[Java知识库]spring核心源码分析第十二篇 refresh流程之registerBeanPostProcessors

源码分析

• 将beanfactory中所有类型为BeanPostProcessor的beandefinition获取,通过getbean()得到实例
• 对这些BeanPostProcessor按继承Order接口类型分为3类,对分类进行sort
• 将所有BeanPostProcessor添加到beanfactory.beanPostProcessors属性
• beanPostProcessors为一个集合,允许重复添加,重复添加时,先删除存在后进行添加,核心目的保持排序

	public static void registerBeanPostProcessors(
			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
		获取前置阶段所有加载的beandefinition中类型为BeanPostProcessor的beandefinition的名称集合
		String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
		将其分为四类 优先级排序 排序  和普通  还有一个内部的[为前面三个中实现了MergedBeanDefinitionPostProcessor]
		List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();

		注册实现优先级排序相关接口的bean后置处理器
		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);
			}
		}
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

		注册实现排序相关接口的bean后置处理器
		List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
		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);

		注册普通的没有实现排序相关接口的bean后置处理器
		List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
		for (String ppName : nonOrderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			nonOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
		
		排序后注册MergedBeanDefinitionPostProcessor
		sortPostProcessors(internalPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, internalPostProcessors);

		// 最后注册一个ApplicationListener监听器,当一个bean是一个listener 在实例化时会被自动加入applicationcontext监听器集合
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
	}

常见的BeanPostProcessor

需要注意这三个bpp都实现了InstantiationAwareBeanPostProcessor

BeanPostProcessor分类

• SmartInstantiationAwareBeanPostProcessor
• InstantiationAwareBeanPostProcessor
• MergedBeanDefinitionPostProcessor
• DestructionAwareBeanPostProcessor
• BeanPostProcessor

总结

• 注册的BeanPostProcessors主要在实例化bean的时候完成bean的织入,增强,替换等功能
• BeanPostProcessors分为5类,如InstantiationAwareBeanPostProcessor等等,后面会专门有一篇文章讲解不同的BPP作用,这里主要了解,每一种bpp都有一些独有的特性[接口方法],作用于bean创建的各个阶段,有些作用在未加入bean工厂前,有些作用于已加入bean工厂