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Endpoint

Changes the name of an existing player. The new name must be valid and follow validation constraints.

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Path Parameters

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playerId
string
required
The unique identifier (UUID) of the player whose name you want to change

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Request Body

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newName
string
required
The new name for the player. Must be between 1-30 characters (after trimming whitespace) and not blank.

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Validation Rules

The player name must satisfy the following constraints:
The name cannot be empty or consist only of whitespace. Leading and trailing whitespace is automatically trimmed.
PlayerName.java
if (v.isEmpty()) throw new IllegalArgumentException("PlayerName cannot be blank");
After trimming whitespace, the name must not exceed 30 characters.
PlayerName.java
if (v.length() > 30) throw new IllegalArgumentException("PlayerName too long (max 30)");
Leading and trailing whitespace is automatically removed from the name.
PlayerName.java
String v = value.trim();

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Response

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playerId
string
The unique identifier of the player
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name
string
The player’s new name (after trimming)
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wins
int
Number of games won by the player
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losses
int
Number of games lost by the player

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Examples

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Successful Name Change

curl -X PUT http://localhost:8080/player/7c9e6679-7425-40de-944b-e07fc1f90ae7 \
  -H "Content-Type: application/json" \
  -d '{"newName": "Alice Supreme"}'

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Trimming Whitespace

curl -X PUT http://localhost:8080/player/7c9e6679-7425-40de-944b-e07fc1f90ae7 \
  -H "Content-Type: application/json" \
  -d '{"newName": "  Bob  "}'

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Error Responses

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400 Bad Request - Blank Name

curl -X PUT http://localhost:8080/player/7c9e6679-7425-40de-944b-e07fc1f90ae7 \
  -H "Content-Type: application/json" \
  -d '{"newName": "   "}'

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400 Bad Request - Name Too Long

curl -X PUT http://localhost:8080/player/7c9e6679-7425-40de-944b-e07fc1f90ae7 \
  -H "Content-Type: application/json" \
  -d '{"newName": "This name is definitely way too long for a player"}'

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404 Not Found - Player Doesn’t Exist

curl -X PUT http://localhost:8080/player/00000000-0000-0000-0000-000000000000 \
  -H "Content-Type: application/json" \
  -d '{"newName": "Alice"}'

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Implementation Details

The endpoint follows a clean architecture pattern with domain-driven design:
1

Validate Request

The request is validated at the controller level using Jakarta Bean Validation annotations:
ChangePlayerNameRequest.java
public record ChangePlayerNameRequest(
    @NotBlank(message = "Player name must not be blank") 
    @Size(max = 30, message = "Player name length must be <= 30") 
    String newName
) {}
2

Create Domain Object

The use case creates a PlayerName value object, which performs domain-level validation:
ChangePlayerNameUseCase.java
try {
    newName = new PlayerName(cmd.newName());
} catch (IllegalArgumentException e) {
    return Mono.error(new InvalidPlayerNameException(e.getMessage()));
}
3

Retrieve Player

The player is retrieved from the repository:
return playerRepo.findById(pId)
    .switchIfEmpty(Mono.error(new PlayerNotFoundException(cmd.playerId())))
4

Apply Rename

The immutable rename() method returns a new player instance:
.map(player -> player.rename(newName))
5

Persist and Return

The updated player is saved and returned as a DTO:
.flatMap(playerRepo::save)
.map(this::toResult);
The Player aggregate is immutable, so the rename() method returns a new Player instance rather than modifying the existing one.

Player Overview

Learn about the Player aggregate

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