Thymeleaf 和 Spring Boot 的下拉列表

Question

我有一个在 HTML 上使用 Thymeleaf 的 Spring Boot 1.3 应用程序。我有用户页面，当我编辑它们时，我希望从列表中选择用户机构。我有正确显示所有内容的窗口，但是当我选择机构时，控制器没有显示所选值。

这是我的 HTML：

 <div class="form-group">
     <label class="col-md-3 control-label">Institution</label>
         <div class="col-md-5">
         <div th:if="${institutionList != null and not #lists.isEmpty(institutionList)}">
             <select>
                 <option th:each="dropDownItem : ${institutionList}"
                                 th:value="${dropDownItem.name}"
                                 th:text="${dropDownItem.name}" />
             </select>
        </div>
        <div th:if="${institutionList == null or lists.isEmpty(institutionList)}">
            <div>"No Institutions were found, please create some first"</div>
        </div>
    </div>
 </div>

这是我的控制器

@Controller
@PreAuthorize("hasRole('Admin')")
@RequestMapping("/admin")
public class AdminController {
    @Transactional
    @PreAuthorize("hasRole('ADMIN')")
    @RequestMapping(value = "/addUser", method = RequestMethod.POST)
    public String checkPersonInfo(@ModelAttribute User user, Model model, Authentication authentication) {
        // user does not have the selected institution set
        customUserDetailsService.createNewUser(user);
        updateModelWithAllUsers(model);
        return "admin";
    }

    private void updateModelWithAllUsers(Model model) {
        model.addAttribute(USERLIST, customUserDetailsService.findAllUsers());
        model.addAttribute(INSTITUTION_LIST, institutionService.findAll());
        model.addAttribute("user", new User());
    }

...
}

这是我的用户：

@Entity
@Table(name = "Users")
public class User implements UserDetails {
 @Id
    private String username;

    @Column(nullable = false)
    private String password;

    private boolean enabled;
    private boolean accountNonExpired;
    private boolean accountNonLocked;
    private boolean credentialsNonExpired;
    private String companyName;
    private String email;

    @ElementCollection(fetch=FetchType.EAGER)
    @CollectionTable(name="Authorities", joinColumns=@JoinColumn(name="username"))
    @Column(name="authority")
    private Set<String> roles = new HashSet<String>();

    @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "institutionId", nullable = false)
    private Institution institution;
... getters & setters
}

还有我的机构：

@Entity
@Table(name = "Institution")
public class Institution {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long institutionId;
    private String name;

    @OneToMany(mappedBy = "institution", fetch = FetchType.EAGER)
    @Fetch(value = FetchMode.SUBSELECT)
    List<User> users = new ArrayList<User>();
    ... getters & setters
}

“/addUser”从UI获取User对象时，机构为空。

编辑 我使用 Sergios 建议使用 select th:field="${user.institution}" 以及 select th:field="*{institution}"

但这给了我一个错误：

org.springframework.validation.BeanPropertyBindingResult: 1 个错误 字段“机构”上的对象“用户”中的字段错误：拒绝值 [com.security.Institution@3e3945d2]；代码 [typeMismatch.user.institution，typeMismatch.institution，typeMismatch.com。 .security.Institution,typeMismatch];论据 [org.springframework.context.support.DefaultMessageSourceResolvable： 代码 [user.institution,institution];论据 [];默认消息 [机构]];默认消息 [无法转换的属性值 键入“java.lang.String”到所需类型“com.security.Institution” 对于财产“机构”；嵌套异常是 org.springframework.core.convert.ConversionFailedException: 失败 从 java.lang.String 类型转换为 java.lang.Long 类型以获得值 'com.security.Institution@3e3945d2';嵌套异常是 java.lang.NumberFormatException：对于输入字符串：“com. .security.Institution@3e3945d2"]

不确定我是否正确阅读，但这是否意味着 Thymeleaf 正在尝试将机构名称传递给 user.institution 字段？

任何人都可以就如何做到这一点提供任何建议吗？

Answer 1

您忘记指明必须从哪个字段获取所选值：

示例：我认为 User 类有一个机构属性。

<div class="form-group">
 <label class="col-md-3 control-label">Institution</label>
     <div class="col-md-5">
     <div th:if="${institutionList != null and not #lists.isEmpty(institutionList)}">
         <select th:field="*{institution}">
             <option th:each="dropDownItem : ${institutionList}"
                             th:value="${dropDownItem.name}"
                             th:text="${dropDownItem.name}" />
         </select>
    </div>
    <div th:if="${institutionList == null or lists.isEmpty(institutionList)}">
        <div>"No Institutions were found, please create some first"</div>
    </div>
</div>

更多信息：http://www.thymeleaf.org/doc/tutorials/2.1/thymeleafspring.html#dropdownlist-selectors

编辑： 您需要向您的应用指示如何将在表单（字符串类型）中返回的机构 ID 转换为机构实体。为此，您必须使用转换器。

首先将option的值改为institutionId：

<div class="form-group">
 <label class="col-md-3 control-label">Institution</label>
     <div class="col-md-5">
     <div th:if="${institutionList != null and not #lists.isEmpty(institutionList)}">
         <select th:field="*{institution}">
             <option th:each="dropDownItem : ${institutionList}"
                             th:value="${dropDownItem.institutionId}"
                             th:text="${dropDownItem.name}" />
         </select>
    </div>
    <div th:if="${institutionList == null or lists.isEmpty(institutionList)}">
        <div>"No Institutions were found, please create some first"</div>
    </div>
</div>

您必须创建一个实现 Converter 接口的类。

@Component
public class StringToInstitution implements Converter<String, Institution> {

@Autowired
private InstitutionRepository repository; //Or the class that implments the repository.

    @Override
    public Institution convert(String arg0) {
        Long id = new Long(arg0);
        return repository.findOne(id);
    }

}