spring boot thymeleaf 图片上传web项目根目录操作步骤

//html：
<form enctype="multipart/form-data" method="post" action="/sell/imageUpload">
<div class="modal-header">
 <button type="button" class="close" data-dismiss="modal" aria-hidden="true"> </button>
 <h4 class="modal-title" id="myModalLabel">Edit goods information</h4>
</div>
<div class="modal-body">
 <div class="input-group">
  <label class="col-lg-4">name:</label>
  <input class="col-lg-8" id="edit_name" value="${goods.name}" name="name"/>
 </div>
<div class="input-group">
  <label class="col-lg-4">code:</label>
  <input class="col-lg-8" id="edit_sn" name="sn" value="${goods.sn}" />
 </div>
<div class="input-group">
  <label class="col-lg-4">weight:</label>
  <input class="col-lg-8" id="edit_weight" name="weight" value="${goods.weight}" />
 </div>
<div class="input-group">
  <label class="col-lg-4">marketPrice:</label>
  <input class="col-lg-8" id="edit_marketPrice" name="marketPrice" value="${goods.marketPrice}" />
 </div>
<div class="input-group">
  <label class="col-lg-4">shopPrice:</label>
  <input class="col-lg-8" id="edit_shopPrice" name="shopPrice" value="${goods.shopPrice}" />
 </div>
<div class="input-group">
  <label class="col-lg-4">unit:</label>
  <input class="col-lg-8" id="edit_unit" name="unit" value="${goods.unit}" />
 </div>
<div class="input-group">
  <label class="col-lg-4">number:</label>
  <input class="col-lg-8" id="edit_number" name="number" value="${goods.number}" />
 </div>
 <div class="input-group">
  <label class="col-lg-4">detail:</label>
  <textarea class="col-lg-8" id="edit_detail" name="detail" value="${goods.detail}" />
 </div>
<div class="input-group">
 <!--<form enctype="multipart/form-data" method="post" action="/sell/imageUpload">
  <input ype="hidden" id="edit_goods_sn" name="sn" value="${goods.sn}" />-->
  image<input type="file" id="edit_image" name="file"/>
  <input type="submit" value="upload"/>
 <!--</form>-->
 </div>
</div>
<div class="modal-footer">
 <button type="button" class="btn btn-default" data-dismiss="modal">close</button> 
 <input type="submit" class="btn btn-primary" id="edit_save" value="submit">提交更改</input>
</div>
</form>
//controller
 @RequestMapping(value = "/save",method = RequestMethod.POST)
 public String saveGoodsPage(@RequestParam(value = "id",required=false) String id,@RequestParam(value = "name",required=false) String name,@RequestParam(value = "sn",required=false) String sn,
        @RequestParam(value = "number",required=false) String number,@RequestParam(value = "weight",required=false) String weight,
        @RequestParam(value = "marketPrice",required=false) String marketPrice,@RequestParam(value = "shopPrice",required=false) String shopPrice,
        @RequestParam(value = "unit",required=false) String unit, @RequestParam(value = "detail",required=false) String detail,@RequestParam (value="file")MultipartFile file ) {
 if (!file.isEmpty()) {
  try {
   BufferedOutputStream out = new BufferedOutputStream(
     new FileOutputStream(new File("src/main/resources/static/images/product/" + sn + ".jpg")));//保存图片到目录下
   out.write(file.getBytes());
   out.flush();
   out.close();
   String filename = "\\/images\\/product\\/" + sn + ".jpg";
   /*user.setTupian(filename);
   //userRepository.save(user);//增加用户*/
  } catch (FileNotFoundException e) {
   e.printStackTrace();
   return "upload error," + e.getMessage();
  } catch (IOException e) {
   e.printStackTrace();
   return "upload error" + e.getMessage();
  }
 }
  //...其他操作
 }

 <div th:object="${session.user}">
 <p>Name: <span th:text="*{firstName}">Sebastian</span>.</p>
 <p>Surname: <span th:text="*{lastName}">Pepper</span>.</p>
 <p>Nationality: <span th:text="*{nationality}">Saturn</span>.</p>
 </div>

 <div th:object="${session.user}">
  <p>Name: <span th:text="${session.user.firstName}">Sebastian</span>.</p>
  <p>Surname: <span th:text="${session.user.lastName}">Pepper</span>.</p>
  <p>Nationality: <span th:text="${session.user.nationality}">Saturn</span>.</p>
 </div>

 <div th:object="${session.user}">
  <p>Name: <span th:text="*{firstName}">Sebastian</span>.</p>
  <p>Surname: <span th:text="${session.user.lastName}">Pepper</span>.</p>
  <p>Nationality: <span th:text="*{nationality}">Saturn</span>.</p>
 </div>