Spring5源码 - PostProcessor后置处理器

谁借莪１个温暖的怀抱￠ 2022-09-07 14:39 74阅读 0赞

后置处理器大类分为容器级别的后置处理器以及Bean级别的后置处理器：

*  BeanDefinitionRegistryPostProcessor

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor { 
        void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
    }

允许在正常的BeanFactoryPostProcessor检测开始之前注册更多的自定义beandefinition。

例如，使用该后置BeanDefinitionRegistryPostProcessor注册一个bean。

public class User{ }
    
    @Configuration
    public class CustomizedBeanDefinitionPostProcessor implements BeanDefinitionRegistryPostProcessor { 
        @Override
        public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { 
    
        }
    
        @Override
        public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { 
            Class<User> clazz = User.class;
            BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(clazz);
            GenericBeanDefinition definition = (GenericBeanDefinition) builder.getRawBeanDefinition();
            registry.registerBeanDefinition("user5", definition);
        }
    }

*  BeanFactoryPostProcessor
    
    主要用于影响容器中的行为。

@FunctionalInterface
    public interface BeanFactoryPostProcessor { 
        void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
    }

*  BeanPostProcessor

Bean的后置处理器，其中包含两个回调方法，分别在Bean注册前和注册后调用。

@Configuration
    public class CustomizedBeanPostProcessor implements BeanPostProcessor { 
        @Override
        public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { 
            System.out.println(beanName + "注册前");
            return bean;
        }
    
        @Override
        public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { 
            System.out.println(beanName + "注册后");
            return bean;
        }
    }