Issue
I would like to ask you for some best practice to reduce the amount of repeatable code in my controller's methods - one of them is presented below.
I have quite a big and complex view with a lot of information and two forms. In every method of my controller (and there are quite a few) I have to pass the same attributes to my view (in post controllers even twice). I added a note SAME CODE in the code snippet below indicating identical pieces of code.
I wonder if there is any possibility to make a one global method in the controller gathering all attributes to be passed to the model and just reference it in any of particular methods?
I looked into ModelAndView or ModelMap, but cannot see those being suitable here.
Just want to avoid repeating this part:
Repeatable piece of code
model.addAttribute("hotels", hotelService.getAllHotels());
List<GetRoomDto> roomsDto = roomService.getAllRoomsByHotelId(hotelId);
model.addAttribute("rooms", roomsDto);
model.addAttribute("roomTypes", roomTypeService.findAllRoomTypeNames());
Full method with that piece of code appearing twice
@PostMapping("/hotels/{hotelId}/rooms")
public String createRoomForHotelById(@ModelAttribute("room") @Valid NewRoomDto roomDto,
BindingResult result,
@PathVariable("hotelId") Long hotelId,
Model model) {
if(result.hasErrors()) {
// SAME CODE
model.addAttribute("hotels", hotelService.getAllHotels());
List<GetRoomDto> roomsDto = roomService.getAllRoomsByHotelId(hotelId);
model.addAttribute("rooms", roomsDto);
model.addAttribute("roomTypes", roomTypeService.findAllRoomTypeNames());
//
model.addAttribute("hotel", new NewHotelDto());
LOG.info("Binding error: {}", result.toString());
return "admin/dashboard";
}
// SAME CODE
model.addAttribute("hotels", hotelService.getAllHotels());
List<GetRoomDto> roomsDto = roomService.getAllRoomsByHotelId(hotelId);
model.addAttribute("rooms", roomsDto);
model.addAttribute("roomTypes", roomTypeService.findAllRoomTypeNames());
//
LOG.info("AdminController: CreateRoomForHotelById: Created room: {}", roomDto.toString());
roomDto.setHotelId(hotelId);
roomService.createNewRoom(roomDto);
return "redirect:/auth/admin/hotels/{hotelId}/rooms";
}
Solution
You can also move the code from J Asgarov's answer into the same controller instead of another class annotated with @ControllerAdvice
. That way that code will only be executed for @RequestMapping
methods within that controller.
For multiple values you could also do something like this:
@ModelAttribute
public void foo(Model model, @PathVariable(required = false) Long hotelId) {
model.addAttribute("hotels", hotelService.getAllHotels());
if (hotelId != null) {
List<GetRoomDto> roomsDto = roomService.getAllRoomsByHotelId(hotelId);
model.addAttribute("rooms", roomsDto);
}
model.addAttribute("roomTypes", roomTypeService.findAllRoomTypeNames());
}
But seeing your code I would rather suggest you move the repeated code into a private method and call it whenever you need those inside your model.
Your method createRoomForHotelById
for example causes a redirect, which basically discards everything you put in your model.
Answered By - Ken S
Answer Checked By - Terry (JavaFixing Volunteer)