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