Spring注解系列二十八：BeanDefinitionRegistryPostProcessor原理

本是古典何须时尚 2022-01-14 03:17 268阅读 0赞

一、BeanDefinitionRegistryPostProcessor 继承了 BeanFactoryPostProcessor 类。  
 postProcessBeanDefinitionRegistry()；  
 在所有bean定义信息将要被加载，bean实例还未创建的；优先于BeanFactoryPostProcessor执行；利用BeanDefinitionRegistryPostProcessor给容器中再额外添加一些组件。

自定义 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的数量："+beanFactory.getBeanDefinitionCount());
    	}
    
    	// BeanDefinitionRegistry Bean定义信息的保存中心，以后BeanFactory就是按照BeanDefinitionRegistry里面保存的每一个bean定义信息创建bean实例；
    	@Override
    	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
    		// TODO Auto-generated method stub
    		System.out.println("postProcessBeanDefinitionRegistry...bean的数量："+registry.getBeanDefinitionCount());
    		//RootBeanDefinition beanDefinition = new RootBeanDefinition(Blue.class);
    		AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.rootBeanDefinition(Blue.class).getBeanDefinition();
    		registry.registerBeanDefinition("hello", beanDefinition);
    	}
    
    }

测试：

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

控制台输出：

postProcessBeanDefinitionRegistry...bean的数量：11
    MyBeanDefinitionRegistryPostProcessor...bean的数量：12
    MyBeanFactoryPostProcessor...postProcessBeanFactory...
    当前BeanFactory中有12 个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 源码解析  
1、ioc创建对象；  
2、refresh() -》invokeBeanFactoryPostProcessors(beanFactory)；  
3、从容器中获取到所有的BeanDefinitionRegistryPostProcessor组件。  
（1）、依次触发所有的postProcessBeanDefinitionRegistry()方法；  
（2）、再来触发postProcessBeanFactory()方法BeanFactoryPostProcessor；  
4、再来从容器中找到BeanFactoryPostProcessor组件；然后依次触发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);
        }
    
    }