英文:
@ManyToMany Relationship Between Tables
问题
我有三个单独的实体：`dish（菜品）、kitchen（厨房）、restaurant（餐厅）` 和连接表 `many（多）`。
我的问题是，我如何在我的实体类中定义这种关系？
**厨房模型**
@Entity
@Table(name = "kitchen")
public class Kitchen {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "kitchen_name")
private String name;
@Column(name = "kitchen_photo")
private Blob photo;
}
**菜品模型**
@Entity
@Table(name = "dish")
public class Dish {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "dish_name")
private String dishName;
@Column(name = "dish_photo")
private Blob dishPhoto;
**餐厅模型**
@Entity
@Table(name = "restaurant")
public class Restaurant {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "res_name")
private String name;
@Column(name = "res_rating")
private double rating;
@Column(name = "res_address")
private String address;
@Column(name = "res_number")
private String number;
@Column(name = "res_site")
private String site;
@Column(name = "res_price")
private String price;
@Column(name = "res_photo")
private Blob photo;
连接表
**多对多模型**
@Entity
@Table(name = "many")
public class Many {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "res_id")
private long res_id;
@Column(name = "kitchen_id")
private long kitchen_id;
@Column(name = "dish_id")
private long dish_id;
@Column(name = "many_name")
private String name;
@Column(name = "many_rating")
private double rating;
@Column(name = "many_address")
private String address;
@Column(name = "many_number")
private String number;
@Column(name = "many_site")
private String site;
@Column(name = "many_price")
private String price;
@Column(name = "many_photo")
private Blob photo;
@Column(name = "dish_name")
private String dishName;
@Column(name = "kitchen_name")
private String kitchenName;
@Column(name = "dish_photo")
private Blob dishPhoto;
@Column(name = "kitchen_photo")
private Blob kitchenPhoto;
我知道如何在两个表之间定义这种关系，但对于超过两个表的情况，我不太确定。
我需要创建 `Many` 表吗？
英文:
I have three separate entities dish, kitchen, restaraunt and linking table many.
My question is, how can I define this relation in my entity classes?
Kitchen model
@Entity
@Table(name = "kitchen")
public class Kitchen {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "kitchen_name")
private String name;
@Column(name = "kitchen_photo")
private Blob photo;
}
Dish model
@Entity
@Table(name = "dish")
public class Dish {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "dish_name")
private String dishName;
@Column(name = "dish_photo")
private Blob dishPhoto;
Restaraunt model
public class Restaraunt {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "res_name")
private String name;
@Column(name = "res_rating")
private double rating;
@Column(name = "res_address")
private String address;
@Column(name = "res_number")
private String number;
@Column(name = "res_site")
private String site;
@Column(name = "res_price")
private String price;
@Column(name = "res_photo")
private Blob photo;
Linking table
Many Model
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
@Column(name = "res_id")
private long res_id;
@Column(name = "kitchen_id")
private long kitchen_id;
@Column(name = "dish_id")
private long dish_id;
@Column(name = "many_name")
private String name;
@Column(name = "many_rating")
private double rating;
@Column(name = "many_address")
private String address;
@Column(name = "namy_number")
private String number;
@Column(name = "many_site")
private String site;
@Column(name = "many_price")
private String price;
@Column(name = "many_photo")
private Blob photo;
@Column(name = "dish_name")
private String dishName;
@Column(name = "kitchen_name")
private String kitchenName;
@Column(name = "dish_photo")
private Blob dishPhoto;
@Column(name = "kitchen_photo")
private Blob kitchePhoto;
I know how to define this relationship between two tables, but for more than two I'm not sure.
Am I need to create table Many ?
答案1
得分: 3
Here's the translated code portion:
根据一个 `Restaurant` 可能会有多个 **dishes** 和一个 `Kitchen` 的理解
您可以像下面这样定义关系
@Entity
public class Restaurant {
// 所有其他字段
@OneToMany
private Set<Dish> dishes;
@OneToOne
private Kitchen kitchen;
}
您可以从一侧进行映射，就像上面的示例一样，也可以从两侧进行定义，即从 `Dish` 和 `Kitchen` 两者都定义 - 从 `Dish` 到 `Restaurant` 是 `ManyToOne`，从 `Kitchen` 到 `Restaurant` 是 `OneToOne`
我没有看到使用 `Many` 模型的任何理由。
英文:
Going by the understanding that a Restaurant will have many dishes and one Kitchen
You can define the relationship like below
@Entity
public class Restaraunt {
// all other fields
@OneToMany
private Set<Dish> dishes;
@OneToOne
private Kitchen kitchen;
}
You can have the mapping from one side like above or define it from both sides i.e. from Dish and Kitchen as well - with Dish to Restaurant as ManyToOne and Kitchen to Restaurant as OneToOne
I don't see any reason for having the Many model.
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