Spring源码情操陶冶-AbstractApplicationContext#invokeBeanFactoryPostProcessors

阅读源码有利于陶冶情操，承接前文Spring源码情操陶冶-AbstractApplicationContext#postProcessBeanFactory

约定：web.xml中配置的contextClass为XmlWebApplicationContext

瞧瞧官方注释

	/**
	 * Instantiate and invoke all registered BeanFactoryPostProcessor beans,
	 * respecting explicit order if given.
	 * <p>Must be called before singleton instantiation.必须在单例实例化前调用
	 */

主要是实例化和调用所有已注册的BeanFactoryPostProcessors beans

源码简析

对应的代码清单如下

	//通过一个委托类来处理实例化调用
	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
	}

PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors

简单的看下委托类中的此方法源码，代码清单如下

public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
		// 第一步，Invoke BeanDefinitionRegistryPostProcessors first, if any.
		Set<String> processedBeans = new HashSet<String>();
		//条件满足
		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
			List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
			List<BeanDefinitionRegistryPostProcessor> registryPostProcessors =
					new LinkedList<BeanDefinitionRegistryPostProcessor>();
			//刚开始进来beanFactoryPostProcessors为空
			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				//BeanDefinitionRegistryPostProcessor目前该接口的实现者为MapperScannerConfigurer/ConfigurationClassPostProcessor
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
					BeanDefinitionRegistryPostProcessor registryPostProcessor =
							(BeanDefinitionRegistryPostProcessor) postProcessor;
					//调用postProcessBeanDefinitionRegistry接口，比如MapperScannerConfigurer则会进行扫描注册接口bean操作
					registryPostProcessor.postProcessBeanDefinitionRegistry(registry);
					registryPostProcessors.add(registryPostProcessor);
				}
				else {
					regularPostProcessors.add(postProcessor);
				}
			}
			// Do not initialize FactoryBeans here: We need to leave all regular beans
			// uninitialized to let the bean factory post-processors apply to them!
			// Separate between BeanDefinitionRegistryPostProcessors that implement
			// PriorityOrdered, Ordered, and the rest.
			//寻找实现了BeanDefinitionRegistryPostProcessor接口类的beans
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.这里只有ConfigurationClassPostProcessor类才操作
			List<BeanDefinitionRegistryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			***
			省略部分代码
			***
			// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
			invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}
		else {
			// Invoke factory processors registered with the context instance.
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}
		//第二步，处理注册在bean工厂中BeanFactoryPostProcessor接口实现类并调用公用的方法，比如PropertyResourceConfigurer资源文件解析类
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest. 执行的优先权
		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);
			}
		}
		***
		省略部分代码
		***
	}

主要功能是对实现BeanFactoryPostProcessor的bean类进行调用公共接口方法postProcessBeanFactory,并相关的信息可关联至ConfigurableListableBeanFactorybeanFactory。常见的使用类为PropertyPlaceholderConfigurer文件解析类、MapperScannerConfigurer SQL接口注册类。公共接口的调用前者会对每个bean对象含有${}进行解析替换，后者会注册mapper class接口类并尝试解析注解

下节预告

Spring源码情操陶冶-AbstractApplicationContext#registerBeanPostProcessors