Spring容器中的Bean几种初始化方法和销毁方法的先后顺序

Spring 容器中的 Bean 是有生命周期的，Spring 允许 Bean 在初始化完成后以及销毁前执行特定的操作。下面是常用的三种指定特定操作的方法：

• 通过实现InitializingBean/DisposableBean 接口来定制初始化之后/销毁之前的操作方法；
• 通过<bean> 元素的 init-method/destroy-method属性指定初始化之后 /销毁之前调用的操作方法；
• 在指定方法上加上@PostConstruct或@PreDestroy注解来制定该方法是在初始化之后还是销毁之前调用。

这几种配置方式，执行顺序是怎样的呢？我们通过例子来研究下：

Java类：

import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; import org.springframework.beans.factory.DisposableBean; import org.springframework.beans.factory.InitializingBean; import org.springframework.context.support.ClassPathXmlApplicationContext; public class InitAndDestroySeqBean implements InitializingBean,DisposableBean { public InitAndDestroySeqBean(){ System.out.println('执行InitAndDestroySeqBean: 构造方法'); } @PostConstruct public void postConstruct() { System.out.println('执行InitAndDestroySeqBean: postConstruct'); } @Override public void afterPropertiesSet() throws Exception { System.out.println('执行InitAndDestroySeqBean: afterPropertiesSet'); } public void initMethod() { System.out.println('执行InitAndDestroySeqBean: init-method'); } @PreDestroy public void preDestroy() { System.out.println('执行InitAndDestroySeqBean: preDestroy'); } @Override public void destroy() throws Exception { System.out.println('执行InitAndDestroySeqBean: destroy'); } public void destroyMethod() { System.out.println('执行InitAndDestroySeqBean: destroy-method'); } public static void main(String[] args) { ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext('com/chj/spring/bean.xml'); context.close(); } }

Spring配置文件：

<?xml version='1.0' encoding='UTF-8'?> <beans xmlns='http://www./schema/beans' xmlns:xsi='http://www./2001/XMLSchema-instance' xmlns:context='http://www./schema/context' xsi:schemaLocation='http://www./schema/beans http://www./schema/beans/spring-beans-2.5.xsd http://www./schema/context http://www./schema/context/spring-context-2.5.xsd'> <context:annotation-config/> <bean id='initAndDestroySeqBean' class='com.chj.spring.InitAndDestroySeqBean' init-method='initMethod' destroy-method='destroyMethod'/> </beans>

运行InitAndDestroySeqBean的main方法，结果如下：

2013-03-03 17:11:19,098 DEBUG support.DefaultListableBeanFactory - Creating instance of bean 'initAndDestroySeqBean' 执行InitAndDestroySeqBean: 构造方法 2013-03-03 17:11:19,114 DEBUG annotation.CommonAnnotationBeanPostProcessor - Found init method on class [com.alibaba.chj.spring.InitAndDestroySeqBean]: public void com.alibaba.chj.spring.InitAndDestroySeqBean.postConstruct() 2013-03-03 17:11:19,114 DEBUG annotation.CommonAnnotationBeanPostProcessor - Found destroy method on class [com.alibaba.chj.spring.InitAndDestroySeqBean]: public void com.alibaba.chj.spring.InitAndDestroySeqBean.preDestroy() 2013-03-03 17:11:19,129 DEBUG support.DefaultListableBeanFactory - Eagerly caching bean 'initAndDestroySeqBean' to allow for resolving potential circular references 2013-03-03 17:11:19,129 DEBUG annotation.CommonAnnotationBeanPostProcessor - Invoking init method on bean 'initAndDestroySeqBean': public void com.alibaba.chj.spring.InitAndDestroySeqBean.postConstruct() 执行InitAndDestroySeqBean: postConstruct 2013-03-03 17:11:19,129 DEBUG support.DefaultListableBeanFactory - Invoking afterPropertiesSet() on bean with name 'initAndDestroySeqBean' 执行InitAndDestroySeqBean: afterPropertiesSet 2013-03-03 17:11:19,129 DEBUG support.DefaultListableBeanFactory - Invoking init method  'initMethod' on bean with name 'initAndDestroySeqBean' 执行InitAndDestroySeqBean: init-method 2013-03-03 17:11:19,129 DEBUG support.DefaultListableBeanFactory - Finished creating instance of bean 'initAndDestroySeqBean' 2013-03-03 17:11:19,129 INFO  support.ClassPathXmlApplicationContext - Closing org.springframework.context.support.ClassPathXmlApplicationContext@56a499: display name [org.springframework.context.support.ClassPathXmlApplicationContext@56a499]; startup date [Sun Mar 03 17:11:17 CST 2013]; root of context hierarchy 2013-03-03 17:11:19,129 INFO  support.DefaultListableBeanFactory - Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1292d26: defining beans [org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,initAndDestroySeqBean]; root of factory hierarchy 2013-03-03 17:11:19,129 DEBUG annotation.CommonAnnotationBeanPostProcessor - Invoking destroy method on bean 'initAndDestroySeqBean': public void com.alibaba.chj.spring.InitAndDestroySeqBean.preDestroy() 执行InitAndDestroySeqBean: preDestroy 2013-03-03 17:11:19,145 DEBUG support.DisposableBeanAdapter - Invoking destroy() on bean with name 'initAndDestroySeqBean' 执行InitAndDestroySeqBean: destroy 2013-03-03 17:11:19,145 DEBUG support.DisposableBeanAdapter - Invoking destroy method 'destroyMethod' on bean with name 'initAndDestroySeqBean' 执行InitAndDestroySeqBean: destroy-method

从执行结果可以看出：

Bean在实例化的过程中：Constructor > @PostConstruct >InitializingBean > init-method

Bean在销毁的过程中：@PreDestroy > DisposableBean > destroy-method