Spring源码-注册BeanPostProcessor

AbstractApplicationContext.java refresh方法

registerBeanPostProcessors(beanFactory);

protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
	PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}


public static void registerBeanPostProcessors(
		ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

	// WARNING: Although it may appear that the body of this method can be easily
	// refactored to avoid the use of multiple loops and multiple lists, the use
	// of multiple lists and multiple passes over the names of processors is
	// intentional. We must ensure that we honor the contracts for PriorityOrdered
	// and Ordered processors. Specifically, we must NOT cause processors to be
	// instantiated (via getBean() invocations) or registered in the ApplicationContext
	// in the wrong order.
	//
	// Before submitting a pull request (PR) to change this method, please review the
	// list of all declined PRs involving changes to PostProcessorRegistrationDelegate
	// to ensure that your proposal does not result in a breaking change:
	// https://github.com/spring-projects/spring-framework/issues?q=PostProcessorRegistrationDelegate+is%3Aclosed+label%3A%22status%3A+declined%22

	String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

	// Register BeanPostProcessorChecker that logs an info message when
	// a bean is created during BeanPostProcessor instantiation, i.e. when
	// a bean is not eligible for getting processed by all BeanPostProcessors.
	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<>();
	List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
	List<String> orderedPostProcessorNames = new ArrayList<>();
	List<String> nonOrderedPostProcessorNames = new ArrayList<>();
	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.
	sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
	registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

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

	// Now, register all regular BeanPostProcessors.
	List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
	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.
	sortPostProcessors(internalPostProcessors, beanFactory);
	registerBeanPostProcessors(beanFactory, internalPostProcessors);

	// Re-register post-processor for detecting inner beans as ApplicationListeners,
	// moving it to the end of the processor chain (for picking up proxies etc).
	beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

从beanFactory中获取所有BeanPostProcessor的bean，并按照PriorityOrdered，Ordered，没有实现Ordered的顺序排序后注册到beanFactory中，如果是MergedBeanDefinitionPostProcessor，则同时加到internalPostProcessors集合中，最后对internalPostProcessors集合排序，再将internalPostProcessors注册到beanFactory中。

MergedBeanDefinitionPostProcessor是BeanPostProcessor的子接口，提供了快速获取bean的所有指定信息和清理缓存中bean的信息的功能。

public interface MergedBeanDefinitionPostProcessor extends BeanPostProcessor {

/**
 * Post-process the given merged bean definition for the specified bean.
 * @param beanDefinition the merged bean definition for the bean
 * @param beanType the actual type of the managed bean instance
 * @param beanName the name of the bean
 * @see AbstractAutowireCapableBeanFactory#applyMergedBeanDefinitionPostProcessors
 */
void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName);

/**
 * A notification that the bean definition for the specified name has been reset,
 * and that this post-processor should clear any metadata for the affected bean.
 * <p>The default implementation is empty.
 * @param beanName the name of the bean
 * @since 5.1
 * @see DefaultListableBeanFactory#resetBeanDefinition
 */
default void resetBeanDefinition(String beanName) {
}

}