Spring之后置处理器

 

Spring的后置处理器是Spring对外开发的重要扩展点，允许我们接入Bean的实例化流程中，以达到动态注册BeanDefinition、动态修改BeanDefinition、动态修改Bean的作用。

 

BeanFactoryPostProcessor

 

BeanFactory的后置处理器，在BeandefinitionMap填充完毕之后，Bean实例化之前执行。

BeanFactoryPostProcessor是一个接口规范，用于对BeanDefinition进行操作（注册、修改、删除）。

package org.springframework.beans.factory.config;  import org.springframework.beans.BeansException;  public interface BeanFactoryPostProcessor {     void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException; }

 

应用

• 方式一：自定义BeanFactoryPostProcessor接口实现类：实现BeanFactoryPostProcessor接口，并将实现类注册到Spring中，Spring就可以自动调用postProcessBeanFactory方法.

package com.blueStarWei.processor;  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.beans.factory.support.DefaultListableBeanFactory; import org.springframework.beans.factory.support.RootBeanDefinition; import org.springframework.stereotype.Component;  @Component public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {      public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {         // 注册         BeanDefinition definition = new RootBeanDefinition();         definition.setBeanClassName("com.blueStarWei.ObjectBeanFactory");         //必须强制转换为DefaultListableBeanFactory才能注册删除         DefaultListableBeanFactory defaultListableBeanFactory = (DefaultListableBeanFactory) beanFactory;         defaultListableBeanFactory.registerBeanDefinition("myBeanFactory",definition);          //删除         defaultListableBeanFactory.removeBeanDefinition("user");          //修改         BeanDefinition person = beanFactory.getBeanDefinition("person");         person.setScope(BeanDefinition.SCOPE_PROTOTYPE);     } }

• 方式二：自定义BeanDefinitionRegistryPostProcessor接口实现类：BeanDefinitionRegistryPostProcessor接口是BeanFactoryPostProcessor接口的子接口，主要用于注册BeanDefinition。【先调用postProcessBeanDefinitionRegistry(),再调用postProcessBeanFactory()】

package com.blueStarWei.processor;  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 MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {     public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {         System.out.println(">>>>>>>1. postProcessBeanDefinitionRegistry");         BeanDefinition definition = new RootBeanDefinition();         definition.setBeanClassName("com.blueStarWei.ObjectBeanFactory");         registry.registerBeanDefinition("myBeanFactory",definition);     }      public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {         System.out.println(">>>>>>>>>>2. postProcessBeanFactory");     } }

注意：当方式一与方式二同时使用时，调用顺序为：

• BeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry()
• BeanDefinitionRegistryPostProcessor.postProcessBeanFactory()
• BeanFactoryPostProcessor.postProcessBeanFactory()

 

BeanPostProcessor

Bean的后置处理器，一般在Bean的初始化前后执行。Bean实例化之后，填充到单例池singletonObjects之前执行，会进行Bean的初始化。

BeanPostProcessor是一个接口规范，用于对Bean进行修改。

package org.springframework.beans.factory.config;  import org.springframework.beans.BeansException;  public interface BeanPostProcessor {     /**     * 在Bean的初始化之前执行     */    Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;     /**     * 在Bean的初始化之后执行     */    Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;  }

 

应用

• 使用动态代理进行Bean的功能增强

package com.blueStarWei.processor;  import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanPostProcessor;  import java.lang.reflect.Proxy;  public class MyBeanPostProcessor implements BeanPostProcessor {     @Override     public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {         return bean;     }      /**      * 打印方法调用时间日志       * 注意：使用jdk自带的Proxy只能对有接口的类进行动态代理,直接代理POJO会报类型ClassCastException      *      */     @Override     public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {         Object beanProxy = Proxy.newProxyInstance(                 bean.getClass().getClassLoader(),                 bean.getClass().getInterfaces(),                 (proxy, method, args) -> {                     long startTime = System.currentTimeMillis();                     Object result = method.invoke(bean, args);                     long endTime = System.currentTimeMillis();                     System.out.println(beanName + "." + method.getName() + "执行时间：" + (endTime - startTime) + "ms.");                     return result;                 }         );         return beanProxy;     } }