Spring注解系列二十七：BeanFactoryPostProcessor原理

太过爱你忘了你带给我的痛 2022-01-16 12:59 235阅读 0赞

BeanPostProcessor：bean后置处理器，bean创建对象初始化前后进行拦截工作的；  
一、BeanFactoryPostProcessor：beanFactory的后置处理器；在BeanFactory标准初始化之后调用，来定制和修改BeanFactory的内容；所有的bean定义已经保存加载到beanFactory，但是bean的实例还未创建。  
1、自定义的 BeanFactory 后置处理器 MyBeanFactoryPostProcessor

@Component
    public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    
    	@Override
    	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    		System.out.println("MyBeanFactoryPostProcessor...postProcessBeanFactory...");
    		int count = beanFactory.getBeanDefinitionCount();
    		String[] names = beanFactory.getBeanDefinitionNames();
    		System.out.println("当前BeanFactory中有"+count+" 个Bean");
    		System.out.println(Arrays.asList(names));
    	}
    
    }

2、Blue

public class Blue {
    	
    	public Blue(){
    		System.out.println("blue...constructor");
    	}
    	
    	public void init(){
    		System.out.println("blue...init...");
    	}
    	
    	public void detory(){
    		System.out.println("blue...detory...");
    	}
    
    }

3、配置类 ExtConfig

@ComponentScan("com.atguigu.ext")
    @Configuration
    public class ExtConfig {
    	
    	@Bean
    	public Blue blue(){
    		return new Blue();
    	}
    
    }

测试：

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

控制台输出：

MyBeanFactoryPostProcessor...postProcessBeanFactory...
    当前BeanFactory中有10 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, myBeanFactoryPostProcessor, userService, blue]
    blue...constructor

二、BeanFactoryPostProcessor源码解析:  
1、ioc容器创建对象；

public AnnotationConfigApplicationContext(Class... annotatedClasses) {
        this();
        this.register(annotatedClasses);
        this.refresh();
    }

public void refresh() throws BeansException, IllegalStateException {
            Object var1 = this.startupShutdownMonitor;
            synchronized(this.startupShutdownMonitor) {
                this.prepareRefresh();
                ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
                this.prepareBeanFactory(beanFactory);
    
                try {
                    this.postProcessBeanFactory(beanFactory);
                    this.invokeBeanFactoryPostProcessors(beanFactory);
                    this.registerBeanPostProcessors(beanFactory);
                    this.initMessageSource();
                    this.initApplicationEventMulticaster();
                    this.onRefresh();
                    this.registerListeners();
                    this.finishBeanFactoryInitialization(beanFactory);
                    this.finishRefresh();
                } catch (BeansException var9) {
                    if (this.logger.isWarnEnabled()) {
                        this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt: " + var9);
                    }
    
                    this.destroyBeans();
                    this.cancelRefresh(var9);
                    throw var9;
                } finally {
                    this.resetCommonCaches();
                }
    
            }
        }

2、invokeBeanFactoryPostProcessors(beanFactory);找到所有的BeanFactoryPostProcessor并执行他们的方法：  
（1）、直接在BeanFactory中找到所有类型是BeanFactoryPostProcessor的组件，并执行他们的方法；  
（2）、在初始化创建其他组件前面执行；

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
        PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, this.getBeanFactoryPostProcessors());
        if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean("loadTimeWeaver")) {
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }
    
    }

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 invokeBeanFactoryPostProcessors(Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {
        Iterator var2 = postProcessors.iterator();
    
        while(var2.hasNext()) {
            BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor)var2.next();
            postProcessor.postProcessBeanFactory(beanFactory);
        }
    
    }