderSuffix=”}”,valueSeparator=”:”
3. 使用parseStringValue方法递归解析占位符中的内容
4. 在 parseStringValue 方法中使用两次递归
   1. placeholder = parseStringValue(placeholder, placeholderResolver, visitedPlaceholders); ,这个是第一次，用来解析占位符中的placeholder是否还包含占位符，如果有占位符需要将其抽离出来，去掉 ${}
   2. propVal = parseStringValue(propVal, placeholderResolver, visitedPlaceholders); ，这个是第二次递归调用，用来解析 propVal 中的占位符

public String replacePlaceholders(String value, PlaceholderResolver placeholderResolver){
		Assert.notNull(value, "Argument 'value' must not be null.");
    	//调用的是parseStringValue方法
		return parseStringValue(value, placeholderResolver, new HashSet<String>());
	}

/**
* strVal  ： 需要解析的字符串，就是配置文件的路径
* placeholderResolver ： 策略接口，占位符解析器
* visitedPlaceholders ： 存储已经访问过的占位符
**/
protected String parseStringValue(
			String strVal, PlaceholderResolver placeholderResolver, Set<String> visitedPlaceholders) {
		//将strval转换成StringBuilder，便于后续到操作
		StringBuilder buf = new StringBuilder(strVal);
	
    //this.placeholderPrefix这个是占位符的前缀 ${,在创建PropertyHelper的时候就已经指定了占位符的placeholderPrefix="${" ,placeholderSuffix="}",valueSeparator=":"
	//获取前缀在这个配置文件路径中的开始索引
		int startIndex = strVal.indexOf(this.placeholderPrefix);
    
		while (startIndex != -1) {
            //占位符前缀在路径中的结束索引
			int endIndex = findPlaceholderEndIndex(buf, startIndex);
            
            //如果结束索引存在
			if (endIndex != -1) {
                
                //此时取出${plcaeholder}中的占位符内容placeholder
				String placeholder = buf.substring(startIndex + this.placeholderPrefix.length(), endIndex);
                
                //保存取出来的占位符内容placeholder
				String originalPlaceholder = placeholder;
                
                //如果占位符中的内容已经被访问过了，抛出出异常返回，递归结束的条件
				if (!visitedPlaceholders.add(originalPlaceholder)) {
					throw new IllegalArgumentException(
							"Circular placeholder reference '" + originalPlaceholder + "' in property definitions");
				}
				
                //递归解析已经取出的占位符中的内容 palceholder
				placeholder = parseStringValue(placeholder, placeholderResolver, visitedPlaceholders);
                
				
                //这个最重要的一步，将解析占位符内容placeholder的值，比如将java.version转换成1.8.0_60
				String propVal = placeholderResolver.resolvePlaceholder(placeholder);
                
				if (propVal == null && this.valueSeparator != null) {
					int separatorIndex = placeholder.indexOf(this.valueSeparator);
					if (separatorIndex != -1) {
						String actualPlaceholder = placeholder.substring(0, separatorIndex);
						String defaultValue = placeholder.substring(separatorIndex + this.valueSeparator.length());
						propVal = placeholderResolver.resolvePlaceholder(actualPlaceholder);
						if (propVal == null) {
							propVal = defaultValue;
						}
					}
				}
                //如果解析出来的占位符不为空，比如${java.version}将被解析成 1.8.0_60
				if (propVal != null) {
					//此时继续递归解析出1.8.0_60中的占位符
					propVal = parseStringValue(propVal, placeholderResolver, visitedPlaceholders);
                    //将路径中的占位符替换成系统变量的值，比如将${java.version} 替换成 1.8.0_60
					buf.replace(startIndex, endIndex + this.placeholderSuffix.length(), propVal);
					if (logger.isTraceEnabled()) {
						logger.trace("Resolved placeholder '" + placeholder + "'");
					}
                    //继续在路径字符串中剩余的子串中查找占位符，如果有占位符，那么还会继续解析占位符
					startIndex = buf.indexOf(this.placeholderPrefix, startIndex + propVal.length());
				}
				else if (this.ignoreUnresolvablePlaceholders) {
					// Proceed with unprocessed value.
					startIndex = buf.indexOf(this.placeholderPrefix, endIndex + this.placeholderSuffix.length());
				}
				else {
					throw new IllegalArgumentException("Could not resolve placeholder '" +
							placeholder + "'" + " in string value /"" + strVal + "/"");
				}
                //将已转换成功的占位符从以访问的集合中移除即可
				visitedPlaceholders.remove(originalPlaceholder);
			}
			else {
				startIndex = -1;
			}
		}

		return buf.toString();   //将解析完成之后的配置文件返回
	}

8、总之一句话 ： setConfigLocations(configLocations);的作用就是将客户端传入的配置文件路径，先解析占位符，之后将解析完成之后的配置文件路径存储起来

