通过Spring @PostConstruct 和 @PreDestroy 方法 实现初始化和销毁bean之前进行的操作

关于在spring 容器初始化 bean 和销毁前所做的操作定义方式有三种：

第一种：通过@PostConstruct 和 @PreDestroy 方法 实现初始化和销毁bean之前进行的操作

第二种是：通过 在xml中定义init-method 和 destory-method方法

第三种是： 通过bean实现InitializingBean和 DisposableBean接口
下面演示通过 @PostConstruct 和 @PreDestory

1:定义相关的实现类：

package com.myapp.core.annotation.init;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

public class PersonService {

    private String  message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    @PostConstruct
    public void  init(){
        System.out.println("I'm init method using @PostConstrut...."+message);
    }

    @PreDestroy
    public void  dostory(){
        System.out.println("I'm destory method using @PreDestroy....."+message);
    }

}

2：定义相关的配置文件：

<?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-3.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd">

<!-- <context:component-scan base-package="com.myapp.core.jsr330"/> -->

<context:annotation-config />

<bean id="personService" class="com.myapp.core.annotation.init.PersonService">
  <property name="message" value="123"></property>
</bean>

</beans>

其中告诉spring 容器采用注解配置：扫描注解配置；

测试类：

package com.myapp.core.annotation.init;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainTest {

    public static void main(String[] args) {

        ApplicationContext  context = new ClassPathXmlApplicationContext("resource/annotation.xml");

        PersonService   personService  =  (PersonService)context.getBean("personService");

        personService.dostory();
    }

}

测试结果：

I’m init method using @PostConstrut….123
I’m destory method using @PreDestroy…..123

其中也可以通过申明加载org.springframework.context.annotation.CommonAnnotationBeanPostProcessor

类来告诉Spring容器采用的 常用 注解配置的方式：

只需要修改配置文件为：

<?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-3.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd">

<!-- <context:component-scan base-package="com.myapp.core.jsr330"/> -->

<!-- <context:annotation-config /> -->


<bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" />
<bean id="personService" class="com.myapp.core.annotation.init.PersonService">
          <property name="message" value="123"></property>
</bean>



</beans>

第二种是：通过 在xml中定义init-method 和 destory-method方法
在xml中配置 init-method和 destory-method方法

只是定义spring 容器在初始化bean 和容器销毁之前的所做的操作

基于xml的配置只是一种方式：

直接上xml中配置文件:

   <bean id="personService" class="com.myapp.core.beanscope.PersonService" scope="singleton"  init-method="init"  destroy-method="cleanUp">

   </bean>

定义PersonService类：

package com.myapp.core.beanscope;


public class PersonService  {
   private String  message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }



    public void init(){
        System.out.println("init");
    }
    // how validate the destory method is a question
    public void  cleanUp(){
        System.out.println("cleanUp");
    }
}

相应的测试类：

package com.myapp.core.beanscope;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainTest {
  public static void main(String[] args) {

      AbstractApplicationContext  context =new  ClassPathXmlApplicationContext("SpringBeans.xml");

    PersonService  person = (PersonService)context.getBean("personService");

    person.setMessage("hello spring");

    PersonService  person_new = (PersonService)context.getBean("personService");

    System.out.println(person.getMessage());
    System.out.println(person_new.getMessage());
    context.registerShutdownHook();


}
} 

测试结果：

init
hello spring
hello spring
cleanUp

可以看出 init 方法和 clean up方法都已经执行了。
context.registerShutdownHook(); 是一个钩子方法，当jvm关闭退出的时候会调用这个钩子方法，在设计模式之 模板模式中 通过在抽象类中定义这样的钩子方法由实现类进行实现，这里的实现类是AbstractApplicationContext，这是spring 容器优雅关闭的方法。

第三种是： 通过bean实现InitializingBean和 DisposableBean接口
1：定义相应类实现InitializingBean ,DisposableBean 接口

package com.myapp.core.annotation.init;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

public class PersonService implements InitializingBean,DisposableBean{

    private String  message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    @Override
    public void destroy() throws Exception {
        // TODO Auto-generated method stub
        System.out.println("I'm init method using implements InitializingBean interface...."+message);

    }

    @Override
    public void afterPropertiesSet() throws Exception {
        // TODO Auto-generated method stub
        System.out.println("I'm init method using implements DisposableBean interface...."+message);

    }


}

2：定义相应的配置文件:

<?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-3.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd">

<!-- <context:component-scan base-package="com.myapp.core.jsr330"/> -->

<!-- <context:annotation-config /> -->


<!-- <bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" /> <bean id="personService" class="com.myapp.core.annotation.init.PersonService"> <property name="message" value="123"></property> </bean> -->

<bean id="personService" class="com.myapp.core.annotation.init.PersonService">
          <property name="message" value="123"></property>
</bean>

</beans>

3：测试类：

package com.myapp.core.annotation.init;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainTest {

    public static void main(String[] args) {

        AbstractApplicationContext  context = new ClassPathXmlApplicationContext("resource/annotation.xml");

        PersonService   personService  =  (PersonService)context.getBean("personService");

             context.registerShutdownHook();
    }

}

4：输出测试结果：

I'm init method using implements DisposableBean interface....123 三月 16, 2013 5:06:34 下午 org.springframework.context.support.AbstractApplicationContext doClose INFO: Closing org.springframework.context.support.ClassPathXmlApplicationContext@205756: startup date [Sat Mar 16 17:06:30 CST 2013]; root of context hierarchy I'm  init  method using implements InitializingBean interface....123