老师，下面这段代码，我做的改变仅仅是将返回类型改为 ModelAndView ，将 modelMap 也改成 ModelAndView 类型，所有的 put 改成 addObject 。但是为什么会添加商品页面提交后会有404错误，这跟我使用了哪个类型应该没关吧？感觉这只跟方法上面的两个注解有关。

@RequestMapping(value = "/addproduct", method = RequestMethod.POST)
	@ResponseBody
	private Map<String, Object> addProduct(HttpServletRequest request) {
		Map<String, Object> modelMap = new HashMap<String, Object>();
		// 验证码校验
		if (!CodeUtil.checkVerifyCode(request)) {   
			modelMap.put("success", false);
			modelMap.put("errMsg", "输入了错误的验证码");
			return modelMap;
		}
		// 接收前端参数的变量的初始化，包括商品，缩略图，详情图列表实体类
		ObjectMapper mapper = new ObjectMapper();
		Product product = null;
		ImageHolder thumbnail = null;
		List<ImageHolder> productImgList = new ArrayList<ImageHolder>();
		CommonsMultipartResolver multipartResolver = new CommonsMultipartResolver(
				request.getSession().getServletContext());
		try {
			// 若请求中存在文件流，则取出相关的文件（包括缩略图和详情图）
			if (multipartResolver.isMultipart(request)) {
				thumbnail = handleImage(request, thumbnail, productImgList);
			} else {
				modelMap.put("success", false);
				modelMap.put("errMsg", "上传图片不能为空");
				return modelMap;
			}
		} catch (Exception e) {
			modelMap.put("success", false);
			modelMap.put("errMsg", e.toString());
			return modelMap;
		}
		try {
			String productStr = HttpServletRequestUtil.getString(request, "productStr");
			// 尝试获取前端传过来的表单string流并将其转换成Product实体类
			product = mapper.readValue(productStr, Product.class);
		} catch (Exception e) {
			modelMap.put("success", false);
			modelMap.put("errMsg", e.toString());
			return modelMap;
		}
		// 若Product信息，缩略图以及详情图列表为非空，则开始进行商品添加操作
		if (product != null && thumbnail != null && productImgList.size() > 0) {
			try {
				// 从session中获取当前店铺的Id并赋值给product，减少对前端数据的依赖
				Shop currentShop = (Shop) request.getSession().getAttribute("currentShop");
				product.setShop(currentShop);
				// 执行添加操作
				ProductExecution pe = productService.addProduct(product, thumbnail, productImgList);
				if (pe.getState() == ProductStateEnum.SUCCESS.getState()) {
					modelMap.put("success", true);
				} else {
					modelMap.put("success", false);
					modelMap.put("errMsg", pe.getStateInfo());
				}
			} catch (ProductOperationException e) {
				modelMap.put("success", false);
				modelMap.put("errMsg", e.toString());
				return modelMap;
			}
		} else {
			modelMap.put("success", false);
			modelMap.put("errMsg", "请输入商品信息");
		}
		return modelMap;
	}