spring源码-4.注册bean的后处理器

迈不过友情╰ 2024-04-17 20:11 76阅读 0赞

执行完beanFactory的后处理器后，在实例化beanDefinition前，我们需要将bean的后处理器注册到容器中，这样才能在实例化beanDefinition的时候去执行这些后处理器。  
首先我们来看一下这个方法的入口（AbstractApplicationContext）：

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

进入registerBeanPostProcessors方法：

public static void registerBeanPostProcessors(
    			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
        //获取所有beanDefinition的类型为BeanPostProcessor的name
    	String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
    
    	//在prepareBeanFactory方法中，已经添加了三个，所以计算count的时候需要加上之前的和下面这个新增的
    	int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    	beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
        //用于记录实现priorityOrdered接口的后处理器
    	List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    	//用于记录内置的后处理器
    	List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
    	//用于记录实现ordered接口的后处理器
    	List<String> orderedPostProcessorNames = new ArrayList<>();
    	//用于记录剩余的后处理器
    	List<String> nonOrderedPostProcessorNames = new ArrayList<>();
    	//遍历之前通过type获取到的bean的后处理器，并进行分类
    	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);
    		}
    	}
    
        /**
        * 下面分三步将这些后处理器进行注册，这里有一个概念需要解释一下，MergedBeanDefinitionPostProcessor是
        * BeanPostProcessor的子接口，如果实现了MergedBeanDefinitionPostProcessor，则认为是一个内置的后处理器。
        */
    	//首先，将priorityOrdered类的进行排序，并注册
    	sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    	registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
    
    	//首先，将ordered类的进行排序，并注册
    	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);
    
    	//最后，将剩余的没有排序的后处理器进行注册
    	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);
    
    	//最后，对内置的后处理器进行排序，并注册
    	sortPostProcessors(internalPostProcessors, beanFactory);
    	registerBeanPostProcessors(beanFactory, internalPostProcessors);
    
    	//到这里，所有的bean的后处理器都已加入到beanFactory中了，这里再添加一个ApplicationListenerDetector后处理器
    	beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
    }