JPA ：对生成的 JoinTable 的引用

Question

我有两个实体：Product 和 Aisle。一个产品可以在一个或多个通道中，一个通道可以有一个或多个产品。

@Entity 

public class Product{

   @Id

   private Long id;

   private String name;

   @ManyToMany

   @JoinTable(name = "product_aisle",

            joinColumns = { @JoinColumn(name = "product_id") },

            inverseJoinColumns = { @JoinColumn(name = "aisle_id") })

    private Set<Aisle> aisles = new HashSet<>();

   /* getters, setters, equals and hashcode */

}

@Entity 

public class Aisle{

   @Id

   private Long id;

   private String row;

   private String shelf;

   @ManyToMany(mappedBy="aisles")

   private Set<Product> products = new HashSet<>();

   /* getters, setters, equals and hashcode */

}

我还有最后一个实体：推销员。销售员负责过道中的产品：

@Entity 

public class Salesman{

   @Id

   private Long id;

   private String name;

   /* ManyToOne to  ProductAisle ?*/

}

问题：如何使用“@ManyToOne”注释将销售员引用到自动创建的连接表 (ProductAisle)？

Answer 1

要表示Product特定中的 a，Aisle您需要另一个实体。这是一个例子：@Entity&nbsp;public class Product{&nbsp; &nbsp;@Id&nbsp; &nbsp;private Long id;&nbsp; &nbsp;private String name;&nbsp; &nbsp;@OneToMany(mappedBy = "product")&nbsp; &nbsp;private Set<ProductAisle> productAisle = new HashSet<>;&nbsp; &nbsp;/* getters, setters, equals and hashcode */}@Entity&nbsp;public class Aisle{&nbsp; &nbsp;@Id&nbsp; &nbsp;private Long id;&nbsp; &nbsp;private String row;&nbsp; &nbsp;private String shelf;&nbsp; &nbsp;@OneToMany(mappedBy = "aisle")&nbsp; &nbsp;private Set<ProductAisle> productAisle = new HashSet<>();&nbsp; &nbsp;/* getters, setters, equals and hashcode */}@Entity&nbsp;public class ProductAisle{&nbsp; &nbsp;@Id&nbsp; &nbsp;private Long id;&nbsp; &nbsp;@ManyToOne(fetch = FetchType.LAZY)&nbsp; &nbsp;private Product product;&nbsp; &nbsp;@ManyToOne(fetch = FetchType.LAZY)&nbsp; &nbsp;private Aisle aisle;&nbsp; &nbsp;/* getters, setters, equals and hashcode */}然后您Salesman将指向一组ProductAisle实例，这些实例将产品与通道映射：@Entity&nbsp;public class Salesman{&nbsp; &nbsp;@Id&nbsp; &nbsp;private Long id;&nbsp; &nbsp;private String name;&nbsp; &nbsp;@ManyToOne(fetch = FetchType.LAZY)&nbsp; &nbsp;private Set<ProductAisle> productAisle;}

Answer 2

由于两者Aisle和 相互之间Product具有双向映射，因此您可以将它们中的任何一个（甚至它们两个）加入到Salesman类中，而您根本不需要加入服务表。