Spring thymeleaf MVC 表单不填充对象字段

Question

我在 Spring MVC 应用程序中从 thymeleaf 表单中检索值时遇到问题。这个应用程序有多种形式，除了一种之外都可以正常工作。失败的稍有不同，因为它有一个从对象列表提供的下拉列表。 UI 工作正常，问题是 POST 不包含模型属性中的任何数据。

这是两个 POJO，第一个是下拉列表后面的：

@Entity
@Table(name = "musicgenre")
public class MusicGenre {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String genre;

    public MusicGenre() {
    }

    public MusicGenre(String genre) {
        this.genre = genre;
    }

    public Integer getId() {
        return id;
    }

    public String getGenre() {
        return genre;
    }

    @Override
    public String toString() {
        return "MusicGenre{" +
                "id=" + id +
                ", genre='" + genre + '\'' +
                '}';
    }
}

还有要填写的：

@Entity
@Table(name = "musicwish")
public class MusicWish {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String artist;
    private String song;
    private Integer genreId;
    private String notes;

    public MusicWish() {
    }

    public Integer getId() {
        return id;
    }

    public String getArtist() {
        return artist;
    }

    public String getSong() {
        return song;
    }

    public Integer getGenreId() {
        return genreId;
    }

    public String getNotes() {
        return notes;
    }

    @Override
    public String toString() {
        return "MusicWish{" +
                "id=" + id +
                ", artist='" + artist + '\'' +
                ", song='" + song + '\'' +
                ", genreId=" + genreId +
                ", notes='" + notes + '\'' +
                '}';
    }

    private MusicWish(final Builder builder) {
        this.artist = builder.artist;
        this.song = builder.song;
        this.genreId = builder.genreId;
        this.notes = builder.notes;
    }

    public static class Builder {
        private String artist;
        private String song;
        private Integer genreId;
        private String notes;
        public Builder withArtist(final String artist) { this.artist = artist; return this; }
        public Builder withSong(final String song) { this.song = song; return this; }
        public Builder withGenreId(final Integer genre) { this.genreId = genre; return this; }
        public Builder withNotes(final String notes) { this.notes = notes; return this; }
    }
}

我省略了服务类，因为它工作正常。控制器：

@Controller
public class MusicController {

    @Autowired
    private MusicService musicService;

    @RequestMapping(path = "/music-wishlist", method = RequestMethod.GET)
    public ModelAndView getMusicWishlist(Model model) {
        ModelAndView modelAndView = new ModelAndView("music-wishlist");
        modelAndView.addObject("wishes", musicService.getWishes());
        modelAndView.addObject("genres", musicService.getGenreMap());
        return modelAndView;
    }

    @RequestMapping(path = "/music-wish", method = RequestMethod.GET)
    public ModelAndView getMusicWish(Model model) {
        ModelAndView modelAndView = new ModelAndView("music-wish");
        modelAndView.addObject("musicWish", new MusicWish());
        modelAndView.addObject("genreList", musicService.getGenres());
        return modelAndView;
    }

    @RequestMapping(path = "/music-wish", method = RequestMethod.POST)
    public ModelAndView postMusicWish(
            @ModelAttribute("musicWish") MusicWish musicWish) {
        ModelAndView modelAndView = new ModelAndView("music-wishlist");
        modelAndView.addObject("wishes", musicService.getWishes());
        modelAndView.addObject("genres", musicService.getGenreMap());
        return modelAndView;
    }
}

最后是 HTML sn-p 格式：

        <form th:action="@{/music-wish}"
              th:object="${musicWish}"
              method="post"
              class="registration-text">

            <p class="registration-input-label"
               th:text="#{music.artist}"></p>
            <input type="text"
                   class="registration-input-text"
                   th:field="*{artist}"/>

            <p class="registration-input-label"
               th:text="#{music.song}"></p>
            <input type="text"
                   class="registration-input-text"
                   th:field="*{song}"/>

            <p class="registration-input-label"
               th:text="#{music.genre}"></p>
            <select th:field="*{genreId}">
                <option
                        th:each="genre: ${genreList}"
                        th:value="${genre.id}"
                        th:text="${genre.genre}" ></option>
            </select>

            <p class="registration-input-label"
               th:text="#{music.notes}"></p>
            <input type="text"
                   class="registration-input-text"
                   th:field="*{notes}"/>
            <p style="margin-top: 20px;">
                <input type="submit" th:value="#{button.submit}" />
                <input type="reset" th:value="#{button.reset}" />
            </p>
        </form>

问题是当 POST 处理程序接收到 musicWish 时，所有字段仍然为空。 相同的模式在其他形式中也可以正常工作，但在这里失败......即使我将下拉列表注释掉。对于识别我在这里放置的错误的任何帮助，我将不胜感激。

谢谢，

斯蒂芬

Answer 1

您的视图模型属性没有任何 setter ，您需要为要绑定的字段提供公共 setter

Answer 2

您的 MusicWish 和 MusinGenre 类不包含任何用于设置值的公共 setter 方法。

我想建议你使用 LOMBOK jar 来制作更干净的代码。这样可以避免在课堂上提及 getter 和 Setter 以及构造函数。但是，只需定义@Getter、@Setter、@NoArgsConstructor 和@AllArgsConstructor，它将支持您的所有功能。例如，

@Entity
@Table(name = "musicgenre")
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class MusicGenre {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String genre;
}