Spring的后处理器

Spring的后处理器

源码

Spring 主要的两种后处理器

• BeanFactoryPostProcessor : Bean 工厂后处理器，在BeanDefinitionMap 填充完毕，Bean 实例化之前执行；
• BeanPostProcessor : Bean 后处理器，一般在 Bean 实例化之后，填充到单例池 SingletonObjects 之前执行；

BeanFactoryPostProcessor 向 BeanDefinitionMap 中进行注册、修改操作

xml 文件配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean class="com.kaiming.processor.MyBeanFactoryPostProcessor"></bean><bean id="userDao" class="com.kaiming.dao.impl.UserDaoImpl"></bean><!-- userService中注入userDao--><bean id="userService" class="com.kaiming.service.impl.UserServiceImpl"></bean>
</beans>    

注册

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("beanDefinitionMap填充完成后回调该方法");        // 注册RootBeanDefinition beanDefinition = new RootBeanDefinition();beanDefinition.setBeanClassName("com.kaiming.dao.impl.PersonDaoImpl");DefaultListableBeanFactory defaultListableBeanFactory = (DefaultListableBeanFactory) beanFactory;defaultListableBeanFactory.registerBeanDefinition("personDao", beanDefinition);}
}

test 获取 personDao

public class ApplicationContextTest {public static void main(String[] args) {BeanFactory beanFactory = new ClassPathXmlApplicationContext("beans.xml");Object personDao = beanFactory.getBean("personDao");System.out.println(personDao);}
}

beanDefinitionMap填充完成后回调该方法
com.kaiming.dao.impl.PersonDaoImpl@1e67a849

修改

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("beanDefinitionMap填充完成后回调该方法");BeanDefinition beanDefinition = beanFactory.getBeanDefinition("userService");beanDefinition.setBeanClassName("com.kaiming.dao.impl.UserDaoImpl");}
}

test

public class ApplicationContextTest {public static void main(String[] args) {BeanFactory beanFactory = new ClassPathXmlApplicationContext("beans.xml");      Object userService = beanFactory.getBean("userService");System.out.println(userService);}
}

beanDefinitionMap填充完成后回调该方法
com.kaiming.dao.impl.UserDaoImpl@448ff1a8

BeanFactoryPostProcessor 的子接口

源码

主要用于 BeanDefinition 注册

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry var1) throws BeansException;
}

一般注册 BeanDefinition 使用这个接口，不用针对 ConfigurableListableBeanFactory 进行强转

public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {@Overridepublic void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {RootBeanDefinition beanDefinition = new RootBeanDefinition();beanDefinition.setBeanClassName("com.kaiming.dao.impl.PersonDaoImpl");beanDefinitionRegistry.registerBeanDefinition("personDao", beanDefinition);}@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {}
}

xml 文件配置 MyBeanDefinitionRegistryPostProcessor

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean class="com.kaiming.processor.MyBeanFactoryPostProcessor"></bean><bean class="com.kaiming.processor.MyBeanDefinitionRegistryPostProcessor"></bean><bean id="userDao" class="com.kaiming.dao.impl.UserDaoImpl"></bean><!-- userService中注入userDao--><bean id="userService" class="com.kaiming.service.impl.UserServiceImpl"></bean></beans>     

test

public class ApplicationContextTest {public static void main(String[] args) {BeanFactory beanFactory = new ClassPathXmlApplicationContext("beans.xml");Object personDao = beanFactory.getBean("personDao");System.out.println(personDao);}
}

实现了 去实现 BeanFactoryPostProcessor 接口达到同样的效果

com.kaiming.dao.impl.PersonDaoImpl@41ee392b

关于实现了 BeanFactoryPostProcessor 和 BeanDefinitionRegistryPostProcessor 执行顺序

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {System.out.println("MyBeanFactoryPostProcessor的postProcessBeanFactory方法");}
}

public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {@Overridepublic void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {System.out.println("MyBeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法");RootBeanDefinition beanDefinition = new RootBeanDefinition();beanDefinition.setBeanClassName("com.kaiming.dao.impl.PersonDaoImpl");beanDefinitionRegistry.registerBeanDefinition("personDao", beanDefinition);}@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {System.out.println("MyBeanDefinitionRegistryPostProcessor的postProcessBeanFactory方法");}
}

MyBeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法
MyBeanDefinitionRegistryPostProcessor的postProcessBeanFactory方法
MyBeanFactoryPostProcessor的postProcessBeanFactory方法