9、现在进入ClassPathXmlApplicationContext中的refresh方法，实际上调用的是父类org.springframework.context.support.AbstractApplicationContext的方法，下面我们一个一个方法分析

//刷新spring上下文
public void refresh()throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			//在刷新之前设置一些参数，比如设置开始时间戳，上下文是否激活的标志，输出刷新上下文的信息，验证一些必要的属性
			prepareRefresh();

			//需要创建beanFactory，如果已经存在beanFactory，那么关闭，详细其请看 10
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// 准备上下文工厂，详情见12
			prepareBeanFactory(beanFactory);

			try {
				//允许子类向后置处理器添加组件
				postProcessBeanFactory(beanFactory);

				// 调用BeanFactoryPostProcessor和BeanDefintionRegistoryPostProcessor这两个后置处理器
				invokeBeanFactoryPostProcessors(beanFactory);

				// 注册BeanPostProcessor,用来拦截bean的创建，详情见 14
				registerBeanPostProcessors(beanFactory);

				//初始化消息源
				initMessageSource();

				// 初始化应用程序事件广播器，用户可以自定义一个事件广播器，如果用户没有定义，那么使用默认的事件广播器SimpleApplicationEventMulticaster
				initApplicationEventMulticaster();

				// 在其他子类中初始化bean
				onRefresh();

				// 检测事件监听器
				registerListeners();

				//完成实例化剩余的单例(non-lazy-init)
				finishBeanFactoryInitialization(beanFactory);

				// 完成刷新，初始化生命周期处理器......
				finishRefresh();
			}

			catch (BeansException ex) {
				// Destroy already created singletons to avoid dangling resources.
				destroyBeans();

				// Reset 'active' flag.
				cancelRefresh(ex);

				// Propagate exception to caller.
				throw ex;
			}
		}
	}

10、进入 obtainFreshBeanFactory ，分析源码

//AbastractApplicationContext的方法
protected ConfigurableListableBeanFactory obtainFreshBeanFactory(){
    	//实际刷新上下文的方法，这个方法就是实际的刷新上下文方法，其中会调用loadBeanDefinitions(beanFactory);加载配置文件中的内容到BeanDefiniton中
		refreshBeanFactory();
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (logger.isDebugEnabled()) {
			logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
		}
		return beanFactory;
	}


	//org.springframework.context.support.AbstractRefreshableApplicationContext中的方法
	//AbstractApplicationContext的子类中的方法
	@Override
	protected final void refreshBeanFactory()throws BeansException {
        //如果其中有beanfactory，那么销毁
		if (hasBeanFactory()) {
			destroyBeans();
			closeBeanFactory();
		}
		
        try {
            //重新创建一个beanFactory
			DefaultListableBeanFactory beanFactory = createBeanFactory();
            //设置序列化id
			beanFactory.setSerializationId(getId());
            
            //定制beanFactory，设置相关属性，包括是否允许覆盖名称的不同定义的对象及循环依赖以及
			//设置@Autowired和@Qualifier，注解解析器QualifierAnnotationAutowireCandidateResolver
			customizeBeanFactory(beanFactory);
            //加载BeanDefine 详情见 11
			loadBeanDefinitions(beanFactory);
			synchronized (this.beanFactoryMonitor) {
				this.beanFactory = beanFactory;
			}
		}
		catch (IOException ex) {
			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
		}
	}

11、 进入 loadBeanDefinitions(beanFactory); 方法

​ 1、 主要调用的是XmlBeanDefinitionReader其中的loadBeanDefinitions方法，详情请看我的spring之BeanDefinitonReader解析

//这个是org.springframework.context.support.AbstractXmlApplicationContext类中的方法
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)throws BeansException, IOException {
       
	//创建要给beanDefinitionReader，用于读取BeanDefinition
       //详情见 BeanDefinitonReader的源码解析
	XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

	//配置XmlBeanDefinitionReader
	beanDefinitionReader.setEnvironment(this.getEnvironment());
	beanDefinitionReader.setResourceLoader(this);	
	beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

	initBeanDefinitionReader(beanDefinitionReader);
       //加载BeanDefiniton，主要的功能从配置文件中读取BeanDefiniton注册到注册表中
	loadBeanDefinitions(beanDefinitionReader);
}

12、prepareBeanFactory ：准备BeanFactory，目前还不太明白，后续分析

//准备BeanFactory，设置一些参数，比如后置处理器，
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory){
		//设置类加载器
		beanFactory.setBeanClassLoader(getClassLoader());
    	
    //设置表达式解析器，用来解析BeanDefiniton中的带有表达式的值
		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
    	
