spring-注解---LifeCylce

Posted 2021-01-15 周无极

（2）     spring-注解---LifeCylce

 

package com.zwj.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...");
    }

}

Car

package com.zwj.bean;

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...");
    }

    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...");
    }

}

Cat

package com.zwj.bean;

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 implements ApplicationContextAware {
    
    //@Autowired
    private ApplicationContext applicationContext;
    
    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...");
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        // TODO Auto-generated method stub
        this.applicationContext = applicationContext;
    }


    

}

Dog

package com.zwj.bean;

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;
    }

}

MyBeanPostProcessor

package com.zwj.config;

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

import com.zwj.bean.Car;


/**
 * bean的生命周期：
 *         bean创建---初始化----销毁的过程
 * 容器管理bean的生命周期；
 * 我们可以自定义初始化和销毁方法；容器在bean进行到当前生命周期的时候来调用我们自定义的初始化和销毁方法
 * 
 * 构造（对象创建）
 *         单实例：在容器启动的时候创建对象
 *         多实例：在每次获取的时候创建对象\\
 * 
 * BeanPostProcessor.postProcessBeforeInitialization
 * 初始化：
 *         对象创建完成，并赋值好，调用初始化方法。。。
 * BeanPostProcessor.postProcessAfterInitialization
 * 销毁：
 *         单实例：容器关闭的时候
 *         多实例：容器不会管理这个bean；容器不会调用销毁方法；
 * 
 * 
 * 遍历得到容器中所有的BeanPostProcessor；挨个执行beforeInitialization，
 * 一但返回null，跳出for循环，不会执行后面的BeanPostProcessor.postProcessorsBeforeInitialization
 * 
 * BeanPostProcessor原理
 * 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);
 *}
 * 
 * 
 * 
 * 1）、指定初始化和销毁方法；
 *         通过@Bean指定init-method和destroy-method；
 * 2）、通过让Bean实现InitializingBean（定义初始化逻辑），
 *                 DisposableBean（定义销毁逻辑）;
 * 3）、可以使用JSR250；
 *         @PostConstruct：在bean创建完成并且属性赋值完成；来执行初始化方法
 *         @PreDestroy：在容器销毁bean之前通知我们进行清理工作
 * 4）、BeanPostProcessor【interface】：bean的后置处理器；
 *         在bean初始化前后进行一些处理工作；
 *         postProcessBeforeInitialization:在初始化之前工作
 *         postProcessAfterInitialization:在初始化之后工作
 * 
 * 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 BeanPostProcessor;
 * 
 * @author lfy
 *
 */
@ComponentScan("com.zwj.bean")
@Configuration
public class MainConfigOfLifeCycle {
    
    //@Scope("prototype")
    @Bean(initMethod="init",destroyMethod="detory")
    public Car car(){
        return new Car();
    }

}

MainConfigOfLifeCycle

package com.zwj.test;

import org.junit.Test;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.zwj.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();
    }

}
/**
car constructor...
postProcessBeforeInitialization...car=>com.zwj.bean.Car@41ee392b
car ... init...
postProcessAfterInitialization...car=>com.zwj.bean.Car@41ee392b
cat constructor...
postProcessBeforeInitialization...cat=>com.zwj.bean.Cat@667a738
cat...afterPropertiesSet...
postProcessAfterInitialization...cat=>com.zwj.bean.Cat@667a738
dog constructor...
postProcessBeforeInitialization...dog=>com.zwj.bean.Dog@400cff1a
Dog....@PostConstruct...
postProcessAfterInitialization...dog=>com.zwj.bean.Dog@400cff1a
容器创建完成...
*/

IOCTest_LifeCycle

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.zwj</groupId>
    <artifactId>spring-annotation</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.12.RELEASE</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

    </dependencies>
</project>

pom.xml