Spring点滴十一：Spring中BeanFactoryPostProcessor和BeanPostProcessor区别

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。

关于BeanPostProcessor介绍在这篇文章中已经讲过：http://www.cnblogs.com/sishang/p/6576665.html这里主要介绍BeanFactoryPostProcessor。

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 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;  

    }

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

备注：下一篇将会介绍PropertyPlaceHoldConfigurer在Spring机制中如何读取配置文件的信息