Spring中Bean的生命周期

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可以简述为以下几步

1实例化bean对象(通过构造方法或者工厂方法)

2设置对象属性(setter等)（依赖注入）

3如果Bean实现了BeanNameAware接口，工厂调用Bean的setBeanName()方法传递Bean的ID。（和下面的一条均属于检查Aware接口）

4如果Bean实现了BeanFactoryAware接口，工厂调用setBeanFactory()方法传入工厂自身

5将Bean实例传递给Bean的前置处理器的postProcessBeforeInitialization(Object bean, String beanname)方法

6调用Bean的初始化方法

7将Bean实例传递给Bean的后置处理器的8postProcessAfterInitialization(Object bean, String beanname)方法使用Bean

9容器关闭之前，调用Bean的销毁方法
代码演示
实体类

package com.zdw.Bean;

public class Car {

    private  String brand;

    private  int price;

    @Override
    public String toString() {
        return "Car{" +
                "brand='" + brand + '\'' +
                ", price=" + price +
                '}';
    }

    public Car() {
        System.out.println("1--car这个bean初始化");
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        System.out.println("2--设置对象属性setName");
        this.brand = brand;
    }

    public int getPrice() {
        return price;
    }
    public  void init(){
        System.out.println("3--car bean的初始化");
    }
    public  void destory(){
        System.out.println("5--car bean的 销毁");
    }

    public void setPrice(int price) {
        this.price = price;
    }
    public  void play(){
        System.out.println("4bean的使用");
    }
}

bean的后置处理器,分别在Bean的初始化前后对Bean对象提供自己的实例化逻辑

- 实现BeanPostProcessor接口
    - postProcessBeforeInitialization方法
    - postProcessAfterInitialization方法

package com.zdw.entity;

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

public class MyBeanPostProcessor implements BeanPostProcessor {


    //对初始化之后的Bean进行处理
    //参数：bean：即将初始化的bean
    //参数：beanname：bean的名称
    //返回值：返回给用户的那个bean,可以修改bean也可以返回一个新的bean

    public Object postProcessBeforeInitialization(Object bean, String beanname) throws BeansException {
        System.out.println("postProcessBeforeInitialization"+"----此时我的名字:"+bean);
        return bean;
    }


    public Object postProcessAfterInitialization(Object bean, String beanname) throws BeansException {

        com.zdw.Bean.Car car =null;
        System.out.println("对初始化之后的Bean进行处理,将Bean的成员变量的值修改了");
        System.out.println(" postProcessAfterInitialization");
        if("car".equals(beanname) || bean instanceof Car){
            car= (com.zdw.Bean.Car) bean;
            car.setBrand("Porsche");
        }
        return car;
    }
}

xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:p="http://www.springframework.org/schema/p"

       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-3.0.xsd
      http://www.springframework.org/schema/context
      http://www.springframework.org/schema/context/spring-context.xsd


http://www.springframework.org/schema/mvc ">

        <context:component-scan base-package="com.zdw.Bean"/>



    <bean id="car" class="com.zdw.Bean.Car" init-method="init" destroy-method="destory">
        <property name="brand" value="宝马"/>
        <property name="price" value="999999"/>
    </bean>

    <bean class="com.zdw.entity.MyBeanPostProcessor"></bean>


</beans>

测试

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

        ClassPathXmlApplicationContext ac= new ClassPathXmlApplicationContext("life.xml");

        Car car =ac.getBean("car",Car.class);
        car.play();
        System.out.println(car.toString());

         ac.close();
    }
}

image.png

参考文章:https://blog.csdn.net/w_linux/article/details/80086950
完整代码:https://gitee.com/zdwbmw/itcatguigu_spring
https://www.bilibili.com/video/av50225455/?p=85