java - ElementCollection/MappedSuperclass/AssociationOverride 的问题

Question

我无法覆盖关联。阅读 javadoc http://download.oracle.com/javaee/6/api/javax/persistence/CollectionTable.html你可以阅读“另见:ElementCollection、AttributeOverride、AssociationOverride、Column”，这让我们假设您可以使用它，但我不知道这怎么行不通。

@MappedSuperclass
public class AbstractUser {
 [...]
public String getLastname() { ...}
    @ElementCollection
    @CollectionTable(joinColumns=@JoinColumn(name="user_id"))
    @Column(name="nickname")
    public Set<String> getNicknames() { ... } 

实现

@Entity
@Table(name="users")
@Table(name="user_rfcs")
@AssociationOverride(name = "nicknames",
        joinTable = @JoinTable(name = "user_nicknames", joinColumns = @JoinColumn(name = "user_id"))
)
public class User extends AbstractUser {
[...]
}



@Entity
@Table(name="user_rfcs")
@AssociationOverride(name = "nicknames",
        joinTable = @JoinTable(name = "user_rfc_nicknames", joinColumns = @JoinColumn(name = "user_id"))
)
public class UserRFC extends AbstractUser  {
       [...]
}

Answer 1

@AssociationOverride 由于以下原因在“另见”部分中提到:

If the embeddable class contains references to other entities, the default values for the columns corresponding to those references may be overridden by means of the AssociationOverride and/or AssociationOverrides annotations.

从另一方面来看，@AssociationOverride 的 javadoc 说它只能应用于实体关系，而不是基元集合:

Used to override a mapping for an entity relationship

所以，看起来你不能用 @AssociationOverride 来完成它，你必须在子类中用不同的注释覆盖 getNicknames() 方法。