Bean 的生命周期

Bean的生命周期主要可分为4个部分：

Bean的定义：通过配置查找Bean，并将Bean定义发布到IoC容器中，此时只有定义==没有实例==
Bean的初始化：创建Bean的实例对象，依赖注入（如@AutoWired等资源）
Bean的生存期：在ctx关闭前存在
Bean的销毁：在ctx关闭后执行销毁

为更直观地测试生命周期，改造Teacher类，加入生命周期接口和自定义类

@Component
public class Teacher implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, InitializingBean, DisposableBean {
    @Autowired
    Student student;
    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        System.out.println("【"+this.getClass().getSimpleName()+"】调用setBeanFactory");
    }

    @Override
    public void setBeanName(String s) {
        System.out.println("【"+this.getClass().getSimpleName()+"】调用setBeanName");
    }

    @Override
    public void destroy() throws Exception {
        System.out.println("【"+this.getClass().getSimpleName()+"】调用destory");
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("【"+this.getClass().getSimpleName()+"】调用afterPropertiesSet");
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        System.out.println("【"+this.getClass().getSimpleName()+"】调用setApplicationContext");
    }
    /**
     * 自定义初始化和销毁操作
     */
    @PostConstruct
    public void init(){
        System.out.println("【"+this.getClass().getSimpleName()+"】执行自定义初始化操作");
    }
    @PreDestroy
    public void des(){
        System.out.println("【"+this.getClass().getSimpleName()+"】执行自定义销毁操作");
    }
}

其中Student类为了观测依赖注入的时间，然后创建BeanPostProcessor实现类，重写其方法：

@Component
public class BeanPostProcessorExample implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization (Object bean, String beanName) throws BeansException {
        System.out.println("▶BeanPostProcessor "+"调用BeforeInitial 【"+bean.getClass().getSimpleName()+"】");
        return bean;
    }
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("▶BeanPostProcessor "+"调用AfterInitial 【"+bean.getClass().getSimpleName()+"】");
        return bean;
    }
}

主方法：

public class DemoApplication {
    public static void main(String[] args)
    {
        AnnotationConfigApplicationContext ctx=new AnnotationConfigApplicationContext(AppConfig.class);
        Teacher tea = ctx.getBean(Teacher.class);
        ctx.close();
    }
}

最终测试结果：

▶BeanPostProcessor 调用BeforeInitial 【AppConfig$$EnhancerBySpringCGLIB$$6fc4ea89】
▶BeanPostProcessor 调用AfterInitial 【AppConfig$$EnhancerBySpringCGLIB$$6fc4ea89】
18:33:15.777 Creating shared instance of singleton bean 'student'
▶BeanPostProcessor 调用BeforeInitial 【Student】
▶BeanPostProcessor 调用AfterInitial 【Student】
18:33:15.778 Creating shared instance of singleton bean 'teacher'
【Teacher】调用setBeanName
【Teacher】调用setBeanFactory
【Teacher】调用setApplicationContext
▶BeanPostProcessor 调用BeforeInitial 【Teacher】
【Teacher】执行自定义初始化操作
【Teacher】调用afterPropertiesSet
▶BeanPostProcessor 调用AfterInitial 【Teacher】
18:33:15.818 ctx - Closing 
【Teacher】执行自定义销毁操作
【Teacher】调用destory

注意：

由于BeanPostProcessor对所有的Bean都生效，因此Appconfig和Student的也会显示出来