Spring初学之bean的生命周期

实体Bean:

Car.java：

package spring.beans.cycle;

public class Car {
    private String name;
    private int price;

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

    public void init(){//init-method
        System.out.println("init...");
    }
    public void destroy(){//destroy-method
        System.out.println("destroy...");
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        System.out.println("setName...");
        this.name = name;
    }
    public int getPrice() {
        return price;
    }
    public void setPrice(int price) {
        System.out.println("setPrice...");
        this.price = price;
    }

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

}

Spring的配置文件核心代码添加：

    <bean id="car" class="spring.beans.cycle.Car"
    p:name="奥迪" p:price="300000"
    init-method="init"
    destroy-method="destroy">

    </bean>

实现BeanPostProcessor接口，并具体提供两个方法的实现
postProcessAfterInitialization：init-method方法之后调用，
postProcessBeforeInitialization：init-method方法之前调用，
两个参数：
bean:bean实例本身
beanName:IOC容器配置的bean的名字
返回值：是实际上返回给用户的bean，注意：可以在上面两个方法中修改bean，甚至返回一个新的bean。

MyBeanPostProcessor.java：

package spring.beans.cycle;

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

public class MyBeanPostProcessor implements BeanPostProcessor {

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessAfterInitialization"+bean+","+beanName);

        if("...".equals(beanName)){
            //...
        }

        Car car=new Car();
        car.setName("福特");

        return car;
    }

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessBeforeInitialization"+bean+","+beanName);

        Car car=new Car();
        car.setName("长安");

        return car;
    }

}

把这个类配置到spring容器中：

<!-- 配置bean的后置处理器 -->
    <bean class="spring.beans.cycle.MyBeanPostProcessor"></bean>

测试方法：

package spring.beans.cycle.test;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import spring.beans.cycle.Car;

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();
    }

}

输出：

Constructor...
setName...
setPrice...
postProcessBeforeInitializationCar [name=奥迪, price=300000],car
Constructor...
setName...
init...
postProcessAfterInitializationCar [name=长安, price=0],car
Constructor...
setName...
Car [name=福特, price=0]
四月 13, 2017 3:46:13 下午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@3f91beef: startup date [Thu Apr 13 15:46:13 CST 2017]; root of context hierarchy
destroy...