hibernate - 我如何让许多 @ManyToMany 关系起作用？

Question

我有一个具有两个多对多关系的模型。 Play 框架为我创建了关系表，但没有一个 id 可以为空，导致我无法让我的代码工作。

Play 框架返回
PersistenceException 发生:插入 Costumer_Item (customersWhoIgnored_id, ignoreItems_id) 值 (?, ?)

19:20:54,530 ERROR ~ Field 'customersWhoBought_id' doesn't have a default value
19:20:54,531 ERROR ~ Could not synchronize database state with session
org.hibernate.exception.GenericJDBCException: Could not execute JDBC batch update

代码是Item.java:

@Entity
public class Item extends Model {
  @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "ownedItems")
  public List<Costumer> customersWhoBought;

  @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "ignoredItems")
  public List<Costumer> customersWhoIgnored;
}

客户.java:

@Entity
public class Customer extends Model {
  @Column(nullable = true)
  @ManyToMany(cascade = CascadeType.ALL)
  public List<Item> ownedItems;

  @Column(nullable = true)
  @ManyToMany(cascade = CascadeType.ALL)
  public List<Item> ignoredItems;

}

我如何让许多 @ManyToMany 关系起作用？

Answer 1

我认为两个关系都使用相同的连接表，默认名称为 Costumer_Item ，导致困惑。您需要手动指定不同的名称:

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "CostumerToOwnedItems")
public List<Item> ownedItems;

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "CostumerToIgnoredItems")
public List<Item> ignoredItems;