Spring注解@PostConstruct与@PreDestroy

2021-07-12 01:40:22

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

第一种：

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<context:annotation-config />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>

同样可以得到以上测试的输出结果。

----------------------------------------------------------

第二种：

1：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：

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

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