java - 需要帮助来解决连接表问题

Question

我有如下两张表，问题是每本书只能由一个人拥有。

Person_ID Book_ID
1           1          <<correct
2           1          << ERORR

如何改变它以使每本书可以被很多人拥有？

人.java

@Entity
public class Person {
  private long id;
  .....
  @OneToMany(cascade = CascadeType.ALL)
  public Set<Book> getBooks() {
        return books;
  }
 ....
}

图书.java

@Entity
public class Book {
 private long id;
 ....
}

Answer 1

您需要将关系更改为 ManyToMany

Answer 2

您可以使用注释@ManyToMany

@Entity
 public class Person {
 private long id;
.....
 @ManyToMany(cascade = CascadeType.ALL)
 public Set<Book> getBooks() {
      return books;
   }
 ....
  }