Spring容器中定義Bean幾種初始化方法和銷燬方法
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 hierarchy2013-03-03 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