Thymeleaf下拉菜单

Question

我正在尝试在表单中创建一个下拉列表。用户输入的文本输入正在显示，但是我的枚举下拉列表未列出这些值。我知道这里还有关于同一主题的其他帖子（我已经阅读过），但似乎仍然无法显示下拉列表。有人能帮我吗？这就是我尝试过的...

            <form action="#" th:action="@$isAdded?'/save':'/update'" th:object="$user" method="post" enctype="multipart/form-data">

                Dropdown for User type or role
                <div class="form-group" >
                    <select th:field="*type">
                        <option
                                th:each="type : $UserType.values()"
                                th:value="$type"
                                th:text="$type">
                        </option>
                    </select>
                </div>


                <div class="form-group">
                    <input type="text", class="form-control" id="firstName" placeholder="First Name" th:field="*firstName">
                </div>
.... The remaining text inputs have been omitted...

我也基于此StackOverflow Post...How to display all possible enum values in a dropdown list using Spring and Thymeleaf?尝试过

 <div class="form-group" >
                    <select th:field="*type">
                        <option
                                th:each="type : $T(com.abbyhowe.LearnFolio.models.User.type).values()"
                                th:value="$type"
                                th:text="$type">
                        </option>
                    </select>
                </div>

这将显示下拉列表，但没有将类型列表显示为可选选项。

<div class="form-group" >
                    <select th:field="*type">
                        <option
                                th:each="type : $types"
                                th:value="$type"
                                th:text="$type">
                        </option>
                    </select>
                </div>

这是我的User类。

@Entity
@Table(name="user")
public class User implements Serializable 

    /***
     *
     */
    private static final long serialVersionUID = -8885466378515990394L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;

    @NotBlank(message = "First name is required")
    @Size(min = 2, max = 50, message = "Name must be between 3 and 50 characters")
    @Column(name = "first_name")
    private String firstName;

    @Column(name = "type")
    private UserType type;

这是我的枚举用户类型...

public enum UserType 
    TEACHER("Teacher"),
    STUDENT("Student"),
    ADMIN("Account Administrator");

    private final String displayName;

    UserType(String displayName) 
        this.displayName = displayName;
    

    public String getDisplayName() 
        return displayName;