目录
功能与作用
使用案例
spring提供的常见BeanFactoryPostProcessor
1.EventListenerMethodProcessor
2.BeanDefinitionRegistryPostProcessor
功能与作用
使用案例
spring提供的唯一BeanDefinitionRegistryPostProcessor
总结
功能与作用
参考BeanFactoryPostProcessor方法注释可知：该方法是在所有bean被加载，未被实例化前执行。对所有bean的属性可以修改也可以添加
@FunctionalInterface
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;
}使用案例
用户可以自定义一个实现BeanFactoryPostProcessor的类，获取某个bean修改bean的属性，比如如下举例修改该UserService类的属性由单例改为原型
@Component
public class UserService {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
package com.cyl.beanFactoryDemo;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.stereotype.Component;
@Component
public class CylBeanFactoryBeanPostProcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
BeanDefinition beanDefinition = beanFactory.getBeanDefinition("userService");
//修改该bean的属性为原型
beanDefinition.setScope("prototype");
//添加该bean的属性name默认值为cyl
MutablePropertyValues propertyValues = beanDefinition.getPropertyValues();
propertyValues.add("name","cyl");
}
}
spring提供的常见BeanFactoryPostProcessor
1.EventListenerMethodProcessor
处理添加了EventListener注解的逻辑，它的原理参见我的博文:
Spring注解@EventListener实现监听原理-CSDN博客文章浏览阅读903次，点赞21次，收藏14次。@EventListener实现原理主要通过EventListenerMethodProcessor和DefaultEventListenerFactory这两个类实现。EventListenerMethodProcessor的作用是识别所有使用eventListener注解的方法DefaultEventListenerFactory将EventListenerMethodProcessor识别出的方法封装成为监听器类以代码new AnnotationConfigApplicationContext为入https://blog.csdn.net/changyinling520/article/details/137205662?spm=1001.2014.3001.5502
2.BeanDefinitionRegistryPostProcessor
功能与作用
BeanDefinitionRegistryPostProcessor,该接口继承了BeanFactoryPostProcessor，拥有修改bean属性的功能，又拓展postProcessBeanDefinitionRegistry方法，通过代码注释理解:允许在bean被加载后，继续添加新的bean
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;
}postProcessBeanDefinitionRegistry方法先执行，postProcessBeanFactory后执行。
可以从详见：org.springframework.context.support.PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors(org.springframework.beans.factory.config.ConfigurableListableBeanFactory, java.util.List<org.springframework.beans.factory.config.BeanFactoryPostProcessor>)
使用案例
用户可以自定义一个实现BeanDefinitionRegistryPostProcessor的类，注册OrderService类到spring容器中，并修改它的属性值
1.创建一个不被spring管理的OrderService，内部有UserService属性
package com.cyl.beanFactoryDemo;
public class OrderService {
private UserService userService;
public UserService getUserService() {
return userService;
}
public void setUserService(UserService userService) {
this.userService = userService;
}
}
2.创建CylBeanRegistryPostProcessor实现了BeanDefinitionRegistryPostProcessor，在postProcessBeanDefinitionRegistry方法内注册OrderService类到容器中，在postProcessBeanFactory中给OrderService添加属性userService
package com.cyl.beanFactoryDemo;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.stereotype.Component;
@Component
public class CylBeanRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
RootBeanDefinition rootBeanDefinition = new RootBeanDefinition();
rootBeanDefinition.setBeanClass(OrderService.class);
registry.registerBeanDefinition("orderService", rootBeanDefinition);
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
BeanDefinition userServiceBean = beanFactory.getBeanDefinition("userService");
//修改该userService的属性name默认值为cyl
userServiceBean.getPropertyValues().addPropertyValue("name", "cyl");
BeanDefinition beanDefinition = beanFactory.getBeanDefinition("orderService");
//修改该orderService的添加属性userService
beanDefinition.getPropertyValues().add("userService", beanFactory.getBean(UserService.class));
}
}
最终输出结果
public static void main(String[] args) {
// 创建一个Spring容器
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
context.register(AppConfig.class);
context.refresh();
OrderService orderService = context.getBean(OrderService.class);
System.out.println(orderService.getUserService().getName());
}
spring提供的唯一BeanDefinitionRegistryPostProcessor
ConfigurationClassPostProcessor，这个类扫描所有component,service,import,configuration等注解，加载所有的bean定义到容器内。后续博文会详细介绍它的处理逻辑
总结
BeanFactoryProcessor是spring的一个拓展点，它的作用时机是在加载完所有的beanDefinition，还未实例化前。可以对beanDefinition进行加工，但是不可以加载beanDefinition。BeanDefinitionRegistryPostProcessor是BeanFactoryProcessor的子接口，增强了功能，既可以对beanDefinition加工，还可以加载自定义的beanDefinition。
