Spring5 - Bean的初始化和销毁的4种方式

小小工匠

发布于 2021-08-17 15:56:21

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代码可运行

概述

针对单实例bean的话，容器启动的时候，bean的对象就创建了，而且容器销毁的时候，也会调用Bean的销毁方法
针对原型bean的话,容器启动的时候，bean是不会被创建的而是在获取bean的时候被创建，而且bean的销毁不受 IOC容器的管理.

方式一：自行指定bean的初始化方法和bean的销毁方法

【beans】

package com.artisan.base.lifeCycle;


public class A1 {
	public void init(){
		System.out.println("A1 init");
	}

	public void destory(){
		System.out.println("A1 destory");
	}
}

package com.artisan.base.lifeCycle;


public class A2 {

	public void init(){
		System.out.println("A2 init");
	}

	public void destory(){
		System.out.println("A2 destory");
	}
}

【配置类】

package com.artisan.base.lifeCycle;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;


@Configuration
public class LCConfig {

	@Bean(initMethod = "init",destroyMethod = "destory")
	public A1 a1(){
		return  new A1();
	}

	@Scope("prototype")
	@Bean
	public A2 a2(){
		return  new A2();
	}
}

【测试】

package com.artisan.base.lifeCycle;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import java.util.concurrent.TimeUnit;

/**
 * @author 小工匠
 * @version 1.0
 * @description: TODO
 * @date 2020/10/11 22:58
 * @mark: show me the code , change the world
 */
public class LCTest {
	public static void main(String[] args) throws InterruptedException {
		AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(LCConfig.class);

		TimeUnit.SECONDS.sleep(3);
		// 容器销毁
		ac.close();
	}
}

方式二：通过 InitializingBean和DisposableBean 接口实现bean的初始化以及销毁方法

package com.artisan.base.lifeCycle;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

/**
 * @author 小工匠
 * @version 1.0
 * @description: TODO
 * @date 2020/10/11 23:06
 * @mark: show me the code , change the world
 */
public class A3 implements InitializingBean, DisposableBean {

	public A3() {
		System.out.println("A3 init");
	}

	@Override
	public void destroy() throws Exception {
		System.out.println("A3 destroy");
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		System.out.println("A3 afterPropertiesSet");
	}
}

执行上面的测试代码

方式三：通过JSR250规范提供的注解@PostConstruct 和@ProDestory标注的方法

package com.artisan.base.lifeCycle;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

/**
 * @author 小工匠
 * @version 1.0
 * @description: TODO
 * @date 2020/10/11 23:12
 * @mark: show me the code , change the world
 */
public class A4 {

	public A4() {
		System.out.println("A4 Construct ");
	}

	@PostConstruct
	public void init(){
		System.out.println("A4 init");
	}

	@PreDestroy
	public void destory(){
		System.out.println("A4 destory");
	}
}

测试结果

方式四：通过Spring的BeanPostProcessor的 bean的后置处理器会拦截所有bean创建过程

public class A5 {
	public A5() {
		System.out.println("A5 Construct");
	}

	public void init(){
		System.out.println("A5 init");
	}

	public void destory(){
		System.out.println("A5 destory");
	}
}

【bean後置處理器】

package com.artisan.base.lifeCycle;

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


public class A5BeanPostProcessor implements BeanPostProcessor {
	@Override
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {

		if (bean instanceof  A5){
			System.out.println("A5BeanPostProcessor...postProcessBeforeInitialization:"+beanName);
		}


		return bean;
	}

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

		if (bean instanceof  A5){
			System.out.println("A5BeanPostProcessor...postProcessAfterInitialization:"+beanName);
		}

		return bean;
	}
}

【config】