You can add following enumeration, to indicate you want the String representation to be persisted :
@Enumerated(EnumType.STRING)private ApartmentState apartmentState;
Use this annotation at field level:
@Enumerated(EnumType.STRING)
I also had to add
@Embeddable to the java enum
@Embeddable public enum ApartmentState { FREE, REQUESTED, BOOKED, LIVED, CLEANING, PROCESSING }