spring bean的生命周期

一、初始化和销毁

1、项目结构如下：

2、新建ReplyService类

package hjp.spring.beanlifecycle;

public class ReplyService {
    public void addReply() {
        System.out.println("add replay");
    }
    public void myInit(){
        System.out.println("init方法");
    }
    public void myDestroy(){
        System.out.println("destroy 方法");
    }
}

3、新建beans.xml文档，init-method指定初始化时执行方法，destroy-method指定bean销毁时执行方法

注意：销毁方法要求：(1)、必须是单例的(2)、必须关闭容器

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
                              http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="replyServiceId" class="hjp.spring.beanlifecycle.ReplyService" init-method="myInit" destroy-method="myDestroy"></bean>
</beans>

4、新建测试类

package hjp.spring.beanlifecycle;

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

public class TestApp {
    @Test
    public void demo1(){
        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("hjp/spring/beanlifecycle/beans.xml");
        ReplyService replyService = applicationContext.getBean("replyServiceId", ReplyService.class);
        replyService.addReply();
        applicationContext.close();
    }
}

二、后处理bean

1、spring 后处理bean提供一种机制，可以对实例对象进行修改的机制

2、后处理bean使用

 (1)、编写实现类，实现接口BeanPostProcessor

package hjp.spring.beanlifecycle;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

public class MyBeanPostProcessor implements BeanPostProcessor {

    /**
     * postProcessAfterInitialization 初始化方法（也就是示例中myInit方法）之前执行
     * postProcessBeforeInitialization 初始化方法（也就是示例中myInit方法）之后执行
     * bean 指spring创建的实例对象,即相当于beans中配置节点bean的属性class实例化对象
     * beanName 指spring 创建实例名称，即beans中配置节点bean的属性Id;可以通过beanName对bean进行过滤处理
     * 如果不进行任何操作，必须将bean进行返回，否则报空指针错误
     */

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("初始化前");
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("初始化后");
        return bean;
    }
}

 (2)、将实现类配置到spring容器，spring容器在创建bean时，都是自动使用后处理bean

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
                              http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!-- 创建目标类 -->
    <bean id="replyServiceId" class="hjp.spring.beanlifecycle.ReplyService"
        init-method="myInit" destroy-method="myDestroy"></bean>
    <!-- 配置后处理bean，只需配置class，spring将自动使用 -->
    <bean class="hjp.spring.beanlifecycle.MyBeanPostProcessor"></bean>
</beans>