BeanFactoryPostProcessor

BeanFactoryPostProcessor:beanFactory 的后置处理器
beanFactory 标准初始化之后调用；所有bean已经保存到beanFactory，但是bean 实例还未创建
编写一个MyBeanFactoryPostProcessor测试类

@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("=======================MyBeanFactoryPostProcessor");
        int count = beanFactory.getBeanDefinitionCount();
        String[] names = beanFactory.getBeanDefinitionNames();
        System.out.println("当前beanfactory有"+count+"个bean");
        Arrays.asList(names).stream().forEach(System.out::println);

    }
}

配置类

@Configuration
@ComponentScan("com.funtl.hello.spring.cloud.eureka.postprocessor")
public class ExtConfig {
}

测试类

public class TestSpringExt {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(ExtConfig.class);
        applicationContext.close();
    }
}

启动容器控制台打印如下

=======================MyBeanFactoryPostProcessor
当前beanfactory有11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
cat
dog
myBeanFactoryPostProcessor
myBeanPostProcessor

上面的11 个bean都只是bean定义信息并没有创建对象实例。我们在MyBeanFactoryPostProcessor的postProcessBeanFactory方法打个断点

图1

图2

public static void invokeBeanFactoryPostProcessors(
            ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors)
//这里就是获得所有BeanFactoryPostProcessor 类型的bean名称（编译的时候已经将所有类信息放到常量池中，所以只要编译就会有类信息，但是并灭有创建对象）
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); 
        for (String postProcessorName : nonOrderedPostProcessorNames) {
//getBean 方法就是 根据class 信息通过反射创建bean 实例，其中又会经过一系列的前置后置方法初始化方法等。
            nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
        }
        invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory); 
    }

进入invokeBeanFactoryPostProcessors()方法我们就会发现很简单这里就是调用 所有BeanFactoryPostProcessor 的postProcessBeanFactory（）方法

private static void invokeBeanFactoryPostProcessors(
            Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {

        for (BeanFactoryPostProcessor postProcessor : postProcessors) {
            postProcessor.postProcessBeanFactory(beanFactory);
        }
    }

@Override
    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                                //这里是创建BeanFactoryPostProcessors 对象
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                                //这里是创建 BeanPostProcessors 对象
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                initMessageSource();

                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // Check for listener beans and register them.
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                                //这里才是执行剩下的所有bean 创建bean 实例对象
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                finishRefresh();
            }
 
        }
    }

整个过程

1. ioc容器创建对象
2. invokeBeanFactoryPostProcessors(beanFactory);
   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. 在执行初始化创建其他组件前面执行

BeanDefinitionRegistryPostProcessor

BeanDefinitionRegistryPostProcessor 继承了 BeanFactoryPostProcessor接口，并且增加了一个postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)方法。
在所有bean 定义信息将要加载，bean实例还未创建；优先于BeanFactoryPostProcessor执行
利用BeanDefinitionRegistryPostProcessor给容器中额外添加组件

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {

    /**
     * Modify the application context's internal bean definition registry after its
     * standard initialization. All regular bean definitions will have been loaded,
     * but no beans will have been instantiated yet. This allows for adding further
     * bean definitions before the next post-processing phase kicks in.
     * @param registry the bean definition registry used by the application context
     * @throws org.springframework.beans.BeansException in case of errors
     */
    void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;

}

创建一个MyBeanDefinitionRegistryPostProcessor

@Component
public class MyBeanDefinitionRegistryPostProcessor  implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        System.out.println("postProcessBeanDefinitionRegistry++++++++bean的数量" +registry.getBeanDefinitionCount());
       // RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(Person.class);
        AbstractBeanDefinition rootBeanDefinition = BeanDefinitionBuilder.rootBeanDefinition(Person.class).getBeanDefinition();
        registry.registerBeanDefinition("person",rootBeanDefinition);
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("postProcessBeanFactory++++++++bean的数量" +beanFactory.getBeanDefinitionCount());
    }
}

控制台输出

postProcessBeanDefinitionRegistry++++++++bean的数量12
postProcessBeanFactory++++++++bean的数量13

分析一下先执行postProcessBeanDefinitionRegistry()方法 现在有12 个bean定义信息，再执行postProcessBeanFactory有13个bean 定义信息加了一个person
在MyBeanDefinitionRegistryPostProcessor 打一个断点

image.png

image.png

public static void invokeBeanFactoryPostProcessors(
            ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
                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);
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                currentRegistryProcessors.clear();
    }

    private static void invokeBeanDefinitionRegistryPostProcessors(
            Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {

        for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
            postProcessor.postProcessBeanDefinitionRegistry(registry);
        }
    }

这段伪代码在上面那段伪代码之前执行，所以这也就解释了为什么先执行postProcessBeanDefinitionRegistry再执行postProcessBeanFactory

过程

1. ioc 创建对象
2. refresh()->invokeBeanFactoryPostProcessor(beanFactory);
3. 从容器中获取到所有BeanDefinitionRegistryPostProcessor组件
   1. 依次触发所有postProcessorBeanDefinitionRegistry（）方法
   2. 再来触发postProcessorBeanFactory（）方法