Spring注解系列二十七：BeanFactoryPostProcessor原理

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 beanFactoryPostProcessors) {
    Set processedBeans = new HashSet();
    int var9;
    ArrayList currentRegistryProcessors;
    String[] postProcessorNames;
    if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry)beanFactory;
        List regularPostProcessors = new LinkedList();
        List 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 priorityOrderedPostProcessors = new ArrayList();
    List 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 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 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 postProcessors, ConfigurableListableBeanFactory beanFactory) {
    Iterator var2 = postProcessors.iterator();

    while(var2.hasNext()) {
        BeanFactoryPostProcessor postProcessor = (BeanFactoryPostProcessor)var2.next();
        postProcessor.postProcessBeanFactory(beanFactory);
    }

}