One method to save entity which extand abstract class in repository

Question

I am new at abstract class as Entity so for training I created abstract class

@Entity
@Inheritance(strategy = TABLE_PER_CLASS)
@Getter
@Setter
@NoArgsConstructor
public abstract class ShapeEntity {
     @Id
     @GeneratedValue(generator = "system-uuid")
     @GenericGenerator(name = "system-uuid", strategy = "uuid")
     private String id = UUID.randomUUID().toString();
}

and classes which extand Shape:

public class SquareEntity extends ShapeEntity {
    ...
}
public class CircleEntity extends ShapeEntity {
    ...
}

every entity has repostiory like that:

public interface CircleEntityRepository extends JpaRepository<CircleEntity, String> {
}

When I want to update entity I am searching it in every repository, next (if entity was found) map parameters and finnaly have to save that entity in database. How can I easy decide which repository should be used for it? I created method save with if else which now works:

public ShapeEntity save(ShapeEntity shapeEntity) {
    if (shapeEntity.getClass().getName().contains("CircleEntity")) {
        return circleEntityRepository.save((CircleEntity) shapeEntity);
    } else if (shapeEntity.getClass().getName().contains("SquareEntity")) {
        return squareEntityRepository.save((SquareEntity) shapeEntity);
    } else {
        throw new EntityNotFoundException();
    }
}

but it is a bit uncomfortable becouse when I will have 20 entities I will have to create 20 else if loops. Can I do any interface for this or something like that?

score 1 · Accepted Answer · answered Sep 22 '22 at 10:08

If you create a ShapeEntityRepository for the ShapeEntity class you don't need if-else blocks.

public interface ShapeEntityRepository
        extends JpaRepository<ShapeEntity, String>, 
        JpaSpecificationExecutor<ShapeEntity> {}

ShapeEntityRepository is useable for all classes that are extended from the ShapeEntity class.

ShapeEntity circleEntity = new CircleEntity();
ShapeEntity squareEntity = new SquareEntity();

shapeEntityRepository.save(circleEntity);
shapeEntityRepository.save(squareEntity);

Alternatively, if there must be different repositories, you can use Spring's GenericTypeResolver to get the repository of the class.

@Component
public class RepositoryHolder {

    private final List<JpaRepository> jpaRepositories;

    public RepositoryHolder(List<JpaRepository> jpaRepositories) {
        this.jpaRepositories = jpaRepositories;
    }

    public JpaRepository getRepositoryBy(Class<?> domainClass) {
        Optional<JpaRepository> optionalRepository = jpaRepositories.stream()
                .filter(repository -> GenericTypeResolver
                        .resolveTypeArguments(
                                repository.getClass(),
                                Repository.class
                        )[0]
                        .equals(domainClass))
                .findFirst();
        if (optionalRepository.isPresent()) {
            return optionalRepository.get();
        } else throw new IllegalArgumentException();
    }
}

If you want to use it, your save(...) method will be something like this:

public void save(ShapeEntity shapeEntity) {
    JpaRepository repository = repositoryHolder
            .getRepositoryBy(shapeEntity.getClass());
    repository.save(shapeEntity);
}

Note: JPA Repository allows to use default CRUD functions, you can add an intermediate repository bean like here and reduce these codes to that intermediate repository.

One method to save entity which extand abstract class in repository

1 Answers1