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：