spring中的BeanFactoryPostProcessor

spring中的BeanFactoryPostProcessor和BeanPostProcessor有些像，BeanPostProcessor是在bean的初始化前后进行一些操作，

BeanFactoryPostProcessor是在所有的bean定义信息已经加载但还没有实例化时，执行方法postProcessBeanFactory（）

public interface BeanFactoryPostProcessor {

    /**
     * Modify the application context's internal bean factory after its standard
     * initialization. All bean definitions will have been loaded, but no beans
     * will have been instantiated yet. This allows for overriding or adding
     * properties even to eager-initializing beans.
     * @param beanFactory the bean factory used by the application context
     * @throws org.springframework.beans.BeansException in case of errors
     */
    void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;

}

我们自定义一个实现了BeanFactoryPostProcessor 的实现类MyBeanFactoryPostProcessor 

@Component

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("MyBeanFactoryPostProcessor >>>postProcessBeanFactory   ");
　　　　　　//获取已经加载的bean数
        int beanDefinitionCount = beanFactory.getBeanDefinitionCount();
　　　　　　//获取已经加载的bean名称
        String[] beanDefinitionNames = beanFactory.getBeanDefinitionNames();
        System.out.println("beanFactory中的bean数>>>"+beanDefinitionCount);
        System.out.println(Arrays.asList(beanDefinitionNames));
    }
}

配置类：

@Configuration
@Import({MyBeanFactoryPostProcessor.class})
public class ExtConfig {

    @Bean
    public Foo foo(){
        return new Foo();
    }
}

Foo类：

public class Foo {

    public Foo(){
        System.out.println("bean的创建");
    }


    @PostConstruct
    public void init(){
        System.out.println("bean的初始化");
    }

    @PreDestroy
    public void destroy(){
        System.out.println("bean的销毁");
    }
}

打印结果：

MyBeanFactoryPostProcessor >>>postProcessBeanFactory   
beanFactory中的bean数>>>8

[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, com.springExt.MyBeanFactoryPostProcessor]

bean的创建
bean的初始化

进行dubug也以看到：先执行BeanFactoryPostProcessors，后实例化非懒加载的bean

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

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                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.
                finishBeanFactoryInitialization(beanFactory);

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