BeanPostProcessor

Bean 被实例化后，到最终缓存到 SingletonObjects 单例池前，中间会经过 Bean 的初始化过程，例如：属性的填充，初始化 init 的执行等，其中有一个对外进行扩展的点 BeanPostProcessor ，称之为 Bean 后处理器。与 Bean 工厂后处理器相似，也是一个接口，实现了该接口并被容器管理的 BeanPostProcessor ,会在流程节点上被 Spring 自动调用。

// BeanPostProcessor 源码
public interface BeanPostProcessor {@Nullabledefault Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {return bean;}@Nullabledefault Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {return bean;}
}

创建一个 MyBeanPostProcessor 类实现 BeanPostProcessor 接口

public class MyBeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {System.out.println("postProcessBeforeInitialization");return bean;}@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {System.out.println("postProcessAfterInitialization");return bean;}
}

xml 文件配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean class="com.kaiming.processor.MyBeanPostProcessor"></bean><bean id="userDao" class="com.kaiming.dao.impl.UserDaoImpl"></bean></beans>     

test

public class ApplicationContextTest {public static void main(String[] args) {BeanFactory beanFactory = new ClassPathXmlApplicationContext("beans.xml");Object userDao = beanFactory.getBean("userDao");}
}

postProcessBeforeInitialization
postProcessAfterInitialization
com.kaiming.dao.impl.UserDaoImpl@3c0a50da

我们为 UserDaoImpl 添加无参构造器，init 方法，afterPropertiesSet 方法(实现 InitializingBean 接口)，观察执行顺序；

public class UserDaoImpl implements UserDao, InitializingBean {private String username;public void setName(String userName) {this.username = userName;}public UserDaoImpl() {System.out.println("userDao实例化");}public void init() {System.out.println("init初始化方法执行");}@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("属性设置之后执行");}
}

xml 文件配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean class="com.kaiming.processor.MyBeanPostProcessor"></bean><bean id="userDao" class="com.kaiming.dao.impl.UserDaoImpl" init-method="init"></bean></beans>     

test 测试

public class ApplicationContextTest {public static void main(String[] args) {BeanFactory beanFactory = new ClassPathXmlApplicationContext("beans.xml");Object userDao = beanFactory.getBean("userDao");System.out.println(userDao);}
}

userDao实例化
postProcessBeforeInitialization
属性设置之后执行
init初始化方法执行
postProcessAfterInitialization
com.kaiming.dao.impl.UserDaoImpl@797badd3

案例

对 Bean 方法进行执行时间日志增强

要求：

• Bean 的方法执行前控制台打印当前时间；
• Bean 的方法执行后控制台打印当前时间；

分析：

• 对方法进行增强主要采用代理和包装设计模式；
• 由于 Bean 方法不确定，所以使用动态代理在运行期间执行增强操作；
• 在 Bean 实例创建完成后，进入单例池前，使用 Proxy 代替真正的目标 Bean ;

TimeLogBeanPostProcessor 实现 BeanPostProcessor

public class TimeLogBeanPostProcessor implements BeanPostProcessor {@Overridepublic Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {// 使用动态代理对目标bean进行增强，返回Proxy对象，进而存储到SingletonObjects中Object beanProxy = Proxy.newProxyInstance(bean.getClass().getClassLoader(),bean.getClass().getInterfaces(),(proxy, method, args) -> {// 输出开始时间System.out.println("方法: " + method.getName() + "-开始时间: " + LocalDateTime.now());// 执行目标方法Object results = method.invoke(bean, args);// 输出结束时间System.out.println("方法: " + method.getName() + "-结束时间: " + LocalDateTime.now());return results;});return beanProxy;}
}

xml 文件配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean class="com.kaiming.processor.TimeLogBeanPostProcessor"></bean><bean id="userDao" class="com.kaiming.dao.impl.UserDaoImpl"></bean></beans>     

userDao 接口 抽象方法

public interface UserDao {    void show();
}

userDaoImpl 实现 userDao 接口

public class UserDaoImpl implements UserDao {@Overridepublic void show() {System.out.println("show()...");}
}

test 测试

public class ApplicationContextTest {public static void main(String[] args) {BeanFactory beanFactory = new ClassPathXmlApplicationContext("beans.xml");UserDao userDao = (UserDao) beanFactory.getBean("userDao");userDao.show();}
}

方法: show-开始时间: 2025-10-25T12:00:57.305161400
show()...
方法: show-结束时间: 2025-10-25T12:00:57.306161200