How to update a single Property of an Object in Database with Post and NOT PATCH? (Java, springboot)

Question

I want to create a Post method to update a single property from my API main Object:

@Builder
@Document(collection = "tableItems")
@NoArgsConstructor
@AllArgsConstructor
@Data
public class TableItem {

    @Id
    private String id;
    private int roundNumber;
    private RoundState roundState;
    private int bigBlind;
    private int smallBlind;
    private int maxSize;
    private int freeSeats;
    private double tableChips;
    private List<Card> tableCards;
    private List<Player> players;
    private List<Seat> seats;

}

So, this object ist save on my MongoDB. I want to add a new Player on players, but all other properties should not change!

In my GameController, I have a @RequestMapping("/api/tableitems") and my method looks like this:

@PostMapping("/{id}/players")
public void postNewPlayer(@RequestBody Player newPlayer, String tableId) {
    gameService.addNewPlayer(id, newPlayer);
}

In my GameService my addNewPlayer method looks like this:

public void addNewPlayer(Player newPlayer, String tableId) {

    TableItem tableToBeUpdated = tableItemsRepo.findById(tableId)
            .orElseThrow( () -> new NoSuchElementException(("Table with ID " + tableId + " not found!")));

    tableItemsRepo.save(newPlayer);
}

IntelliJ grumbles and throws the following error message:

Inferred type 'S' for type parameter 'S' is not within its bound; should extend 'backend.model.TableItem'

And finally my repository looks like this:

@Repository
public interface TableItemsRepository extends MongoRepository<TableItem, String> {
}

Is it at all possible to update a single property of an object with @POST? How does it work? If not, how else can it be done? I am at a loss and would be very grateful for some help... Thanks a lot!

The HTTP mapping used on your controller has nothing to do with updating your entity. If you can somehow get it to your service with a GET request to your controller the service layer wouldn't care. — void void
– void void, Commented Jun 9, 2022 at 0:06
Hi, Thank you! I also noticed that my repo was expecting TableItem and I sent Player to it... — vangoh
– vangoh, Commented Jun 9, 2022 at 18:47

Alexandru Borza · Accepted Answer · 2022-06-09 06:56:51Z

0

you can have 2 solutions:

to use a DTO (Data Transfer Object). Get a DTO in controller, create a mapper from DTO to Entity and from Entity to DTO and create a function to update the Entity from the DTO. You can see more here: https://mapstruct.org/documentation/stable/reference/html/#updating-bean-instances
second solution, that I think that is easier to implement, it's to create a function that copy the properties of a entity to another and exclude the null ones. You can get more info here: How to ignore null values using springframework BeanUtils copyProperties?

answered Jun 9, 2022 at 6:56

Alexandru Borza

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Comments

vangoh · Accepted Answer · 2022-06-09 19:25:33Z

Thanks for the quick feedback! I have seen some thinking errors already... my Repository expects TableItems and I just give it the property I want to change(Player in Players). I also forgot by the @Post the PathVariable with the TableId.

Through your tips I have now found a solution that also works! Here my code:

Controller:

 @PostMapping("/{id}/players")
public void postNewPlayer(@RequestBody Player newPlayer, @PathVariable String id) {
    gameService.addNewPlayer(newPlayer, id);
}

Service:

public void addNewPlayer(Player newPlayer, String tableId) {

    TableItem tableToBeUpdated = tableItemsRepo.findById(tableId)
            .orElseThrow( () -> new NoSuchElementException(("Table with ID " + tableId + " not found!")));
    List<Player> players =  tableToBeUpdated.getPlayers();
    if( players == null) {
        players = new ArrayList<>();
        tableToBeUpdated.setPlayers(players);
    }
    players.add(newPlayer);
    tableItemsRepo.save(tableToBeUpdated);
}

I did not have to change anything in the repo. The result it looks like this in the DB:

{
   "roundNumber": 2,
   "bigBlind": 20,
   "smallBlind": 10,
   "maxSize": 2,
   "freeSeats": 2,
   "tableChips": 0,
   "tableCards": [
   {
      "rank": "FIVE",
      "suit": "HEARTS"
  },
  {
     "rank": "SEVEN",
     "suit": "SPADES"
  }
  ],
  "players": [
  {
     "playerName": "brasuca",
     "playerChips": 1000,
     "playerCards": [
     {
        "rank": "SEVEN",
        "suit": "HEARTS"
    },
    {
       "rank": "KING",
       "suit": "HEARTS"
    }
  ]
}
]}

Thank you very much for your help!!

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