Spring註解系列二十八：BeanDefinitionRegistryPostProcessor原理

一、BeanDefinitionRegistryPostProcessor 繼承了 BeanFactoryPostProcessor 類。
 postProcessBeanDefinitionRegistry()；
 在所有bean定義信息將要被加載，bean實例還未創建的；優先於BeanFactoryPostProcessor執行；利用BeanDefinitionRegistryPostProcessor給容器中再額外添加一些組件。

自定義 BeanDefinitionRegistryPostProcessor

@Component
public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor{

	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
		// TODO Auto-generated method stub
		System.out.println("MyBeanDefinitionRegistryPostProcessor...bean的數量："+beanFactory.getBeanDefinitionCount());
	}

	// BeanDefinitionRegistry Bean定義信息的保存中心，以後BeanFactory就是按照BeanDefinitionRegistry裏面保存的每一個bean定義信息創建bean實例；
	@Override
	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
		// TODO Auto-generated method stub
		System.out.println("postProcessBeanDefinitionRegistry...bean的數量："+registry.getBeanDefinitionCount());
		//RootBeanDefinition beanDefinition = new RootBeanDefinition(Blue.class);
		AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.rootBeanDefinition(Blue.class).getBeanDefinition();
		registry.registerBeanDefinition("hello", beanDefinition);
	}

}

測試：

@Test
public void test01(){
	AnnotationConfigApplicationContext applicationContext  = new AnnotationConfigApplicationContext(ExtConfig.class);
	
	applicationContext.close();
}

控制檯輸出：

postProcessBeanDefinitionRegistry...bean的數量：11
MyBeanDefinitionRegistryPostProcessor...bean的數量：12
MyBeanFactoryPostProcessor...postProcessBeanFactory...
當前BeanFactory中有12 個Bean
[org.springframework.context.annotation.internalConfigurationAnnotationProcessor, org.springframework.context.annotation.internalAutowiredAnnotationProcessor, org.springframework.context.annotation.internalRequiredAnnotationProcessor, org.springframework.context.annotation.internalCommonAnnotationProcessor, org.springframework.context.event.internalEventListenerProcessor, org.springframework.context.event.internalEventListenerFactory, extConfig, myBeanDefinitionRegistryPostProcessor, myBeanFactoryPostProcessor, userService, blue, hello]
blue...constructor
blue...constructor

二、BeanDefinitionRegistryPostProcessor 源碼解析
1、ioc創建對象；
2、refresh() -》invokeBeanFactoryPostProcessors(beanFactory)；
3、從容器中獲取到所有的BeanDefinitionRegistryPostProcessor組件。
（1）、依次觸發所有的postProcessBeanDefinitionRegistry()方法；
（2）、再來觸發postProcessBeanFactory()方法BeanFactoryPostProcessor；
4、再來從容器中找到BeanFactoryPostProcessor組件；然後依次觸發postProcessBeanFactory()方法。

public static void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
    Set<String> processedBeans = new HashSet();
    int var9;
    ArrayList currentRegistryProcessors;
    String[] postProcessorNames;
    if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry)beanFactory;
        List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList();
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList();
        Iterator var6 = beanFactoryPostProcessors.iterator();

        while(var6.hasNext()) {
            BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor)var6.next();
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor)postProcessor;
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            } else {
                regularPostProcessors.add(postProcessor);
            }
        }

        currentRegistryProcessors = new ArrayList();
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        String[] var18 = postProcessorNames;
        var9 = postProcessorNames.length;

        int var10;
        String ppName;
        for(var10 = 0; var10 < var9; ++var10) {
            ppName = var18[var10];
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }

        sortPostProcessors(currentRegistryProcessors, beanFactory);
        registryProcessors.addAll(currentRegistryProcessors);
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        var18 = postProcessorNames;
        var9 = postProcessorNames.length;

        for(var10 = 0; var10 < var9; ++var10) {
            ppName = var18[var10];
            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);
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
        currentRegistryProcessors.clear();
        boolean reiterate = true;

        while(reiterate) {
            reiterate = false;
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            String[] var21 = postProcessorNames;
            var10 = postProcessorNames.length;

            for(int var28 = 0; var28 < var10; ++var28) {
                String ppName = var21[var28];
                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();
        }

        invokeBeanFactoryPostProcessors((Collection)registryProcessors, (ConfigurableListableBeanFactory)beanFactory);
        invokeBeanFactoryPostProcessors((Collection)regularPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
    } else {
        invokeBeanFactoryPostProcessors((Collection)beanFactoryPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
    }

    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
    List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList();
    List<String> orderedPostProcessorNames = new ArrayList();
    currentRegistryProcessors = new ArrayList();
    postProcessorNames = postProcessorNames;
    int var22 = postProcessorNames.length;

    String ppName;
    for(var9 = 0; var9 < var22; ++var9) {
        ppName = postProcessorNames[var9];
        if (!processedBeans.contains(ppName)) {
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
                orderedPostProcessorNames.add(ppName);
            } else {
                currentRegistryProcessors.add(ppName);
            }
        }
    }

    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors((Collection)priorityOrderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
    List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList();
    Iterator var23 = orderedPostProcessorNames.iterator();

    while(var23.hasNext()) {
        String postProcessorName = (String)var23.next();
        orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
    }

    sortPostProcessors(orderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors((Collection)orderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
    List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList();
    Iterator var26 = currentRegistryProcessors.iterator();

    while(var26.hasNext()) {
        ppName = (String)var26.next();
        nonOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
    }

    invokeBeanFactoryPostProcessors((Collection)nonOrderedPostProcessors, (ConfigurableListableBeanFactory)beanFactory);
    beanFactory.clearMetadataCache();
}

private static void invokeBeanDefinitionRegistryPostProcessors(Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
    Iterator var2 = postProcessors.iterator();

    while(var2.hasNext()) {
        BeanDefinitionRegistryPostProcessor postProcessor = (BeanDefinitionRegistryPostProcessor)var2.next();
        postProcessor.postProcessBeanDefinitionRegistry(registry);
    }

}