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
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsd"> class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" /> class="com.test.spring.PostProcessor"/> class="com.test.spring.FactoryPostProcessor"/> class="com.test.spring.BeanFactoryPostProcessorTest">
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{@Overridepublic 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;}@Overridepublic 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 {@Overridepublic 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;}@Overridepublic void setBeanFactory(BeanFactory paramBeanFactory)throws BeansException {System.out.println("》》》调用了BeanFactoryAware的setBeanFactory方法了");}@Overridepublic void setBeanName(String paramString) {System.out.println("》》》调用了BeanNameAware的setBeanName方法了");}@Overridepublic void destroy() throws Exception {System.out.println("》》》调用了DisposableBean的destroy方法了"); }@Overridepublic void afterPropertiesSet() throws Exception {System.out.println("》》》调用了Initailization的afterPropertiesSet方法了");}@Overridepublic 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;@Beforepublic 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......");}@Testpublic 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]
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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。
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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
