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).