根据您的错误，您Optional<RoomEntity>从存储库的findAll方法获取数据并将其转换为RoomEntity。
而不是RoomEntity roomEntity = roomrepository.findById(roomId);这样做
Optional<RoomEntity> optinalEntity = roomrepository.findById(roomId);RoomEntity roomEntity = optionalEntity.get();
解决方法我目前正在使用Spring创建一个网站，但偶然发现了这种基本情况，我对如何解决此特定代码一无所知：Entity = Optional;
RoomEntity roomEntity = roomRepository.findById(roomId);
ReservationResource（API请求类）：
public class ReservationResource { @Autowired RoomRepository roomRepository; @RequestMapping(path = '/{roomId}',method = RequestMethod.GET,produces = MediaType.APPLICATION_JSON_UTF8_VALUE) public ResponseEntity<RoomEntity> getRoomById( @PathVariable Long roomId){RoomEntity roomEntity = roomRepository.findById(roomId);return new ResponseEntity<>(roomEntity,HttpStatus.OK);} }}
RoomRepository类：
public interface RoomRepository extends CrudRepository<RoomEntity,Long> { List<RoomEntity> findAllById(Long id);}
房间实体
@Entity@Table(name = 'Room')public class RoomEntity { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @NotNull private Integer roomNumber; @NotNull private String price; public RoomEntity() {super(); }}
