Spring Boot. how to Pass Optional<> to an Entity Class

Question

i am currently making a website using spring and i stumble upon this basic scenario that i don\'t have any idea on how to solve this specific code: Entity = Optional;

Answer 1

First solution

You can implement JpaRepository instead of CrudRepository which provide a getOne method that returns an RoomEntity as you expect. (JpaRepository for JPA or MongoRepository for MongoDB) :

public interface RoomRepository extends JpaRepository {
    List findAllById(Long id);
}

and

RoomEntity roomEntity = roomRepository.getOne(roomId);

Note that an EntityNotFoundException will be thrown if there's no RoomEntity for this roomId.

Second solution

The findById method of CrudRepository returns an optional so you must deal with it properly to get an RoomEntity if there is one. For example :

RoomEntity roomEntity = optionalEntity.roomRepository.findById(roomId).get();

In this case .get() will throw a NoSuchElementException if there's no RoomEntity for this roomId.

This article may help to understand optionals : http://www.baeldung.com/java-optional