Spring_管理bean的生命周期

Spring IOC 容器对 Bean 的生命周期进行管理的过程:
通过构造器或工厂方法创建 Bean 实例
为 Bean 的属性设置值和对其他 Bean 的引用
将 Bean 实例传递给 Bean 后置处理器的 postProcessBeforeInitialization 方法
调用 Bean 的初始化方法
将 Bean 实例传递给 Bean 后置处理器的 postProcessAfterInitialization方法
Bean 可以使用了
当容器关闭时, 调用 Bean 的销毁方法

beans-cycle.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" xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="car" class="com.aff.spring.beans.cycle.Car" init-method="init2" destroy-method="detory">
        <property name="brand" value="Audi" />
    </bean>
    <!--实现 BeanPostProcessor  -->
    <!--配置bean 的后置处理器  并具体实现
              postProcessBeforeInitialization    ：init-method 之前被调用
            postProcessAfterInitialization        ：init-method 之后被调用
            方法的实现
            
            bean  bean 实例本身
            beanName ： IOC 容器配置的bean名字
            返回值： 是实际上返回给用户的哪个bean 注意： 可以在以上两个方法中修改返回bean ， 甚至  返回一个新的bean
      -->
      <!--配置  -->
    <bean class="com.aff.spring.beans.cycle.MyBeanPostProcessor"></bean>

</beans>

MyBeanPostProcessor.java

package com.aff.spring.beans.cycle;

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

public class MyBeanPostProcessor implements BeanPostProcessor {


    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessBeforeInitialization:"+bean+","+beanName);
        if ("car".equals(beanName)) {
            //...
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessAfterInitialization:"+bean+","+beanName);
        Car car = new Car();
        car.setBrand("ford");
        return car;
    }
}

Main

package com.aff.spring.beans.cycle;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
          ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans-cycle.xml");
        Car car = (Car) ctx.getBean("car");
        System.out.println(car);

        // 关闭IOC容器
        ctx.close();
    }
}

 Car

package com.aff.spring.beans.cycle;

public class Car {
    public Car() {
        System.out.println("Car's  Construct...");
    }

    private String brand;

    public void setBrand(String brand) {
        System.out.println("set Brand...");
        this.brand = brand;
    }

    public void init2() {
        System.out.println("init...");
    }

    public void detory() {
        System.out.println("destory ...");
    }

    @Override
    public String toString() {
        return "Car [brand=" + brand + "]";
    }
    
}