9.Bean的生命周期

package com.xkj.org;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

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

@Component
public class LifeCycleBean {


    public LifeCycleBean() {
        System.out.println(("构造..."));
    }

    @Autowired
    public void autowire(@Value("${JAVA_HOME}") String home) {
        System.out.println("依赖注入："+ home);
    }

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

    @PreDestroy
    public void destroy() {
        System.out.println("销毁....");
    }


}

ConfigurableApplicationContext context = SpringApplication.run(ReggieApplication.class, args);
        //关闭容器，观察bean的生命周期
        context.close();

执行流程： Bean的构造方法->@Autowired依赖注入->Bean的初始化方法->容器关闭->Bean的销毁方法

扩展点：

package com.xkj.org;

import org.springframework.beans.BeansException;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor;
import org.springframework.stereotype.Component;

@Component
public class MyBeanPostProcessor implements InstantiationAwareBeanPostProcessor, DestructionAwareBeanPostProcessor {
    @Override
    public void postProcessBeforeDestruction(Object bean, String beanName) throws BeansException {
        if(beanName.equals("lifeCycleBean")) {
            System.out.println("销毁之前执行，如@PreDestroy");
        }
    }

    @Override
    public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
        if(beanName.equals("lifeCycleBean")) {
            System.out.println("实例化之前执行，这里返回的对象不为null会替换掉原本的Bean");
        }
        return null;
    }

    @Override
    public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
        if(beanName.equals("lifeCycleBean")) {
            System.out.println("实例化之后执行，这里如果返回false，会跳过依赖注入");
//            return false;
        }
        return true;
    }

    @Override
    public PropertyValues postProcessProperties(PropertyValues pvs, Object bean, String beanName) throws BeansException {
        if(beanName.equals("lifeCycleBean")) {
            System.out.println("依赖注入阶段执行，如@Autowired @Value @Resource,扩展的比较多");
        }
        return pvs;
    }

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if(beanName.equals("lifeCycleBean")) {
            System.out.println("初始化之前执行，这里返回的对象会替换掉原本的bean, 如@PostConstruct @ConfigurationProperties");
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if(beanName.equals("lifeCycleBean")) {
            System.out.println("初始化之后执行，这里返回的对象会替换掉原本的Bean,如代理增强");
        }
        return bean;
    }
}