覆蓋JPA MappedSuperClass通用屬性

Question

我有下面的場景，我需要子類能夠指定在MappedSuperClass（s​​）中找到的屬性的實際類型。我使用hibernate作爲提供程序，我不介意使用hibernate特定的註釋來解決此問題。

@MappedSuperclass 
abstract class BaseA{ 
    .... 

    @OneToMany(mappedBy = "baseA") 
    public Set<? extends BaseB> getBaseB(){ 
     ..... 
    } 
} 

@MappedSuperclass 
abstract class BaseB{ 
    ..... 

    @ManyToOne(optional = false) 
    @JoinColumn(name = "basea_id") 
    public BaseA getBaseA(){ 
     ..... 
    } 
} 

@Entity 
class BaseAImpl extends BaseA{ 
    public Set<BaseBImpl> getBaseB(){ 
     ..... 
    } 
} 

@Entity  
class BaseBImpl{ 

    public BaseAImpl getBaseA(){ 
     ..... 
    } 
} 

Answer 1

@AssociationOverride在這種情況下將hep你。請參閱documentation（當然，這是一個JPA註釋）。您可以將它與@AttributeOverrides註釋結合使用以覆蓋基本類型。示例（取自示例）：

@MappedSuperclass 
public class Employee { 
    ... 
    @ManyToOne 
    protected Address address; 
    ... 
} 

@Entity 
@AssociationOverride(name="address", 
         joinColumns=@JoinColumn(name="ADDR_ID")) 
    // address field mapping overridden to ADDR_ID foreign key 
public class PartTimeEmployee extends Employee { 
    ... 
}