Spring源码（八）reflush的invokeBeanFactoryPostProcessors方法

invokeBeanFactoryPostProcessors方法

BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor子类。

BeanDefinitionRegistry是对beanDefinition的增删改操作的。而BeanFactoryPostProcessor则对beanFactory操作的类。

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

        Set<String> processedBeans = new HashSet<>();

        if (beanFactory instanceof BeanDefinitionRegistry) {

            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

            List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();

            List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                // 如果是BeanDefinitionRegistryPostProcessor
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                    BeanDefinitionRegistryPostProcessor registryProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;

                    registryProcessor.postProcessBeanDefinitionRegistry(registry);

                    registryProcessors.add(registryProcessor);
                } else {

                    regularPostProcessors.add(postProcessor);
                }
            }

            List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();


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

            for (String ppName : postProcessorNames) {
                if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                }
            }
            // 按照优先级进行排序操作
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            // 添加到registryProcessors中，用于最后执行postProcessBeanFactory方法
            registryProcessors.addAll(currentRegistryProcessors);
            // 遍历currentRegistryProcessors，执行postProcessBeanDefinitionRegistry方法
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 执行完毕之后，清空currentRegistryProcessors
            currentRegistryProcessors.clear();

            // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
            // 调用所有实现Ordered接口的BeanDefinitionRegistryPostProcessor实现类
            // 找到所有实现BeanDefinitionRegistryPostProcessor接口bean的beanName，
            // 此处需要重复查找的原因在于上面的执行过程中可能会新增其他的BeanDefinitionRegistryPostProcessor
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                    // 获取名字对应的bean实例，添加到currentRegistryProcessors中
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                }
            }
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            registryProcessors.addAll(currentRegistryProcessors);
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            currentRegistryProcessors.clear();

            // 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)) {
                        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                        processedBeans.add(ppName);
                        reiterate = true;
                    }
                }
                sortPostProcessors(currentRegistryProcessors, beanFactory);
                registryProcessors.addAll(currentRegistryProcessors);
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                currentRegistryProcessors.clear();
            }

            // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
            invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
            invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        } else {
            // Invoke factory processors registered with the context instance.
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
        }

        // 到这里为止，入参beanFactoryPostProcessors和容器中的所有BeanDefinitionRegistryPostProcessor已经全部处理完毕，下面开始处理容器中
        // 所有的BeanFactoryPostProcessor
        // 可能会包含一些实现类，只实现了BeanFactoryPostProcessor，并没有实现BeanDefinitionRegistryPostProcessor接口

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

        // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
        // Ordered, and the rest.
        // 用于存放实现了PriorityOrdered接口的BeanFactoryPostProcessor
        List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
        // 用于存放实现了Ordered接口的BeanFactoryPostProcessor的beanName
//		List<String> orderedPostProcessorNames = new ArrayList<>();
        List<BeanFactoryPostProcessor> orderedPostProcessor = new ArrayList<>();
        // 用于存放普通BeanFactoryPostProcessor的beanName
//		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
        List<BeanFactoryPostProcessor> nonOrderedPostProcessorNames = new ArrayList<>();
        // 遍历postProcessorNames,将BeanFactoryPostProcessor按实现PriorityOrdered、实现Ordered接口、普通三种区分开
        for (String ppName : postProcessorNames) {
            // 跳过已经执行过的BeanFactoryPostProcessor
            if (processedBeans.contains(ppName)) {
                // skip - already processed in first phase above
            }
            // 添加实现了PriorityOrdered接口的BeanFactoryPostProcessor到priorityOrderedPostProcessors
            else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
            // 添加实现了Ordered接口的BeanFactoryPostProcessor的beanName到orderedPostProcessorNames
            else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
//				orderedPostProcessorNames.add(ppName);
                orderedPostProcessor.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            } else {
                // 添加剩下的普通BeanFactoryPostProcessor的beanName到nonOrderedPostProcessorNames
//				nonOrderedPostProcessorNames.add(ppName);
                nonOrderedPostProcessorNames.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
        }

        // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
        // 对实现了PriorityOrdered接口的BeanFactoryPostProcessor进行排序
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        // 遍历实现了PriorityOrdered接口的BeanFactoryPostProcessor，执行postProcessBeanFactory方法
        invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

        // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
        // 创建存放实现了Ordered接口的BeanFactoryPostProcessor集合
//		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
        // 遍历存放实现了Ordered接口的BeanFactoryPostProcessor名字的集合
//		for (String postProcessorName : orderedPostProcessorNames) {
        // 将实现了Ordered接口的BeanFactoryPostProcessor添加到集合中
//			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
//		}
        // 对实现了Ordered接口的BeanFactoryPostProcessor进行排序操作
//		sortPostProcessors(orderedPostProcessors, beanFactory);
        sortPostProcessors(orderedPostProcessor, beanFactory);
        // 遍历实现了Ordered接口的BeanFactoryPostProcessor，执行postProcessBeanFactory方法
//		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(orderedPostProcessor, beanFactory);

        // Finally, invoke all other BeanFactoryPostProcessors.
        // 最后，创建存放普通的BeanFactoryPostProcessor的集合
//		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
        // 遍历存放实现了普通BeanFactoryPostProcessor名字的集合
//		for (String postProcessorName : nonOrderedPostProcessorNames) {
        // 将普通的BeanFactoryPostProcessor添加到集合中
//			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
//		}
        // 遍历普通的BeanFactoryPostProcessor，执行postProcessBeanFactory方法
//		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(nonOrderedPostProcessorNames, beanFactory);

        // Clear cached merged bean definitions since the post-processors might have
        // modified the original metadata, e.g. replacing placeholders in values...
        // 清除元数据缓存（mergeBeanDefinitions、allBeanNamesByType、singletonBeanNameByType）
        // 因为后置处理器可能已经修改了原始元数据，例如，替换值中的占位符
        beanFactory.clearMetadataCache();
    }

    /**
     * 注册beanPostProcessor
     * @param beanFactory
     * @param applicationContext
     */

首先我们看下参数，这里有个beanFactoryPostProcessors，实际上是上一层方法的getBeanFactoryPostProcessors传过来的，所以一定会有addBeanFactoryPostProcessor，这里就是我们外部自定义的BeanFactoryPostProcessor。
下面我们自定义一个外部的beanFactoryPostProcessor

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

        System.out.println("2222222222222222");
    }
}

我们可以看到已经注入进来了，可以被识别到。
这里的注入可以写bean，class为MyBeanFactoryPostProcessor。也可以在customizeBeanFactory用 super.addBeanFactoryPostProcessor(new MyBeanFactoryPostProcessor());方式添加。
但是实际上测试效果，如果写bean方式，那么不会走额外的外部postprocssor，而是走所有实现BeanFactoryPostProcessor类的方法，这个是个注意点。故，如果想整个流程都跟一下，包括外部的BeanFactoryPostProcessor，应该在customizeBeanFactory里设置。原因是需要add后再get。

代码看上去很多，其实实际上是一个顺序的问题，上面这幅图已经显示了一部分的顺序，代码基本上都是基于上面流程来的。下面写一下具体的流程。
首先判断beanFactory是否是BeanDefinitionRegistry，一般都是的，因为beanFactory一般为defaultListableBeanFactory，默认为BeanDefinitionRegistry，所以都会进这个判断里来。然后会先先处理外部的beanFactoryPostProcessors，这个时候会判断如果是BeanDefinitionRegistryPostProcessor，那么就直接处理掉了，再把这个对象放进registryProcessors集合中。如果不是，那么放进regularPostProcessors中，到后面统一处理beanFactoryPostProcessor。
然后判断是否是内部的BeanDefinitionRegistryPostProcessor，这个时候按照PriorityOrdered、Orderd与为实现排序进行。这里会将对象加入到 registryProcessors，用于最后执行postProcessBeanFactory方法，而BeanDefinitionRegistryPostProcessors则直接执行掉。最后用BeanFactoryPostProcessors处理regularPostProcessors与registryProcessors集合中对象的postProcessBeanFactory方法。

继续，，入参beanFactoryPostProcessors和容器中的所有BeanDefinitionRegistryPostProcessor已经全部处理完毕，下面开始处理容器中所有的BeanFactoryPostProcessor
这里直接定义三个集合，分别是 priorityOrdered、ordered、未排序的集合，将对象加入到里面，再到最后统一进行postProcessorBeanFactory的处理。

总结