Spring中BeanFactoryPostProcessor的详解

Posted 2022-06-13 deityjian

  Spring中BeanFactoryPostProcessor和BeanPostProcessor都是Spring初始化bean时对外暴露的扩展点。两个接口从名字看起来很相似，但是作用及使用场景却不同。

   Spring IoC容器允许BeanFactoryPostProcessor在容器实例化任何bean之前读取bean的定义(配置元数据)，并可以修改它。同时可以定义多个BeanFactoryPostProcessor，通过设置‘order‘属性来确定各个BeanFactoryPostProcessor执行顺序。

   注册一个BeanFactoryPostProcessor实例需要定义一个Java类来实现BeanFactoryPostProcessor接口，并重写该接口的postProcessorBeanFactory方法。通过beanFactory可以获取bean的定义信息，并可以修改bean的定义信息。这点是和BeanPostProcessor最大区别

public interfac BeanFactoryPostProcessor   
      
        void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;  
      
    

spring.xml

<?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">
    <!-- 支持Spring注解 -->
    <bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" />
    <!-- 注册一个BeanPostProcessor -->
    <bean id="postProcessor" class="com.test.spring.PostProcessor"/>
    <!-- 注册一个BeanFactoryPostProcessor -->
    <bean id="factoryPostProcessor" class="com.test.spring.FactoryPostProcessor"/>
    <!-- 普通bean -->
    <bean id="beanFactoryPostProcessorTest" class="com.test.spring.BeanFactoryPostProcessorTest">
           <property name="name" value="张三"/>
           <property name="sex" value="男"/>
     </bean>
</beans>

BeanPostProcessor.java

package com.test.spring;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
/**
 * bean后置处理器
 * @author zss
 *
 */
public class PostProcessor implements BeanPostProcessor

    @Override
    public Object postProcessBeforeInitialization(Object bean,
            String beanName) throws BeansException 
        System.out.println("后置处理器处理bean=【"+beanName+"】开始");
        try 
            Thread.sleep(1000);
         catch (InterruptedException e) 
            e.printStackTrace();
        
        return bean;
    

    @Override
    public Object postProcessAfterInitialization(Object bean,
            String beanName) throws BeansException 
        System.out.println("后置处理器处理bean=【"+beanName+"】完毕!");
        try 
            Thread.sleep(1000);
         catch (InterruptedException e) 
            e.printStackTrace();
        
        return bean;
    

BeanFactoryPostProcessor.java

package com.test.spring;

import org.springframework.beans.BeansException;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

public class FactoryPostProcessor implements BeanFactoryPostProcessor 

    @Override
    public void postProcessBeanFactory(
            ConfigurableListableBeanFactory configurableListableBeanFactory)
            throws BeansException 
        System.out.println("******调用了BeanFactoryPostProcessor");
        String[] beanStr = configurableListableBeanFactory
                .getBeanDefinitionNames();
        for (String beanName : beanStr) 
            if ("beanFactoryPostProcessorTest".equals(beanName)) 
                BeanDefinition beanDefinition = configurableListableBeanFactory
                        .getBeanDefinition(beanName);
                MutablePropertyValues m = beanDefinition.getPropertyValues();
                if (m.contains("name")) 
                    m.addPropertyValue("name", "赵四");
                    System.out.println("》》》修改了name属性初始值了");
                
            
        
    

BeanFactoryPostProcessorTest.java

package com.test.spring;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

public class BeanFactoryPostProcessorTest implements InitializingBean,DisposableBean,BeanNameAware,BeanFactoryAware 
    private String name;
    private String sex;

    public String getName() 
        return name;
    

    public void setName(String name) 
        this.name = name;
    

    public String getSex() 
        return sex;
    

    public void setSex(String sex) 
        this.sex = sex;
    

    @Override
    public void setBeanFactory(BeanFactory paramBeanFactory)
            throws BeansException 
        System.out.println("》》》调用了BeanFactoryAware的setBeanFactory方法了");
    

    @Override
    public void setBeanName(String paramString) 
        System.out.println("》》》调用了BeanNameAware的setBeanName方法了");
    

    @Override
    public void destroy() throws Exception 
        System.out.println("》》》调用了DisposableBean的destroy方法了");        
    

    @Override
    public void afterPropertiesSet() throws Exception 
        System.out.println("》》》调用了Initailization的afterPropertiesSet方法了");
    

    @Override
    public String toString() 
        return "BeanFactoryPostProcessorTest [name=" + name + ", sex=" + sex
                + "]";
    

Test case:

package com.test.spring;

import org.junit.Before;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class T 
    ApplicationContext applicationcontext=null;
    @Before
    public void before() 
        System.out.println("》》》Spring ApplicationContext容器开始初始化了......");
        applicationcontext= new ClassPathXmlApplicationContext(new String[]"spring-service.xml");
        System.out.println("》》》Spring ApplicationContext容器初始化完毕了......");
    
    @Test
    public void  test() 
        //BeanLifecycle beanLifecycle =applicationcontext.getBean("beanLifecycle",BeanLifecycle.class);
        BeanFactoryPostProcessorTest beanFactoryPostProcessorTest=applicationcontext.getBean(BeanFactoryPostProcessorTest.class);
        System.out.println(beanFactoryPostProcessorTest.toString());
    

测试结果：

》》》Spring ApplicationContext容器开始初始化了......
2017-03-20 14:36:10  INFO:ClassPathXmlApplicationContext-Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@17ad352e: startup date [Mon Mar 20 14:36:10 CST 2017]; root of context hierarchy
2017-03-20 14:36:10  INFO:XmlBeanDefinitionReader-Loading XML bean definitions from class path resource [spring-service.xml]
******调用了BeanFactoryPostProcessor
》》》修改了name属性初始值了
》》》调用了BeanNameAware的setBeanName方法了
》》》调用了BeanFactoryAware的setBeanFactory方法了
后置处理器处理bean=【beanFactoryPostProcessorTest】开始
后置处理器开始调用了
》》》调用了Initailization的afterPropertiesSet方法了
后置处理器处理bean=【beanFactoryPostProcessorTest】完毕!
后置处理器调用结束了
》》》Spring ApplicationContext容器初始化完毕了......
BeanFactoryPostProcessorTest [name=赵四, sex=男]

从测试结果中可以看到beanFactoryPostProcessorTest定义的name值由"张三"变为"赵四"，同时发现postProcessorBeanFactory方法执行顺序先于BeanPostProcessor接口中方法。

  在Spring中内置了一些BeanFactoryPostProcessor实现类：

• org.springframework.beans.factory.config.PropertyPlaceholderConfigurer
• org.springframework.beans.factory.config.PropertyOverrideConfigurer
• org.springframework.beans.factory.config.CustomEditorConfigurer：用来注册自定义的属性编辑器