Spring后置处理器之-BeanPostProcessor-蒲公英云

Spring后置处理器之-BeanPostProcessor

Myth丶恋晨 2022-04-18 06:23 338阅读 0赞

在bean初始化前后进行一些处理工作；

BeanPostProcessor【interface】：bean的后置处理器；
方法postProcessBeforeInitialization（）:在初始化之前工作
方法postProcessAfterInitialization（）:在初始化之后工作

*BeanPostProcessor原理

spring源码中的执行顺序：

* populateBean(beanName, mbd, instanceWrapper);给bean进行属性赋值
* initializeBean
* {
* applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
* invokeInitMethods(beanName, wrappedBean, mbd);执行自定义初始化
* applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
*}

* Spring底层对 BeanPostProcessor 的使用

bean赋值，注入其他组件，@Autowired，生命周期注解功能，@Async,xxx;

一、自定义后置处理器

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;
/**
 * 后置处理器：初始化前后进行处理工作
 * 将后置处理器加入到容器中
 * @author lfy
 */
@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("postProcessBeforeInitialization..."+beanName+"=>"+bean);
        return bean;
    }
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("postProcessAfterInitialization..."+beanName+"=>"+bean);
        return bean;
    }
}

二、定义Bean类

1、Bean实现InitializingBean（定义初始化逻辑）， DisposableBean（定义销毁逻辑）接口

import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.stereotype.Component;
@Component
public class Cat implements InitializingBean,DisposableBean {
    public Cat(){
        System.out.println("cat constructor...");
    }
    @Override
    public void destroy() throws Exception {
        // TODO Auto-generated method stub
        System.out.println("cat...destroy...");
    }
    @Override
    public void afterPropertiesSet() throws Exception {
        // TODO Auto-generated method stub
        System.out.println("cat...afterPropertiesSet...");
    }
}

2、自定义init(),destory()方法，@Bean配置@Bean(initMethod=”init”,destroyMethod=”detory”)

package com.atguigu.bean;
import org.springframework.stereotype.Component;
@Component
public class Car {
    public Car(){
        System.out.println("car constructor...");
    }
    public void init(){
        System.out.println("car ... init...");
    }
    public void detory(){
        System.out.println("car ... detory...");
    }
}

3、在初始化方法上面添加：@PostConstruct注解；在销毁方法上面添加： @PreDestroy注解；

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;
@Component
public class Dog {
    public Dog(){
        System.out.println("dog constructor...");
    }
    //对象创建并赋值之后调用
    @PostConstruct
    public void init(){
        System.out.println("Dog....@PostConstruct...");
    }
    //容器移除对象之前
    @PreDestroy
    public void detory(){
        System.out.println("Dog....@PreDestroy...");
    }
}

三、配置类

@ComponentScan("com.atguigu.bean")
@Configuration
public class MainConfigOfLifeCycle {
    //@Scope("prototype")
    @Bean(initMethod="init",destroyMethod="detory")
    public Car car(){
        return new Car();
    }
}

四、测试

import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import com.atguigu.config.MainConfigOfLifeCycle;
public class IOCTest_LifeCycle {
    @Test
    public void test01(){
        //1、创建ioc容器
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfigOfLifeCycle.class);
        System.out.println("容器创建完成...");
        //applicationContext.getBean("car");
        //关闭容器
        applicationContext.close();
    }
}