Spring 容器中的 Bean 是有生命週期的，Spring 允許 Bean 在初始化完成後以及銷燬前執行特定的操作。下面是常用的三種指定特定操作的方法：

通過實現InitializingBean/DisposableBean 介面來定製初始化之後/銷燬之前的操作方法；
通過<bean> 元素的 init-method/destroy-method屬性指定初始化之後 /銷燬之前呼叫的操作方法；
在指定方法上加上@PostConstruct或@PreDestroy註解來制定該方法是在初始化之後還是銷燬之前呼叫。

這幾種配置方式，執行順序是怎樣的呢？我們通過例子來研究下：

• Java類：

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class InitAndDestroySeqBean implements InitializingBean, DisposableBean
{
    public
 
 InitAndDestroySeqBean()
    {
        System.out.println("執行InitAndDestroySeqBean: 構造方法");
    }

    @PostConstruct
    public void postConstruct()
    {
        System.out.println("執行InitAndDestroySeqBean: postConstruct");
    }

    @Override
    public void afterPropertiesSet() throws Exception
    {
        System.out.println("執行InitAndDestroySeqBean: afterPropertiesSet"
 
);
    }

    public void initMethod()
    {
        System.out.println("執行InitAndDestroySeqBean: init-method");
    }

    @PreDestroy
    public void preDestroy()
    {
        System.out.println("執行InitAndDestroySeqBean: preDestroy");
    }

    @Override
    public void destroy() throws Exception
    {
        System.out.println("執行InitAndDestroySeqBean: destroy");
    }

    public void destroyMethod()
    {
        System.out.println("執行InitAndDestroySeqBean: destroy-method");
    }

    public static void main(String[] args)
    {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "com/chj/spring/bean.xml");
        context.close();
    }
}

Spring配置檔案：

              <?xml version="1.0" encoding="UTF-8"?>  
                <beans xmlns="http://www.springframework.org/schema/beans"    
                    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    
                     xmlns:context="http://www.springframework.org/schema/context"    
                     xsi:schemaLocation="http://www.springframework.org/schema/beans    
                 http://www.springframework.org/schema/beans/spring-beans-2.5.xsd    
                 http://www.springframework.org/schema/context    
                 http://www.springframework.org/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>

執行InitAndDestroySeqBean的main方法，結果如下：


2013-03-03 17:11:19,098 DEBUG support.DefaultListableBeanFactory - Creating instance of bean 'initAndDestroySeqBean'  

執行InitAndDestroySeqBean: 構造方法  
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()
執行InitAndDestroySeqBean: postConstruct
2013-03-03 17:11:19,129 DEBUG support.DefaultListableBeanFactory - Invoking afterPropertiesSet() on bean with name
‘initAndDestroySeqBean’
執行InitAndDestroySeqBean: afterPropertiesSet
2013-03-03 17:11:19,129 DEBUG support.DefaultListableBeanFactory - Invoking init method ‘initMethod’ on bean with name
‘initAndDestroySeqBean’
執行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[email protected]56a499:
display name
[org[email protected]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.s[email protected]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()
執行InitAndDestroySeqBean: preDestroy
2013-03-03 17:11:19,145 DEBUG support.DisposableBeanAdapter - Invoking destroy() on bean with name ‘initAndDestroySeqBean’
執行InitAndDestroySeqBean: destroy
2013-03-03 17:11:19,145 DEBUG support.DisposableBeanAdapter - Invoking destroy method ‘destroyMethod’ on bean with name
‘initAndDestroySeqBean’
執行InitAndDestroySeqBean: destroy-method

從執行結果可以看出：

Bean在例項化的過程中：Constructor > @PostConstruct >InitializingBean > init-method

Bean在銷燬的過程中：@PreDestroy > DisposableBean > destroy-method