Spring Bean 初始化历程

Spring Bean 初始化过程

转：http://blog.csdn.net/zhjb1025/article/details/3244728

Spring 的几个接口

1.InitializingBean接口，在初始化Bean时容器会调用前者的afterPropertiesSet()方法

2.DisposableBean接口，在析构Bean时容器会调用destroy()方法，在下面的例子中好像没有体现出来（革命尚未成功，同志仍需努力）

3.BeanFactoryAware接口，当它被BeanFactory创建后，它会拥有一个指向创建它的BeanFactory的引用

4.BeanPostProcessor接口，这个接口两个方法，postProcessBeforeInitialization(Object bean, String beanName)和postProcessAfterInitialization(Object bean, String beanName) 在其他Bean构造前后执行

5.BeanFactoryPostProcessor接口，Spring IoC容器允许BeanFactoryPostProcessor在容器实际实例化任何其它的bean之前读取配置元数据，并有可能修改它

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下面来看一下例子

package?com.test;
1. public?class?User?{
2. ????private?String?name;????
3. ????public?String?getName()?{????????return?name;
4. ????}
5. ????public?void?setName(String?name)?{????????System.out.println("User类?setName方法");
6. ????????this.name?=?name;????}
7. ????public?void?init()?throws?Exception?{????????System.out.println("User类init?方法");
8. ????????????}
9. ????public?User(){????????System.out.println("User类构造方法");
10. ????}????
11. }

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package?com.test;
1. import?org.springframework.beans.BeansException;
2. import?org.springframework.beans.factory.BeanFactory;import?org.springframework.beans.factory.BeanFactoryAware;
3. import?org.springframework.beans.factory.DisposableBean;import?org.springframework.beans.factory.InitializingBean;
4. import?org.springframework.beans.factory.config.BeanFactoryPostProcessor;import?org.springframework.beans.factory.config.BeanPostProcessor;
5. import?org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
6. public?class?JavaBean?implements?InitializingBean,DisposableBean,BeanFactoryAware,BeanPostProcessor?,BeanFactoryPostProcessor{????private?String?name;
7. ????public?JavaBean(){????????System.out.println("JavaBean类构造方法");
8. ????}????@Override
9. ????public?void?afterPropertiesSet()?throws?Exception?{????????System.out.println("InitializingBean?接口?afterPropertiesSet方法");
10. ????????????}
11. ????@Override
12. ????public?void?destroy()?throws?Exception?{????????System.out.println("DisposableBean?接口?destroy方法");
13. ????????????}
14. ????public?void?init()?throws?Exception?{????????System.out.println("JavaBean类init?方法");
15. ????????????}
16. ????@Override
17. ????public?void?setBeanFactory(BeanFactory?beanFactory)?throws?BeansException?{????????System.out.println("BeanFactoryAware?接口?setBeanFactory方法");
18. ????????????}
19. ????@Override
20. ????public?Object?postProcessAfterInitialization(Object?bean,?String?beanName)????????????throws?BeansException?{
21. ????????System.out.println(beanName+":BeanPostProcessor?接口?postProcessAfterInitialization方法");????????return?bean;
22. ????}
23. ????@Override????public?Object?postProcessBeforeInitialization(Object?bean,?String?beanName)
24. ????????????throws?BeansException?{????????System.out.println(beanName+":BeanPostProcessor?接口?postProcessBeforeInitialization?方法");
25. ????????return?bean;????}
26. ????public?String?getName()?{
27. ????????return?name;????}
28. ????public?void?setName(String?name)?{
29. ????????System.out.println("JavaBean类setName?方法");????????this.name?=?name;
30. ????}????@Override
31. ????public?void?postProcessBeanFactory(????????????ConfigurableListableBeanFactory?beanFactory)?throws?BeansException?{
32. ????????System.out.println("BeanFactoryPostProcessor?接口?postProcessBeanFactory?方法");????}
33. ????
34. }

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package?com.test;
1. import?org.springframework.context.ApplicationContext;
2. import?org.springframework.context.support.ClassPathXmlApplicationContext;
3. public?class?Test?{
4. ????/**?????*?@param?args
5. ?????*/????public?static?void?main(String[]?args)?{
6. ????????System.out.println("加载Spring配置文件");?????????ApplicationContext?context?=??
7. ????????????????new?ClassPathXmlApplicationContext("spring.xml");??????????System.out.println("加载Spring配置文件结束");
8. ?????????JavaBean?bean=(JavaBean)context.getBean("javaBean");?????????System.out.println("获取name属性："+bean.getName());
9. ?????????System.out.println("程序结束");????}
10. }

Spring配置文件

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<?xml?version="1.0"?encoding="UTF-8"?>?
1. <!DOCTYPE?beans?PUBLIC?"-//SPRING//DTD?BEAN//EN"?"http://www.springframework.org/dtd/spring-beans.dtd"><beans>
2. ????<bean?id="javaBean"?class="com.test.JavaBean"?init-method="init">????????<property?name="name"?value="zhjb"></property>
3. ????</bean>????<bean?id="user"?class="com.test.User"?init-method="init">
4. ????????<property?name="name"?value="zhjb"?></property>????</bean>
5. </beans>

运行结果如下：

加载Spring配置文件
JavaBean类构造方法
JavaBean类setName 方法
BeanFactoryAware 接口 setBeanFactory方法
InitializingBean 接口 afterPropertiesSet方法
JavaBean类init 方法
BeanFactoryPostProcessor 接口 postProcessBeanFactory 方法
User类构造方法
User类 setName方法
user:BeanPostProcessor 接口 postProcessBeforeInitialization 方法
User类init 方法
user:BeanPostProcessor 接口 postProcessAfterInitialization方法
加载Spring配置文件结束
获取name属性：zhjb
程序结束

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从结果进行分析，Bean的初始化顺序应该是

1.构造函数

2.初始化属性

3.如果实现了BeanFactoryAware 接口执行setBeanFactory方法

4..如果实现了InitializingBean 接口执行afterPropertiesSet方法

5.如果在配置文件中指定了init-method，那么执行该方法

6..如果实现了BeanFactoryPostProcessor 接口在 “new”其他类之前执行 postProcessBeanFactory 方法（通过这个方法可以改变配置文件里面的属性值的配置）

7.如果实现了BeanFactoryPostProcessor 接口，那么会在其他bean初始化方法之前执行postProcessBeforeInitialization 方法，之后执行postProcessAfterInitialization方法

感觉奇怪的地方就是没有执行destroy方法，目前还不知道原因在什么地方