八、Spring-registerBeanPostProcessors

// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);

这个方法比较简单,它主要是去找到实现BeanPostProcessor接口的类，按照保存PriorityOrdered、Ordered、NoOrdered的方式分类归并并排序。

但是也有也有几个别的任务去做：

1. 添加一个Bean类型检查器BeanPostProcessorChecker，去检测bean是否是基础bean类型。其实什么也没做就是打印个日志而已。
2. 收集BeanPostProcessor接口实现类，并进行归类排序。
3. 重新添加一个ApplicationListenerDetector监听器，为什么是重新？因为我们在准备beanfactory的时候已经添加过了，但是这里有可能bean的数量已经变化了，所以需要重新添加一次。

这个方法代码贴在下面：

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

	ApplicationContext
		
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);

		
		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

		
		List priorityOrderedPostProcessors = new ArrayList<>();
		List internalPostProcessors = new ArrayList<>();
		List orderedPostProcessorNames = new ArrayList<>();
		List 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 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 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));
	}

这里看一下BeanPostProcessor结构：

 

BeanPostProcessor：在bean的初始化前后进行调用的。

InstantiationAwareBeanPostProcessor：在实例化对象的前后过程以及实例的属性设置。

DestructionAwareBeanPostProcessor：在bean销毁前调用的。