    
		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

		// 配置后置处理器，主要的作用就是在spring实例化bean的前后做一些操作
		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    	
    	//忽略自动装配的类，这些类都不能使用@Resource或者@Autowired自动装配获取对象
		beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
		beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
		beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
		beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

		//注册可解析的自动装配类
		beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
		beanFactory.registerResolvableDependency(ResourceLoader.class, this);
		beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
		beanFactory.registerResolvableDependency(ApplicationContext.class, this);

		//在添加一个应用程序监听器
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

		//检查这些类是否被
		if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));

			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
		}

		// 将下面这些类注册到容器中，使用registerSingleton方法注册，我们可以直接从容器中获取这些类的对象使用
		if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
			beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
		}
		if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
			beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
		}
		if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
			beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
		}
	}

13、调用BeanFactory的后置处理器，主要的功能就是调用注册在容器中的BeanFactoryPostProcessor和BeanDefinitionRegistoryPostProcessor

​ 1、 BeanFactoryPostProcessor 这个是后置处理器，实现这个类可以修改容器中bean的数据信息，可以在spring配置文件加载之后执行，在单例实例化之前调用，因此可以在其中修改和获取bean的实例化的信息，通过 BeanDefintion

​ 2、先调用 BeanDefinitionRegistryPostProcessor ，按照优先级调用，比如分为实现PriorityOrdered这个接口和Orderd这个接口的，分开调用

​ 3、再调用实现BeanFactoryPostProcessor这个接口的，也是按照优先级别调用，和上面的流程一样

//实例化和调用BeanFactory后置处理器，必须在单例实例化之前调用
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory){
    	//调用后置处理器注册委托类的方法调用，getBeanFactoryPostProcessors用于获取注册的全部的BeanFactoryPostProcessor
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
	}

//实际的调用方法，PostProcessorRegistrationDelegate中的方法
public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

		// Invoke BeanDefinitionRegistryPostProcessors first, if any.
		Set<String> processedBeans = new HashSet<String>();
		
    	//如果beanFactory是BeanDefinitionRegistry的子类，BeanDefinitionRegistry使用来向注册表中注册Bean的元信息的(BeanDefintion)
		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            
            //存放BeanFactoryPostProcessor
			List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
            
            //存放BeanDefinitionRegistryPostProcessor
			List<BeanDefinitionRegistryPostProcessor> registryPostProcessors =
					new LinkedList<BeanDefinitionRegistryPostProcessor>();
            
			//遍历。判断是否是BeanDefinitionRegistryPostProcessor实例
			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryPostProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
                    
                    	//调用BeanDefinitionRegistryPostProcessor
					registryPostProcessor.postProcessBeanDefinitionRegistry(registry);
                    //添加
					registryPostProcessors.add(registryPostProcessor);
				}
				else {
                    //表示这个是BeanFactoryPostProcessor实例，添加进集合
					regularPostProcessors.add(postProcessor);
				}
			}

			//--- 根据类型类型获取beanFactory中注册的BeanDefinitionRegistryPostProcessor的bean的所有名称数组
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);

			// ---- 首先调用的是BeanDefinitionRegistryPostProcessor类型的后置处理器
            
            //存放实现PriorityOrdered这个接口的BeanDefinitionRegistryPostProcessor
			List<BeanDefinitionRegistryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
            
            //遍历，如果实现了PriorityOrdered这个接口就保存下来
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
            
            //按照优先级排序
			OrderComparator.sort(priorityOrderedPostProcessors);
            //添加进入集合
			registryPostProcessors.addAll(priorityOrderedPostProcessors);
            
            //首先调用实现PriorityOrdered这个接口的BeanDefinitionRegistryPostProcessor
			invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry);

			// ---- 下面是调用实现Orderd这个接口的BeanDefinitionRegistryPostProcessor
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			List<BeanDefinitionRegistryPostProcessor> orderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					orderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			OrderComparator.sort(orderedPostProcessors);
			registryPostProcessors.addAll(orderedPostProcessors);
			invokeBeanDefinitionRegistryPostProcessors(orderedPostProcessors, registry);

            
			// ---- 最终调用剩余全部的BeanDefinitionRegistryPostProcessor
            
			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					if (!processedBeans.contains(ppName)) {
						BeanDefinitionRegistryPostProcessor pp = beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class);
						registryPostProcessors.add(pp);
						processedBeans.add(ppName);
						pp.postProcessBeanDefinitionRegistry(registry);
						reiterate = true;
					}
				}
			}

			// 调用BeanFactoryPostProcessor接口中的方法，因为BeanDefitionRegistory继承了这个接口
			invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {
			// Invoke factory processors registered with the context instance.
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}

