Spring SimpSessionScope

@Override
public Object get(String name, ObjectFactory<?> objectFactory) {
   // 获取当前的属性
   SimpAttributes simpAttributes = SimpAttributesContextHolder.currentAttributes();
   // 从属性表中获取对象
   Object scopedObject = simpAttributes.getAttribute(name);
   if (scopedObject != null) {
      return scopedObject;
   }
   // 处理线程问题
   synchronized (simpAttributes.getSessionMutex()) {
      // 从属性表中获取对象
      scopedObject = simpAttributes.getAttribute(name);
      if (scopedObject == null) {
         // 通过 object factory 创建
         scopedObject = objectFactory.getObject();
         // 设置属性
         simpAttributes.setAttribute(name, scopedObject);
      }
      return scopedObject;
   }
}

@Override
@Nullable
public Object remove(String name) {
   SimpAttributes simpAttributes = SimpAttributesContextHolder.currentAttributes();
   synchronized (simpAttributes.getSessionMutex()) {
      Object value = simpAttributes.getAttribute(name);
      if (value != null) {
         simpAttributes.removeAttribute(name);
         return value;
      }
      else {
         return null;
      }
   }
}

@Override
public void registerDestructionCallback(String name, Runnable callback) {
   SimpAttributesContextHolder.currentAttributes().registerDestructionCallback(name, callback);
}



// org.springframework.messaging.simp.SimpAttributes#registerDestructionCallback
	public void registerDestructionCallback(String name, Runnable callback) {
		synchronized (getSessionMutex()) {
			if (isSessionCompleted()) {
				throw new IllegalStateException("Session id=" + getSessionId() + " already completed");
			}
			this.attributes.put(DESTRUCTION_CALLBACK_NAME_PREFIX + name, callback);
		}
	}

@Override
public String getConversationId() {
   return SimpAttributesContextHolder.currentAttributes().getSessionId();
}