如何使用百里香填充下拉菜单？

Question

我有一个小项目，我可以在我的 SQL 数据库中的表中添加类别。 我有另一张表叫做 products。 在“/addProducts”屏幕中，我希望在我的表单中出现一个下拉菜单。 我希望从我的数据库中的“类别”表中的数据填充下拉列表。 但目前我做不到。

因此，如果有人可以帮助我提供一些 thymleaf/html 代码以在我的表单中显示数据，我将不胜感激。

非常感谢任何建议。

PS 我没有使用 DAO 类，也不想硬编码这些值。 只是希望能够直接从数据库中获取数据并将其显示在表单的下拉列表中。谢谢：

1 类别控制器

@Slf4j
@Controller

public class CategoryController implements Serializable {
private CategoryRepository categoryRepository;

public CategoryController(CategoryRepository categoryRepository) {
    this.categoryRepository = categoryRepository;
}

@Autowired
CategoryRepository service;

@Autowired
private UserRepository userRepository;


@GetMapping("/category")
public String displayCategory(Model model) {

    model.addAttribute("category", service.findAll());

    return "/category";
}

@GetMapping("/categoryUserView")
public String displayCategoryUser(Model model) {

    model.addAttribute("category", service.findAll());

    return "/categoryUserView";
}





@PostMapping("/addCategory")
public String processOrder(@Valid Category category, BindingResult result, SessionStatus 
  sessionStatus, Model model) {
    if (result.hasErrors()) {
        return "addCategory";
    }

    service.save(category);
    model.addAttribute("category", service.findAll());
    return "category";
}


@GetMapping("/editCategory/{id}")
public String showUpdateCategoryForm (@PathVariable("id") long id, Model model){
    Category category = service.findAllById(id);
    model.addAttribute("category", category);
    return "editCategory";
}

@PostMapping("/updateCategory/{id}")
public String updateFixtures ( @PathVariable("id") long id, @Valid Category category,
                               BindingResult result, Model model){
    if (result.hasErrors()) {
        category.setId((int) id);
        return "editFixtures";
    }


    service.save(category);
    model.addAttribute("category", service.findAll());
    return "redirect:/category";
}


 @GetMapping("/deleteCategory/{id}")
 public String deleteCategory(@PathVariable("id") long id, Model model) {
    Category category  = categoryRepository.findById(id)
            .orElseThrow(() -> new IllegalArgumentException("Invalid user Id:" + id));
    categoryRepository.delete(category);
    model.addAttribute("category", categoryRepository.findAll());
    return "redirect:/category";
  }
 }

产品控制器

    @Slf4j
    @Controller
    public class ProductController implements Serializable {
    private ProductRepository productRepository;

    public ProductController(ProductRepository productRepository) {
     this.productRepository = productRepository;
     };


    @Autowired
    ProductRepository service;

    @Autowired
    private UserRepository userRepository;


    @GetMapping("/products")
    public String displayCategory(Model model) {

     model.addAttribute("product", service.findAll());

    return "/product";
   }


   @GetMapping("/addProduct")
   public String showSignUpForm(SessionStatus sessionStatus,
                             @AuthenticationPrincipal User user, Product product, Model 
    model) {

        model.addAttribute("category",service.findAll());


    return "addProduct";
   }

   @PostMapping("/addProduct")
   public String processOrder(@Valid Product product, BindingResult result, SessionStatus 
    sessionStatus, Model model) {
    if (result.hasErrors()) {
        return "addProduct";
    }

    //category.setUser(user);
    service.save(product);
    model.addAttribute("product", service.findAll());
    return "product";
    }

   }

类别模型

   @Data
   @Entity
   @Table(name = "product_categories")
   public class Category {

   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = "product_category_id")
   private long id;

   @Column(name = "category_name")
   private String name;

   @Column(name = "category_description")
   private String desc;


   public long getId() {
    return id;
   }

     public void setId(int id) {
     this.id = id;
     }

    public String getName() {
    return name;
    }

    public void setName(String name) {
     this.name = name;
   }

    public String getDesc() {
     return desc;
   }

    public void setDesc(String desc) {
    this.desc = desc;
    }
    }

产品型号

    @Data
    @Entity
    @Table(name = "product")
     public class Product {


    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "product_id")
    private long id;

    @OneToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "product_id", referencedColumnName = "product_category_id")
    public Category category;

    @Column(name = "product_name")
    private String name;

    @Column(name = "producy_description")
    private String desc;

    @Column(name = "producy_quanitity")
    private int quantity;

    @Column(name = "producy_price")
    private double price;
   }
  }

添加产品 HTML

    <h1> Add your Products Here</h1>

   <form method="POST" th:action="@{/addProduct}" class="form- 
    container" id="aboutForm">
   
   <div class="form-group col-md-8">
   <label  class="col-form-label">Category </label>
   <select  id="category" name="category" th:field="*{category.id}" >
    <option th:each="category : ${category}" th:value="${category.id}" 
    th:utext="${category.name}"/>
    </select>
   </div>
 </form>

HTML 出错

    Bean property 'id' is not readable or has an invalid getter 
    method: 
    Does the return type of the getter match the parameter type 

Answer 1

如错误消息中所述，您在 getter 和 setter 方法中使用了两种不同的数据类型。您可以尝试从

更新您的二传手吗

 public void setId(int id) {
 this.id = id;
 }

到这里

 public void setId(long id) {
 this.id = id;
 }

注意：希望你没有尝试过。

Answer 2

所以我遵循了提供的建议。 我创建了一个列表并在我的存储库中使用 findAll 方法在下拉列表中显示所有内容。

谢谢