在Thymeleaf中，如何基于当前模型对象为HTML选择器选择th：selected值？

Question

从下面的控制器，我将资源值列表传递serviceRequestList到模型中，即绑定到HTML选择器（下拉菜单）。但是，此页面上存在单个对象ServiceRequestDO。我希望选择器默认为当前对象的值，这样在保存更改时，用户不必记住最初的所有值是什么，然后重置它们。有道理吧？是否存在一些Thymeleaf条件，它将某个字段的当前模型对象的值与应默认选择的选择器相匹配？

ServiceRequestController：

@RequestMapping(value = "edit/{id}", method = RequestMethod.GET)
    String GetEditDetails(Model model, Principal principal, @PathVariable("id") Long id, @Valid @ModelAttribute(value = "requestModel") RequestModel requestModel, BindingResult bindingResult, RedirectAttributes redirectAttributes)
    {
        UserDO currentUser = userRepository.findOneByInitialName(principal.getName());

        // Redirect to index if user is not a manager
        if (currentUser.getRole() != Role.MANAGER) {
            return "redirect:/index";
        }

        ServiceRequestDO service = serviceRequestRepository.findById(id);
        model.addAttribute("service", service);

        model.addAttribute("currentUser", currentUser);
        model.addAttribute("requestModel", new RequestModel());

        List<ServiceRequestTypeResource> serviceRequestList = serviceRequestTypeRepository.findAll();
        List<SubServiceRequestTypeResource> subServiceRequestTypeList = subServiceRequestTypeRepository.findAll();
        List<ServiceLineTypeResource> serviceLineList = serviceLineRepository.findAll();
        List<ProductTypeResource> productList = productRepository.findAll();
        List<CustomerNameTypeResource> customerNameList = customerNameRepository.findAll();
        List<LocalTeamTypeResource> localTeamList = localTeamRepository.findAll();

        serviceRequestList.sort(null);
        subServiceRequestTypeList.sort(null);
        serviceLineList.sort(null);
        productList.sort(null);
        customerNameList.sort(null);
        localTeamList.sort(null);

        /* Drop-Down List */
        model.addAttribute("serviceRequestList", serviceRequestList);
        model.addAttribute("subServiceRequestList", subServiceRequestTypeList);
        model.addAttribute("serviceLineList", serviceLineList);
        model.addAttribute("productList", productList);
        model.addAttribute("customerNameList", customerNameList);
        model.addAttribute("localTeamList", localTeamList);

        return "edit";
    }

HTML：

<tr>
   <td>
      <label rel="tooltip"
         title="" data-placement="bottom" data-html="true">Service Request Type</label>
   </td>
   <td>
      <select th:name="*{serviceRequestType}">
         <option th:each="serviceRequestItem : ${serviceRequestList}"
            th:value="${serviceRequestItem}"
            th:text="${serviceRequestItem}"
            th:selected="${service.serviceRequestType}">
         </option>
      </select>
   </td>
</tr>

使用上面的模板，选择器仅默认为列表中的底部值，例如，无论当前对象模型的值如何${service.serviceRequestType}。

Answer 1

如果我正确理解了所有内容，那么我会那样做（创建了一个简单的示例）：

@GetMapping("/test/{id}")
public String test(Model model, @PathVariable("id") long id) {
    //This part represent your serviceRequestRepository.findById(id);
    User requestedUser = new User(id, "User " + id);
    model.addAttribute("requestedUser", requestedUser);

    //List of users represent your serviceRequestTypeRepository.findAll();
    List<User> users = new ArrayList<>();
    users.add(new User(1, "User 1"));
    users.add(new User(2, "User 2"));
    users.add(new User(3, "User 3"));

    model.addAttribute("users", users);

    return "test";
}

您的选择如下所示：

<select th:name="*{requestedUser}">
  <option th:each="user : ${users}"
     th:value="${user.id}"
     th:text="${user.name}"
     th:selected="${requestedUser.id == user.id}">
  </option>
</select>

如果现在输入http://localhost:8080/test/2，则选择第二个用户：

<option value="1">User 1</option>
<option selected="selected" value="2">User 2</option>
<option value="3">User 3</option>