Spring扩展接口-BeanDefinitionRegistryPostProcessor

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简介

在Spring容器初始化时，首先会读取应用程序中的配置文件，并解析出所有的Bean定义生成beanDefinition对象，并注册到容器中。
Spring提供了扩展接口BeanDefinitionRegistryPostProcessor，其中含有两个方法：

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {

    void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;

}

postProcessBeanDefinitionRegistry：入参是BeanDefinition注册器，允许用户自定义注册beanDefinition；
postProcessBeanFactory: 继承自BeanFactoryPostProcessor, 允许用户修改已经注册的beanDefinition。

用途示例

Spring内置处理器ConfigurationClassPostProcessor

处理spring定义的一些配置注解，例如@Configuration，@Import，@ComponentScan，@Bean等，并封装成BeanDefinition注册进容器中。

手动注册类示例

@Component

@Slf4j

public class MyBeanFactoryPostProcessor implements BeanDefinitionRegistryPostProcessor {

    @Override

    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {}

    /**

     * 动态注册Student的Bean信息

     *

     * @param registry

     * @throws BeansException

     */

    @Override

    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {

    BeanDefinition beanDefinition = BeanDefinitionBuilder.

                genericBeanDefinition(Student.class).

                addPropertyValue("id", "001").

                addPropertyValue("name", "tom001")

                .setInitMethodName("init")

                .setScope(BeanDefinition.SCOPE_SINGLETON)

                .getBeanDefinition();

        registry.registerBeanDefinition("student1", beanDefinition);

    }

}

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