Spring JPA Two Entities for same DB table-CodePudding

I am writing Spring Boot Data JPA application and I have following situation:

I have 2 database queries fetching from same table but they are fetching different columns and data based on their WHERE clauses. For example:

SELECT CAR_TYPE, CAR_MODEL, CAR_YEAR, ACCIDENT_YEAR, BUY_DAY FROM CAR WHERE ACCIDENT_YEAR IS NULL

, and

SELECT CAR_MODEL, CAR_YEAR FROM CAR WHERE CAR_YEAR >= CURRENT_YEAR

As you can see these 2 queries (whose results will be exposed through 2 different API points) reference the same table CAR, but return different fields and have different WHERE clauses.

I know in JPA, I have to create an entity CarEntity like:

@Entity
@Table(name = "CAR")
public class CarEntity {
   // I can only have fields from one or the other query 
   // here, so I guess I have to have 2 of these
}

, but my problem is that this entity needs to apply for the 2 different queries (with different fields returned, different data, different WHERE clauses).

So, it looks like I have to have actually 2 CarEntity classes. But, I am not sure how to make these 2 CarEntities so they both reference the same table CAR?

CodePudding user response：

You can do by using projection that basically you define an interface with field methods which you want to get them. Projections

@Entity
public class Car implement CarSummary { // if you want you can implement JIC
  
  private UUID id;
  private String carType;
  private String carModel;
  private LocalDateTime carYear;
  
  //getters and setters

}


public interface CarSummary {

  String getCardModel();
  String getCarYear();

}

Then on your query.

public interface CarRepository extends Repository<Car, UUID> {
  Collection<CarSummary> findByCarYearGreaterThan(LocalDateTime now);
  Collection<Car> findByAccidentYearIsNull();
}