Spring之invokeBeanFactoryPostProcessors詳解

Spring的refresh的invokeBeanFactoryPostProcessors，就是調用全部註冊的、原始的BeanFactoryPostProcessor。

相關源碼

public static void invokeBeanFactoryPostProcessors(
		ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

	// Invoke BeanDefinitionRegistryPostProcessors first, if any.
	Set<String> processedBeans = new HashSet<String>();

	if (beanFactory instanceof BeanDefinitionRegistry) {
		...
		若是BeanFactory是BeanDefinitionRegistry類型，則特殊處理
		...
	}
	else {
		// Invoke factory processors registered with the context instance.
		// 調用用戶註冊的BeanFactoryPostProcessor
		invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
	}

	// Do not initialize FactoryBeans here: We need to leave all regular beans
	// uninitialized to let the bean factory post-processors apply to them!
	String[] postProcessorNames =
			beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

	// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
	// Ordered, and the rest.
	// 將BeanFactoryPostProcessor分開，分紅PriorityOrdered、Ordered、其餘類型
	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.
	// 首先調用實現PriorityOrdered類型的
	OrderComparator.sort(priorityOrderedPostProcessors);
	invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

	// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
	// 而後調用實現Ordered類型的
	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.
	// 最後調用其餘類型的
	List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
	for (String postProcessorName : nonOrderedPostProcessorNames) {
		nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
	}
	invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
}

BeanFactory是BeanDefinitionRegistry類型，則特殊處理

BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
List<BeanDefinitionRegistryPostProcessor> registryPostProcessors =
		new LinkedList<BeanDefinitionRegistryPostProcessor>();

// 區分通常的BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
	if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
		BeanDefinitionRegistryPostProcessor registryPostProcessor =
				(BeanDefinitionRegistryPostProcessor) postProcessor;
		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.
String[] postProcessorNames =
		beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);

// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
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);
	}
}
OrderComparator.sort(priorityOrderedPostProcessors);
registryPostProcessors.addAll(priorityOrderedPostProcessors);
invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry);

// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
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);

// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
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;
		}
	}
}

// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);

說明：

• 先處理用戶手動註冊的BeanFactoryPostProcessor，分爲BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor，而且BeanDefinitionRegistryPostProcessor會先調用其postXX方法
• 從容器獲取全部的BeanDefinitionRegistryPostProcessor類型，先處理實現PriorityOrdered類型的
• 再從容器獲取全部的BeanDefinitionRegistryPostProcessor類型，處理實現Ordered類型的
• 再從容器獲取全部的BeanDefinitionRegistryPostProcessor類型，處理剩下的，這裏有個遞歸，知道全部的BeanDefinitionRegistryPostProcessor都處理完
• BeanDefinitionRegistryPostProcessor也是BeanFactoryPostProcessor，最後處理BeanDefinitionRegistryPostProcessor從BeanFactoryPostProcessor繼承的方法
• 最後處理通常的BeanFactoryPostProcessor的postXXX方法

PS：BeanDefinitionRegistryPostProcessor有可能會動態新增新的BeanDefinitionRegistryPostProcessor，全部這裏每次都從容器中從新得到全部的BeanDefinitionRegistryPostProcessor。



PS：BeanDefinitionRegistryPostProcessor的回調方法，先於BeanFactoryPostProcessor的回調方法執行。

/**
 * Invoke the given BeanDefinitionRegistryPostProcessor beans.
 */
private static void invokeBeanDefinitionRegistryPostProcessors(
		Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {

	for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
		postProcessor.postProcessBeanDefinitionRegistry(registry);
	}
}

/**
 * Invoke the given BeanFactoryPostProcessor beans.
 */
private static void invokeBeanFactoryPostProcessors(
		Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {

	for (BeanFactoryPostProcessor postProcessor : postProcessors) {
		postProcessor.postProcessBeanFactory(beanFactory);
	}
}