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一步步剖析spring bean生命周期

 关于spring bean的生命周期,是深入学习spring的基础,也是难点,本篇文章将采用代码+图文结论的方式来阐述spring bean的生命周期,

本篇文章将阐述清楚下图。

 

 一  项目结构及源码

1.程序目录结构

 2.applicationContext.xml

<?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 class="com.demo.dao.UserDao" id="userDao" scope="singleton" init-method="myInit" destroy-method="myDestroy">
        <property name="userName" value="Alan_beijing"/>
    </bean>

    <bean class="com.demo.dao.MyBeanPostProcessor" id="myBeanPostProcessor"/>

</beans>

3.UserDao.java

package com.demo.dao;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.*;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.apache.log4j.Logger;

public class UserDao implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, InitializingBean,
        DisposableBean{

    private String userName;
    private int count = 0;

    public String getUserName() {
        return userName;
    }

    //2.属性注入,注入属性为userName
    public void setUserName(String userName) {
        count++;
        System.out.println(count + ":注入属性userName="+userName);
        this.userName = userName;
    }

    //1.无参构造函数,实例化时调用该构造函数
    public UserDao() {
        count++;
        System.out.println(count + ":调用构造函数UserDao()");
    }

    //3.实现BeanNameAware,获取bean id
    public void setBeanName(String s) {
        count++;
        System.out.println(count + ":调用setBeanName()获取bean id,bean id=" + s);
    }

    //4.实现BeanFactoryAware,获取bean工厂
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        count++;
        System.out.println(count + ":调用setBeanFactory()获取bean工厂,beanFactory=" + beanFactory);
    }

    //5.实现ApplicationContextAware,获取bean上下文
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        count++;
        System.out.println(count + ":调用setApplicationContext()获取bean上下文,applicationContext=" + applicationContext);
    }

    //6.实现InitializingBean,获取afterPropertiesSet
    public void afterPropertiesSet() throws Exception {
        count++;
        System.out.println(count + ":调用afterPropertiesSet()");
    }

    //7.自定义初始化方法myInit()
    public void myInit() {
        count++;
        System.out.println(count + ":调用自定义myInit()");
    }

    //8.实现DisposableBean,获取destroy()
    public void destroy() throws Exception {
        count++;
        System.out.println(count + ":destroy()");
    }

    //9.自定义销毁方法myDestroy()
    public void myDestroy() {
        count++;
        System.out.println(count + ":调用自定义destroy()");
    }
}
4.MyBeanPostProcessor.java
package com.demo.dao;

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

public  class MyBeanPostProcessor implements BeanPostProcessor {
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("=====调用postProcessBeforeInitialization()=====");
        return bean;
    }

    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("=====调用postProcessAfterInitialization()=====");
        return bean;
    }
}

 二  测试代码及测试结果

1.test.java

package com.demo.test;

import com.demo.dao.UserDao;
import org.junit.Test;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {

    @Test
    public void test() {
        //定义容器并初始化
        //ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        AbstractApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        applicationContext.getBean(UserDao.class);
        //只有关闭容器时,才会调用destroy方法
        applicationContext.registerShutdownHook();
    }
}

2.测试结果

 三 分析

通过如上测试结果,bean生命周期流程大致如下:

 

 1.装配bean

bean装配为bean生命周期第一环节。所谓装配bean,指将java对象转换为bean的过程。在该示例中,UserDao.jave和MyBeanPostProcessor通过xml方式转化为bean。

注意:spring框架支持四种方式装配bean:xml方式,java代码方式,自动装配和混合装配方式

2.加载applicationContext.xml并实例化

加载并实例化bean为bean生命周期的第二环节。本文示例通过ClassPathXmlApplicationContext()来加载并,当bean为singleton时,该过程就实例化对象,而不需要等待

调用applicationContext.getBean()获取bean时才实例化对象,这与prototype是不一样的。

3.属性注入

bean属性注入为bean生命周期第三环节,采用反射方式注入bean.

 

4.实现BeanNameAware,获取bean id

该过程为bean生命周期的第四环节,实现该接口,可以获取bean的id

 

5.实现BeanFactoryAware,获取bean 工厂

该过程为bean生命周期第五环节,通过实现BeanFactoryAware获取bean工厂

 6.实现ApplicationContextAware,获取运用上下文

该过程为bean生命周期第六环节,通过实现ApplicationContextAware接口,获取bean上下文

 7.调用Bean后置处理器,before

该过程为bean生命周期第七环节,通过实现后置处理器BeanPostProcessor获取before和after,该过程是通过AOP方式实现的,在before和after之间,发生如下8,9过程。

8.实现InitializingBean的afterPropertiesSet(),获取初始化方法

该过程为bean生命周期第八环节,通过实现InitializingBean,获取afterPropertiesSet()

 9.调用自定义初始化方法,init-method

该过程为bean生命周期第九环节,实现自定义初始化方法

 10.调用Bean后置处理器after

该过程为bean生命周期第十环节,后置处理器最后环节

 11.关闭容器AbstractApplicationContext.registerShutDownHook()

该环节为bean生命周期第十一环节,关闭容器

 

 12.调用DisposableBean的destroy()

该过程为bean生命周期第十二环节,实现DisposableBean接口,调用destroy()

 13.调用定制化销毁方法destroy-method

该过程为bean生命周期最后环节,调用自定义销毁方法destroy-method

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posted @ 2019-10-14 00:17  Alan_beijing  阅读(1405)  评论(0编辑  收藏  举报