spring 后置处理器BeanFactoryPostProcessor和BeanPostProcessor的用法和区别

 

主要区别就是： BeanFactoryPostProcessor可以修改BEAN的配置信息而BeanPostProcessor不能，下面举个例子说明

BEAN类：

package com.springdemo.postProcessor;

public class PostProcessorBean {
    private String username;

    private String password;

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }
}

MyBeanPostProcessor类，实现了BeanPostProcessor接口:

package com.springdemo.postProcessor;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

import com.springdemo.form.LoginForm;

public class MyBeanPostProcessor implements BeanPostProcessor {



    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
        // TODO Auto-generated method stub
        //如果是PostProcessorBean则username信息
        if(bean instanceof PostProcessorBean)
        {
            System.out.println("PostProcessorBean Bean initialized");
            PostProcessorBean pb = (PostProcessorBean)bean;

            System.out.println("username:"+pb.getUsername());
        }
        return bean;
    }

    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        // TODO Auto-generated method stub
        if(bean instanceof PostProcessorBean)
        {
            System.out.println("PostProcessorBean Bean initializing");
            PostProcessorBean pb = (PostProcessorBean)bean;

            System.out.println("username:"+pb.getUsername());
        }
        return bean;
    }

}

MyBeanFactoryPostProcessor实现了BeanFactoryPostProcessor接口:

package com.springdemo.postProcessor;

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

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {

    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
            throws BeansException {
        // TODO Auto-generated method stub
        //BeanFactoryPostProcessor可以修改BEAN的配置信息而BeanPostProcessor不能
        //我们在这里修改postProcessorBean的username注入属性
        BeanDefinition bd = beanFactory.getBeanDefinition("postProcessorBean");
        MutablePropertyValues pv =  bd.getPropertyValues();
        if(pv.contains("username"))
        {
            pv.addPropertyValue("username", "xiaojun");
        }

    }

}

编写测试用例：

package com.springdemo.test;


import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.springdemo.factory.ApplicationContextFactory;

import com.springdemo.postProcessor.PostProcessorBean;

import junit.framework.TestCase;

public class BeanPostPorcessorTest extends TestCase {
    private ApplicationContext context;
    protected void setUp() throws Exception {
        super.setUp();
        String[] paths = {"classpath*:/spring/applicationContext-*.xml"};

        context = new ClassPathXmlApplicationContext(paths);

    }

    protected void tearDown() throws Exception {
        super.tearDown();
    }

    public void testBeanPostProcessor()
    {

    }
    public void testBeanFactoryPostProcessor()
    {
        //PostProcessorBean bean =(PostProcessorBean)ServiceLocator.getService("postProcessorBean");
        PostProcessorBean bean =(PostProcessorBean)context.getBean("postProcessorBean");
        System.out.println("---------------testBeanFactoryPostProcessor----------------");
        System.out.println("username:"+bean.getUsername());
        System.out.println("password:"+bean.getPassword());
        //
    }
}

spring配置文件如下（先不启用MyBeanFactoryPostProcessor）：

<?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-2.0.xsd">

    <bean class="com.springdemo.postProcessor.MyBeanPostProcessor"></bean>
    <!--我们先把BeanFactoryPostProcessor注释掉，不启用,然后查看测试输出结果
    <bean class="com.springdemo.postProcessor.MyBeanFactoryPostProcessor"></bean>
    -->
    <bean id="postProcessorBean" class="com.springdemo.postProcessor.PostProcessorBean" >
        <property name="username" value="test"></property>
        <property name="password" value="test"></property>
    </bean>
</beans>

测试输出结果如下：

PostProcessorBean Bean initializing
username:test
PostProcessorBean Bean initialized
username:test
---------------testBeanFactoryPostProcessor----------------
username:test
password:test

然后我们取消注释启用MyBeanFactoryPostProcessor，测试结果如下：

PostProcessorBean Bean initializing
username:xiaojun
PostProcessorBean Bean initialized
username:xiaojun
---------------testBeanFactoryPostProcessor----------------
username:xiaojun
password:test

从结果可以看出：BeanFactoryPostProcessor的回调比BeanPostProcessor要早，因为 BeanPostProcess中输出的username已经变成了xiaojun,而不是test.还有就是 BeanFactoryPostProcessor确实有能力改变初始化BEAN的内容，您可以试试在MyBeanPostProcess中试一试set 一下username看看能不能改变BEAN实例的内容(答案应该是否定的).

原文：

spring 后置处理器BeanFactoryPostProcessor和BeanPostProcessor的用法和区别