Spring深入浅出（三），IoC容器，BeanPostProcessor（Spring后置处理器）

BeanPostProcessor 接口也被称为后置处理器，通过该接口可以自定义调用初始化前后执行的操作方法。

postProcessBeforeInitialization 方法是在 Bean 实例化和依赖注入后，自定义初始化方法前执行的；而 postProcessAfterInitialization 方法是在自定义初始化方法后执行的。

1. 创建实体类

package com.clzhang.spring.demo;

public class HelloWorld {
    private String message;

    public void setMessage(String message) {
        this.message = message;
    }

    public void getMessage() {
        System.out.println("message : " + message);
    }

    public void init() {
        System.out.println("调用XML配置文件中指定的init方法......");
    }
    
    public void destroy() throws Exception {
        System.out.println("调用XML配置文件中指定的destroy方法......");
    }
}

2. 创建BeanPostProcessor接口实现类

package com.clzhang.spring.demo;

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

public class InitHelloWorld implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("InitHelloWorld Before : " + beanName);
        return bean;
    }

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

3. 创建主程序

package com.clzhang.spring.demo;

import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainApp {
    public static void main(String[] args) {
        AbstractApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
        HelloWorld objA = (HelloWorld) context.getBean("helloWorld");
        objA.setMessage("对象A");
        objA.getMessage();
        
        context.registerShutdownHook();
    }
}

4. 配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    
    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-3.0.xsd">

    <bean id="helloWorld" class="com.clzhang.spring.demo.HelloWorld" init-method="init" destroy-method="destroy">
        <property name="message" value="Hello World!" />
    </bean>
    
    <bean class="com.clzhang.spring.demo.InitHelloWorld" />
</beans>

5. 运行

InitHelloWorld Before : helloWorld
调用XML配置文件中指定的init方法......
InitHelloWorld After : helloWorld
message : 对象A
调用XML配置文件中指定的destroy方法......

本文参考：

http://c.biancheng.net/spring/bean-post-processor.html