如何使用Spring Data JPA查询没有主键的表

Question

have a simple query that I need to only run a select on. Below is the example select statement.

    <named-native-query name="Capacity.findByCapacityCount" result-class="com.model.Capacity">
        <query>    
SELECT MAX_VAL,
      FROM PARAMETER
     WHERE  LOCATION = :facilityCode
       AND FUN_C = :functionName
       AND PAM_TYP = :dayOfWeek
        </query>
    </named-native-query>

For the query results I created a simple Entity class called Capacity.

@Entity 
@Getter
@Setter
@NoArgsConstructor(access = AccessLevel.PROTECTED)
public class Capacity  {        

    @Column(name="PAM_VAL_DCM") 
    private BigDecimal slotCount;

}

When my application starts up I get an error with "No identifier specified for entity". I understated that Entity requires a Id property to be defined but in this case the table doesn't have a true primary key.

I have also tried changing the class to a @Embedable type but I get a the following error "Errors in named queries"

Below is the interface I have created using Repository interface.

public interface CapacityRepository extends Repository<Capacity,String> {

    public Capacity findByCapacityCount(@Param("facilityCode")String facilityCode,
                                                                                   @Param("functionName")String functionName,
                                                                                   @Param("dayOfWeek")String dayOfWeek);
}

So using Spring Data JPA how would configure a class using JPA annotations and the Repository interface to query a table without a primary key?

Answer 1

I don't think this is going to work but that's not due to Spring Data JPA's limitations but JPA not allowing entities without primary keys. See section 2.4 of the JPA specification.