BeanDefinitionRegistryPostProcessor的作用

https://cloud.tencent.com/developer/article/1359672

最近在看spring集成mybatis的代码,发现MapperScannerConfigurer实现了BeanDefinitionRegistryPostProcessor接口:

很好奇BeanDefinitionRegistryPostProcessor有什么作用呢,看看MapperScannerConfigurer中postProcessBeanDefinitionRegistry方法的调用关系:

原来是在 org.springframework.context.support.AbstractApplicationContext#refresh方法中调用的:

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

该方法是让我们自定义的注册bean,下面来实现自定义bean并注册到BeanDefinitionRegistry:

/**
 * @author LiosWong
 * @description
 * @date 2018/9/5 下午10:14
 */
@Component
public class TestPostProcessorRegistration implements BeanDefinitionRegistryPostProcessor{
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        //创建BeanDefinitionBuilder
        BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(UserInfoEntity.class);
        //设置属性值
        builder.addPropertyValue("name","list_test");
        //设置可通过@Autowire注解引用
        builder.setAutowireMode(AUTOWIRE_BY_NAME
        //注册到BeanDefinitionRegistry
        registry.registerBeanDefinition("userInfoEntity",builder.getBeanDefinition());
    }
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

    }
}

Test:

@RestController
public class OkController {
    @Autowired
    UserInfoEntity userInfoEntity;
    @GetMapping(value = "/ok")
    public String  ok(){
        return userInfoEntity.getName();
    }

返回的是lios_test,至此完成了自定义bean并成功使用了。