Java Thymeleaf下拉菜单

我正在尝试在我的表单中创建一个下拉列表。我的用户输入的文本输入显示出来，但是，我的枚举下拉列表没有列出这些值。我知道这里还有其他关于同一主题的帖子（我已经读过），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...

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;
    }
}

我找到了解决办法

 <form action="#" th:action="@{${isAdd}?'/save':'/update'}" th:object="${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 : ${T(com.abbyhowe.LearnFolio.models.UserType).values()}"
                                th:value="${type}"
                                th:text="${type.displayName}">
                        </option>
                    </select>
                </div>

它不起作用。我将添加刚才在上述代码示例中尝试的内容。好的-明白。你能帮我澄清一下“它不起作用”吗？呈现什么HTML？是否有任何错误消息？首先，感谢您的帮助。在上面HTML的第三部分中，我可以显示下拉列表，但下拉列表中没有任何值。我想知道th:value或th:text值是否编码错误？在这一点上，我没有收到任何使故障排除变得困难的错误消息@安德烈·詹姆斯

@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;

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;
    }
}

 <form action="#" th:action="@{${isAdd}?'/save':'/update'}" th:object="${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 : ${T(com.abbyhowe.LearnFolio.models.UserType).values()}"
                                th:value="${type}"
                                th:text="${type.displayName}">
                        </option>
                    </select>
                </div>