EL1008E: 在类型为“...User”的对象上找不到属性或字段“username” - 可能不是公共的或无效的？

正如标题所暗示的，我在百里香叶和弹簧的一些实验中遇到了一些问题。这是例外：

org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'username' cannot be found on object of type 'com.black.spring.boot.eventsharing.demo.domain.User' - maybe not public or not valid?

这是我的用户控制器：

@GetMapping
    public ModelAndView list(@RequestParam(value="async",required=false) boolean async,
                             @RequestParam(value="pageIndex",required=false,defaultValue="0") int pageIndex,
                             @RequestParam(value="pageSize",required=false,defaultValue="10") int pageSize,
                             @RequestParam(value="name",required=false,defaultValue="") String name,
                             Model model) {

        Pageable pageable = PageRequest.of(pageIndex, pageSize);
        Page<User> page = userService.listUsersByNameLike(name, pageable);
        List<User> list = page.getContent(); 
        model.addAttribute("page", page);
        model.addAttribute("userList", list);
        for (User user : list) {
            System.out.println("!!!!!!" + user.toString() + "!!!!!");
        }
        return new ModelAndView(async?"users/list :: #mainContainerRepleace":"users/list", "userModel", model);
    }

当我的代码调用控制器时，我做了一些基本的实验，这是系统打印：

!!!!!!User{id=1, name='asd', email='asd@12', username='asd', password='asd', avatar='null'}!!!!!

这是我的 html 代码：

<tr th:each="user : ${userModel.userList}">
    <td th:text="${user.id}">place_holder_id</td>
    <td th:text="${user.username}">place_holder_user_name</td>
    <td th:text="${user.name}">place_holder_name</td>
    <td th:text="${user.email}">place_holder_email</td>
    <td> ...

这是我的 User.java

@Entity
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @NotEmpty(message = "Name should not be empty")
    @Size(min=2, max=20)
    @Column(nullable = false, length = 20)
    private String name;

    @NotEmpty(message = "Email should not be empty")
    @Size(max=50)
    @Email(message= "invalid email format" )
    @Column(nullable = false, length = 50, unique = true)
    private String email;

    @NotEmpty(message = "Username should not be empty")
    @Size(min=3, max=20)
    @Column(nullable = false, length = 20, unique = true)
    private String username;

    @NotEmpty(message = "Password should not be empty")
    @Size(max=100)
    @Column(length = 100)
    private String password;

    @Column(length = 200)
    private String avatar;

    protected User() {
    }

    public User(Long id, String name, String email, String username) {
        this.id = id;
        this.name = name;
        this.email = email;
        this.username = username;
    }

    public String getUserName() { return username; }

    public void setUserName(String username) { this.username = username; }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) { this.password = password; }

    public String getAvatar() { return avatar; }

    public void setAvatar(String avatar) { this.avatar = avatar; }

    public Long getId() { return id; }

    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", email='" + email + '\'' +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", avatar='" + avatar + '\'' +
                '}';
    }
}

我认为错误消息意味着在我的用户中，没有名为“用户名”的属性，但我确实有那个变量。我不确定出了什么问题，任何提示将不胜感激。