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.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>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