How to show data from table that is mapped with another table in Many To One relationship full stack using Spring boot (backend) and Thymeleaf (front) - spring

Question

This is full-stack project based on Spring Boot (backend) and Thymeleaf (frontend). I have this page (table) on my website which shows all hotels in my Hotel Management System App:
When I click on Details it shows new page for particular hotel:
When I click on View Rooms it should show the list of the rooms available for that particular Hotel. I wonder how can I do that? So far, I was only available to list all the rooms (not related to particular hotel) but I want to list the rooms for the particular hotel only.
class Room is mapped with class Hotel by #ManyToOne relationship, which means that several rooms can be listed in one hotel (I will show souce code bellow). When I want to create new room, there is an option to choose to which hotel that particular room belongs:
Here is the code of classes Room and Hotel :
#Entity
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
#ToString
#Builder
#Table(
name = "room"
)
public class Room {
#Id
#SequenceGenerator(
name = "room_sequence",
sequenceName = "room_sequence",
allocationSize = 1
)
#GeneratedValue(
strategy = GenerationType.SEQUENCE,
generator = "room_sequence"
)
private Long roomId;
#Column(
name = "name",
nullable = false
)
private String name;
#Column(
name = "price"
)
private Integer price;
#ManyToOne
#JoinColumn(
name = "hotel_id",
referencedColumnName = "hotelId"
)
private Hotel hotel;
}
#Entity
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
#ToString
#Builder
#Table(
name = "hotel"
)
public class Hotel {
#Id
#SequenceGenerator(
name = "hotel_sequence",
sequenceName = "hotel_sequence",
allocationSize = 1
)
#GeneratedValue(
strategy = GenerationType.SEQUENCE,
generator = "hotel_sequence"
)
private Long hotelId;
#Column(
name = "name",
nullable = false
)
private String name;
#Column(
name = "star",
nullable = false
)
private Integer star;
#Column(
name = "location",
nullable = false
)
private String location;
#JsonIgnore
#OneToMany(mappedBy = "hotel")
#ToString.Exclude
private Set<Room> rooms;
}
And here is the whole RoomController with methods to: create new room, update existing room, delete room, show "create new room" form, show "update existing room" form etc.:
#Controller
#RequestMapping("/hms/rooms")
public class RoomController {
private final RoomServiceImpl roomService;
private final HotelServiceImpl hotelService;
#Autowired
public RoomController(RoomServiceImpl roomService, HotelServiceImpl hotelService) {
this.roomService = roomService;
this.hotelService = hotelService;
}
#GetMapping
public String listRooms(Model model) {
model.addAttribute("rooms", roomService.getAllRooms());
return "rooms";
}
#GetMapping("/new")
public String addRoomForm(Model model) {
Room room = new Room();
List<Hotel> listHotels = hotelService.getAllHotels();
model.addAttribute("room", room);
model.addAttribute("listHotels", listHotels);
return "room_create";
}
#PostMapping
public String addNewRoom(#ModelAttribute("room") Room room) {
roomService.addNewRoom(room);
return "redirect:/hms/rooms";
}
#GetMapping("/edit/{roomId}")
public String updateRoomForm(#PathVariable Long roomId, Model model) {
List<Hotel> listHotels = hotelService.getAllHotels();
model.addAttribute("room", roomService.findRoomById(roomId));
model.addAttribute("listHotels", listHotels);
return "room_edit";
}
#PostMapping("/{roomId}")
public String updateRoom(#PathVariable Long roomId, #ModelAttribute("room") Room room) {
// get room from database by id
Room existingRoom = roomService.findRoomById(roomId);
existingRoom.setRoomId(roomId);
existingRoom.setName(room.getName());
existingRoom.setPrice(room.getPrice());
existingRoom.setHotel(room.getHotel());
// save updated room object
roomService.updateRoom(existingRoom);
return "redirect:/hms/rooms";
}
// handler method to handle delete room request
#GetMapping("/{roomId}")
public String deleteRoom(#PathVariable Long roomId) {
roomService.deleteRoomById(roomId);
return "redirect:/hms/rooms";
}
#GetMapping("/details/{roomId}")
public String viewRoom(#PathVariable Long roomId, Model model) {
model.addAttribute("room", roomService.findRoomById(roomId));
return "room_view";
}
}
Also, here is the thymeleaf logic code which is used to get list of hotels on "create new room form":
<div class="form-group">
<label> Hotel </label>
<select th:field="*{hotel}" class="form-control" required>
<th:block th:each="hotel : ${listHotels}">
<option th:text="${hotel.name}" th:value="${hotel.hotelId}"/>
</th:block>
</select>
</div>

Answer 1

You could easily achieve at your repository level as well as in your thymleaf too, please have a look at code below
<span th:each="room : ${hotel.getRooms()}">
I hope it helps!