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：

1. package com.springdemo.postProcessor;
2. public class PostProcessorBean {
3. private String username;
4. private String password;
5. public String getPassword() {
6. return password;
7. }
8. public void setPassword(String password) {
9. this.password = password;
10. }
11. public String getUsername() {
12. return username;
13. }
14. public void setUsername(String username) {
15. this.username = username;
16. }
17. }

MyBeanPostProcessor类，实现了BeanPostProcessor接口:

1. package com.springdemo.postProcessor;
2. import org.springframework.beans.BeansException;
3. import org.springframework.beans.factory.config.BeanPostProcessor;
4. import com.springdemo.form.LoginForm;
5. public class MyBeanPostProcessor implements BeanPostProcessor {
6. public Object postProcessAfterInitialization(Object bean, String beanName)
7. throws BeansException {
8. // TODO Auto-generated method stub
9. //如果是PostProcessorBean则username信息
10. if(bean instanceof PostProcessorBean)
11. {
12. System.out.println("PostProcessorBean Bean initialized");
13. PostProcessorBean pb = (PostProcessorBean)bean;
14. System.out.println("username:"+pb.getUsername());
15. }
16. return bean;
17. }
18. public Object postProcessBeforeInitialization(Object bean, String beanName)
19. throws BeansException {
20. // TODO Auto-generated method stub
21. if(bean instanceof PostProcessorBean)
22. {
23. System.out.println("PostProcessorBean Bean initializing");
24. PostProcessorBean pb = (PostProcessorBean)bean;
25. System.out.println("username:"+pb.getUsername());
26. }
27. return bean;
28. }
29. }

MyBeanFactoryPostProcessor实现了BeanFactoryPostProcessor接口:

1. package com.springdemo.postProcessor;
2. import org.springframework.beans.BeansException;
3. import org.springframework.beans.MutablePropertyValues;
4. import org.springframework.beans.factory.config.BeanDefinition;
5. import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
6. import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
7. public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
8. public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
9. throws BeansException {
10. // TODO Auto-generated method stub
11. //BeanFactoryPostProcessor可以修改BEAN的配置信息而BeanPostProcessor不能
12. //我们在这里修改postProcessorBean的username注入属性
13. BeanDefinition bd = beanFactory.getBeanDefinition("postProcessorBean");
14. MutablePropertyValues pv =  bd.getPropertyValues();
15. if(pv.contains("username"))
16. {
17. pv.addPropertyValue("username", "xiaojun");
18. }
19. }
20. }

编写测试用例：

1. package com.springdemo.test;
2. import org.springframework.context.ApplicationContext;
3. import org.springframework.context.support.ClassPathXmlApplicationContext;
4. import com.springdemo.factory.ApplicationContextFactory;
5. import com.springdemo.postProcessor.PostProcessorBean;
6. import junit.framework.TestCase;
7. public class BeanPostPorcessorTest extends TestCase {
8. private ApplicationContext context;
9. protected void setUp() throws Exception {
10. super.setUp();
11. String[] paths = {"classpath*:/spring/applicationContext-*.xml"};
12. context = new ClassPathXmlApplicationContext(paths);
13. }
14. protected void tearDown() throws Exception {
15. super.tearDown();
16. }
17. public void testBeanPostProcessor()
18. {
19. }
20. public void testBeanFactoryPostProcessor()
21. {
22. //PostProcessorBean bean =(PostProcessorBean)ServiceLocator.getService("postProcessorBean");
23. PostProcessorBean bean =(PostProcessorBean)context.getBean("postProcessorBean");
24. System.out.println("---------------testBeanFactoryPostProcessor----------------");
25. System.out.println("username:"+bean.getUsername());
26. System.out.println("password:"+bean.getPassword());
27. //
28. }
29. }

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

1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
5. <bean class="com.springdemo.postProcessor.MyBeanPostProcessor"></bean>
6. <!--我们先把BeanFactoryPostProcessor注释掉，不启用,然后查看测试输出结果
7. <bean class="com.springdemo.postProcessor.MyBeanFactoryPostProcessor"></bean>
8. -->
9. <bean id="postProcessorBean" class="com.springdemo.postProcessor.PostProcessorBean" >
10. <property name="username" value="test"></property>
11. <property name="password" value="test"></property>
12. </bean>
13. </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