SpringBoot启动源码解读（5）

Spring会支持自定义的BeanFactoryPostProcessor，这些Processor是在PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory, List<BeanFactoryPostProcessor>) 里面执行，其代码如下：

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

    // Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set processedBeans =new HashSet();
    if (beanFactoryinstanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
      List regularPostProcessors =new LinkedList();
        List registryProcessors =new LinkedList();

        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            if (postProcessorinstanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryProcessor =
                    (BeanDefinitionRegistryPostProcessor) postProcessor;
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
}
            else {
                regularPostProcessors.add(postProcessor);
}
}

    // Do not initialize FactoryBeans here: We need to leave all regular beans
    // uninitialized to let the bean factory post-processors apply to them!
    // Separate between BeanDefinitionRegistryPostProcessors that implement
    // PriorityOrdered, Ordered, and the rest.
List currentRegistryProcessors =new ArrayList();

// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
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);
            }
        }

    sortPostProcessors(currentRegistryProcessors, beanFactory);
    registryProcessors.addAll(currentRegistryProcessors);
// 执行BeanDefinitionRegistryPostProcessor类型的BeanPostProcessor, 继承了
// PriorityOrdered排序类型的, 函数postProcessBeanDefinitionRegistry
    invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
    currentRegistryProcessors.clear();

// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class,true,false);

    for (String ppName : postProcessorNames) {
    if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
        currentRegistryProcessors.add(beanFactory.getBean(ppName,         BeanDefinitionRegistryPostProcessor.class));
        processedBeans.add(ppName);
        }
    }

    sortPostProcessors(currentRegistryProcessors, beanFactory);
    registryProcessors.addAll(currentRegistryProcessors);
  // 执行BeanDefinitionRegistryPostProcessor类型的BeanPostProcessor, 继承了
   // Ordered排序类型的，函数postProcessBeanDefinitionRegistry
    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);
// 执行BeanDefinitionRegistryPostProcessor类型的BeanPostProcessor, 既没有继承
//Ordered，也没有继承PriorityOrdered。函数postProcessBeanDefinitionRegistry
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();
    }

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

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

    // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
    // Ordered, and the rest.
List priorityOrderedPostProcessors =new ArrayList();
    List orderedPostProcessorNames =new ArrayList();
    List nonOrderedPostProcessorNames =new ArrayList();
    for (String ppName : postProcessorNames) {
        if (processedBeans.contains(ppName)) {
            // skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName,             BeanFactoryPostProcessor.class));
        }
        else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
            orderedPostProcessorNames.add(ppName);
        }
        else {
            nonOrderedPostProcessorNames.add(ppName);
        }
    }

    // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List orderedPostProcessors =new ArrayList();
    for (String postProcessorName : orderedPostProcessorNames) {
        orderedPostProcessors.add(beanFactory.getBean(postProcessorName,         BeanFactoryPostProcessor.class));
    }

    sortPostProcessors(orderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
    // Finally, invoke all other BeanFactoryPostProcessors.

List nonOrderedPostProcessors =new ArrayList();
    for (String postProcessorName : nonOrderedPostProcessorNames) {
        nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName,         BeanFactoryPostProcessor.class));
    }

    invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
    // Clear cached merged bean definitions since the post-processors might have
    // modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}