java - 在Thymeleaf中，我如何选择第:selected value for an HTML selector based on the current model object?

Question

从以下 Controller 中，我将资源值列表(即 serviceRequestList)传递到模型中，然后绑定(bind)一个 HTML 选择器(下拉菜单)。然而，此页面上存在一个对象，ServiceRequestDO。我希望选择器默认为当前对象的值，这样当保存更改时，用户不必记住所有值最初是什么，然后重置它们。有道理，对吧？是否有一些 Thymeleaf 条件可以将某些字段的当前模型对象的值与默认情况下应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>

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

Answer 1

如果我正确理解了一切，我会像这样(创建一个简单的例子):

@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>

如果您现在输入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>