无法在 MySQL 中保存对象的 ArrayList - Hibernate/Spring Boot

Question

我认为我在 Hibernate 中的关系映射存在一些问题。这是一个食谱保存应用程序。

最初，recipe 类有一个String ingredients 字段，其中存储了所有成分。我们意识到这对于在配方中存储成分列表没有意义，因此我正在将其重构为我创建的新类型列表Ingredient:List<Ingredient> ingredients。配料表字段由前端的JS动态创建，在POST请求中提交时，转化为新配料的ArrayList，然后添加到Recipe模型中。

每当它到达将其保存到数据库中的行时，我都会收到此错误：

Field 'ingredients' doesn't have a default value，它告诉我该字段为空。但是，当我使用调试工具时，它显示 newRecipe.ingredients 不为空，它实际上是一个从前端数据创建的 ArrayList。

成分类如下所示：

@Entity
public class Ingredient extends AbstractEntity{

    @ManyToOne(targetEntity = Recipe.class,
            fetch = FetchType.LAZY,
            cascade = {CascadeType.MERGE, CascadeType.REMOVE})
    @NotNull(message = "Please include ingredients")
    private Recipe recipe;

    @Id
    @GeneratedValue
    private int id;

    private String ingredient;

    public Ingredient(String ingredient) {
        this.ingredient = ingredient;
    }

    public String getIngredient() {
        return ingredient;
    }

    public void setIngredient(String ingredient) {
        this.ingredient = ingredient;
    }

}

配方类在这里：

@Entity
public class Recipe extends AbstractEntity {

   private String name;

   @OneToMany(mappedBy = "recipe")
   @NotNull(message = "Ingredients required")
   private List<Ingredient> ingredients = new ArrayList<Ingredient>();

   private String directions;

   @OneToMany(mappedBy = "recipe")
   private List<Instruction> instructions = new ArrayList<Instruction>();

   @NotNull(message = "Category required")
   private Category category;

   private Tag tag;

   private String img;

   @OneToMany(mappedBy = "recipe", cascade = {CascadeType.MERGE, CascadeType.REMOVE})
   @NotNull(message = "User is required")
   private List<UserRecipe> users = new ArrayList<>();

   public Recipe() {
   }

   public String getName() {
      return name;
   }

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


   public Category getCategory() {
      return category;
   }

   public void setCategory(Category category) {
      this.category = category;
   }

   public List<UserRecipe> getUsers() {
      return users;
   }

   public void setUsers(List<UserRecipe> users) {
      this.users = users;
   }

   public String getImg() {
      return img;
   }

   public void setImg(String img) {
      this.img = img;
   }


   public List<Ingredient> getIngredients() {
      return ingredients;
   }

   public void setIngredients(List<Ingredient> ingredients) {
      this.ingredients = ingredients;
   }

   public String getDirections() {
      return directions;
   }

   public void setDirections(String directions) {
      this.directions = directions;
   }

   public Tag getTag() {
      return tag;
   }

   public void setTag(Tag tag) {
      this.tag = tag;
   }

   public List<Instruction> getInstructions() {
      return instructions;
   }

   public void setInstructions(List<Instruction> instructions) {
      this.instructions = instructions;
   }
}

RecipeController 在这里：

@PostMapping("create")
   public String createRecipe(HttpServletRequest request, @ModelAttribute Recipe newRecipe,
                              @ModelAttribute @Valid String newCategory,
                              Errors errors, Model model, RedirectAttributes redirectAttrs) {

      if (errors.hasErrors()) {
         model.addAttribute("title", "Create Recipe");
         return "recipes/create";
      }

      String[] ingredients = request.getParameterValues("ingredient");

      List<Ingredient> ingredientsList = new ArrayList<Ingredient>();

      for (int i = 0; i < ingredients.length; i++) {
         Ingredient newIngredient = new Ingredient(ingredients[i]);
         ingredientsList.add(newIngredient);
      }
      newRecipe.setIngredients(ingredientsList);
      
      // THIS PRINTS AN ARRAY OF THE NUMBER OF INGREDIENTS ADDED
      System.out.println(ingredientsList.toString());

      // HERE IS WHERE MY ERROR HAPPENS
      Recipe recipe = recipeRepository.save(newRecipe);
      redirectAttrs.addAttribute("recipeId", recipe.getId());

      return "redirect:/recipes/display";
   }

我的想法是，我在某种程度上没有将成分列表正确映射到食谱，但我无法弄清楚这一点，经过 3 天的谷歌搜索和故障排除后，我来到了这里。任何帮助将不胜感激。提前致谢！

Answer 1

这可能是您的数据库中的架构问题。您是手动创建架构还是使用 auto-ddl？如果您手动创建它，则可能在成分表中缺少 recipe_id 列。如果此类连接列具有不同的名称，则必须在成分类上使用 @JoinColumn 覆盖它，如下所示：

@ManyToOne(targetEntity = Recipe.class,
            fetch = FetchType.LAZY,
            cascade = {CascadeType.MERGE, CascadeType.REMOVE})
    @NotNull(message = "Please include ingredients")
    @JoinColumn("the_recipe_id") // **** Here you put the join column name you specified **** //
    private Recipe recipe;

编辑：另外，你能发布你的 AbstractEntity 类吗？该问题也可能与 Recipe 类中缺少键有关。

Answer 2

我是个白痴。数据库中的数据类型设置不正确。创建一个新的数据库解决了它。