		//--- 下面是调用实现BeanFactoryPostProcessor接口的类，和上面的流程一样
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
		List<String> orderedPostProcessorNames = new ArrayList<String>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
		for (String ppName : postProcessorNames) {
			if (processedBeans.contains(ppName)) {
				// skip - already processed in first phase above
			}
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
		OrderComparator.sort(priorityOrderedPostProcessors);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		OrderComparator.sort(orderedPostProcessors);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// Finally, invoke all other BeanFactoryPostProcessors.
		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
		for (String postProcessorName : nonOrderedPostProcessorNames) {
			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
	}

14、注册BeanPostProcessor，用来拦截Bean的创建，这个接口可以实现在Bean初始化和初始化之后执行相关的操作，会有单独一篇解读

​ 1、这个注册BeanPostProcessor思想和上面的调用BeanFactoryPostProcessor的思想一样，按照优先级注册，通过判断是否实现PriorityOrdered和orderd接口，按照优先级排序注册到BeanFactory中，其实注册的方法就是将这个后置处理器添加到beanFactory中的 List<BeanPostProcessor> beanPostProcessors = new ArrayList<BeanPostProcessor>()

//依然这里依然调用的PostProcessorRegistrationDelegate，其中包含了注册后置处理器和调用后置处理器的方法，相当于一个代理人
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory){
		PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
	}

//PostProcessorRegistrationDelegate中的注册BeanPostProcessors的方法
//其中beanFactory这个新创建的beanFactory，其中的BeanPostProcessor都没有注册，applicationContext这个是之前创建的，其中的处理器已经注册过了
public static void registerBeanPostProcessors(
			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
		
    	//根据类型新加载全部的BeanFactoryProcessor的类，
		String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

		//创建BeanPostProcessor检测器
		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

		// Separate between BeanPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
		List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
		List<String> orderedPostProcessorNames = new ArrayList<String>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
		for (String ppName : postProcessorNames) {
			if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
				priorityOrderedPostProcessors.add(pp);
				if (pp instanceof MergedBeanDefinitionPostProcessor) {
					internalPostProcessors.add(pp);
				}
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, register the BeanPostProcessors that implement PriorityOrdered.
		OrderComparator.sort(priorityOrderedPostProcessors);
		registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

		// Next, register the BeanPostProcessors that implement Ordered.
		List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
		for (String ppName : orderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			orderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		OrderComparator.sort(orderedPostProcessors);
		registerBeanPostProcessors(beanFactory, orderedPostProcessors);

		// Now, register all regular BeanPostProcessors.
		List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
		for (String ppName : nonOrderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			nonOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

		// Finally, re-register all internal BeanPostProcessors.
		OrderComparator.sort(internalPostProcessors);
		registerBeanPostProcessors(beanFactory, internalPostProcessors);

		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
	}

总结

1、入口

ClassPathXmlApplicationContext context=new ClassPathXmlApplicationContext("spring-test.xml");

2、解析传入的路径中的占位符，集合 org.springframework.core.env.AbstractPropertyResolver 和 org.springframework.util.PropertyPlaceholderHelper

3、刷新上下文

​ 1、 prepareRefresh() : 准备刷新，设置一些活动标志，比如开始时间，当前的状态

​ 2、 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory() ：从spring的配置文件中加载bean，封装成BeanDefinition，注册到注册表中，创建beanFactory

​ 3、 prepareBeanFactory(beanFactory); ：准备BeanFactory，设置累加载器，添加后置处理器，SPL表达式解析器，向ioc容器中注入一些组件

​ 4、 postProcessBeanFactory(beanFactory); ： 允许子类做一些处理操作

​ 5、 invokeBeanFactoryPostProcessors(beanFactory); ：调用BeanFactoryProcessor，先是调用BeanDefitionRegistoyPostProcessor,之后调用BeanFactoryProcessor

​ 6、 registerBeanPostProcessors(beanFactory); ： 将配置文件中读取的Bean的后置处理器注册到容器中

​ 7、 initMessageSource(); ：初始化消息源，用于国际化

​ 8、 initApplicationEventMulticaster() ： 初始化事件广播器，判断容器中是否已经注册了该组件，如果没有该组件，那么使用默认的

​ 9、 onRefresh(); ：子类初始化一些特殊的bean

​ 10、 registerListeners(); ：注册事件监听器

​ 11、 finishBeanFactoryInitialization(beanFactory) ：完成初始化，初始化非懒加载的bean

​ 12、 finishRefresh(); ：完成刷新，最后一步，初始化生命周期处理器，派发事件

参考文章

• https://blog.csdn.net/turkeyzhou/article/category/365505/2
• https://www.evget.com/article/2016/2/23/23576.html
• http://www.cnblogs.com/killbug/p/6087648.html