关于Springboot的扩展点DisposableBean的原理解析

@Slf4j
public class Dog implements InitializingBean, DisposableBean {
    private String name = "wang cai";
    private Food food;
    public Dog() {
        log.info("----Dog的无参构造方法被执行");
    }
    @Autowired
    public void setFood(Food food) {
        this.food = food;
        log.info("----dog的food属性被注入");
    }
    @Override
    public void afterPropertiesSet() throws Exception {
        log.info("----com.fanfu.entity.Dog.afterPropertiesSet触发执行");
    }
    public void myInitMethod() {
        log.info("----com.fanfu.entity.Dog.myInitMethod触发执行");
    }
    @Override
    public void destroy() throws Exception {
        log.info("----com.fanfu.entity.Dog.destroy触发执行");
    }
}

  @Test
    public void test5(){
        log.info("----单元测试执行开始");
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext("com.fanfu");
        log.info("----开始关闭Spring容器");
        context.registerShutdownHook();
        log.info("----Spring容器已经关闭完成");
        log.info("----单元测试执行完毕");
    }

@Override
public void registerShutdownHook() {
   if (this.shutdownHook == null) {
      // 多线程执行容器关闭的操作，主要逻辑在doClose()
      this.shutdownHook = new Thread(SHUTDOWN_HOOK_THREAD_NAME) {
         @Override
         public void run() {
            synchronized (startupShutdownMonitor) {
               doClose();
            }
         }
      };
      Runtime.getRuntime().addShutdownHook(this.shutdownHook);
   }
}

protected void doClose() {
   // Check whether an actual close attempt is necessary...
   if (this.active.get() && this.closed.compareAndSet(false, true)) {
      if (logger.isDebugEnabled()) {
         logger.debug("Closing " + this);
      }
      LiveBeansView.unregisterApplicationContext(this);
      try {
         // Spring容器关闭的时候，会发布一个ContextClosedEvent事件
         publishEvent(new ContextClosedEvent(this));
      }
      catch (Throwable ex) {
         logger.warn("Exception thrown from ApplicationListener handling ContextClosedEvent", ex);
      }
      // 停止Spring bean生命周期里的所有bean
      if (this.lifecycleProcessor != null) {
         try {
            this.lifecycleProcessor.onClose();
         }
         catch (Throwable ex) {
            logger.warn("Exception thrown from LifecycleProcessor on context close", ex);
         }
      }
      //销毁Spring容器内所有缓存的单例bean
      destroyBeans();
      // 关闭Spring容器
      closeBeanFactory();
      onClose();
      if (this.earlyApplicationListeners != null) {
         this.applicationListeners.clear();
         this.applicationListeners.addAll(this.earlyApplicationListeners);
      }
      this.active.set(false);
   }
}

public void destroySingletons() {
   if (logger.isTraceEnabled()) {
      logger.trace("Destroying singletons in " + this);
   }
   synchronized (this.singletonObjects) {
      this.singletonsCurrentlyInDestruction = true;
   }
   String[] disposableBeanNames;
   //所有DisposableBean的实现类都已经在disposableBeans缓存
   synchronized (this.disposableBeans) {
      disposableBeanNames = StringUtils.toStringArray(this.disposableBeans.keySet());
   }
   //这里真接遍历一遍调用，朴实无华
   for (int i = disposableBeanNames.length - 1; i >= 0; i--) {
      destroySingleton(disposableBeanNames[i]);
   }
   this.containedBeanMap.clear();
   this.dependentBeanMap.clear();
   this.dependenciesForBeanMap.clear();
   clearSingletonCache();
}