Spring管理Bean的生命周期

笔记内容及代码来源于尚硅谷的免费在线课

地址：http://www.gulixueyuan.com/my/course/46

 

Spring IOC容器对Bean的生命周期进行管理的过程：

1.通过构造器或工厂方法创建Bean实例

2.为Bean的属性设置值和对其他Bean的引用

3.将Bean实例传递给Bean后置处理器的postProcessBeforeInitialization方法

4.调用Bean的初始化方法

5.将Bean实例传递给Bean后置处理器的postProcessAfterInitialization方法

6.Bean可以使用了

7.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="car" class="com.atguigu.spring.beans.cycle.Car"
        init-method="init"
        destroy-method="destroy">
        <property name="brand" value="Audi"></property>
    </bean>
    <!--
        实现BeanPostProcessor接口，并具体提供
        Object postProcessBeforeInitialization(Object bean,String beanName): init-method 之前被调用
        Object postProcessAfterInitialization(Object bean,String beanName): init-metho d 之前被调用

        bean：bean实例本身
        beanName：IOC容器中，配置的bean的名字
        返回值：实际上返回给用户的Bean，可以在以上两个方法中修改返回的bean，甚至返回一个新的bean
    -->
    <!--配置bean的后置处理器：不需要配置id，IOC容器自动识别是一个BeanPostProcessor-->
    <bean class="com.atguigu.spring.beans.cycle.MyBeanPostProcessor"></bean>
</beans>

 

MyBeanPostProcessor.java

package com.atguigu.spring.beans.cycle;

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("postProcessBeforeInitialization: " + bean+","+beanName);
        return bean;
    }

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

        System.out.println("postProcessAfterInitialization: " + bean+","+beanName);

        Car car = new Car();
        car.setBrand("Ford");
        return car;
    }
}

 

Car.java

package com.atguigu.spring.beans.cycle;

public class Car {
    public Car() {
        System.out.println("Car Constructor...");
    }

    private String brand;

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

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

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

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

 

main.java

package com.atguigu.spring.beans.cycle;

import org.springframework.context.ApplicationContext;
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);

        ctx.close();
    }
}