Create a handler for your command

The command itself contains only information that the handler needs to do something with it.

You can create a handler by implementing the CommandHandler interface, which looks like this

src/core/handlers/CreateUserCommandHandler.java

@Component
class CreateUserCommandHandler implements CommandHandler<CreateUserCommand, User> {

    @Override
    public CommandResult<User> execute(CreateUserCommand command) {
        return CommandResult.of(new User(command.username));
    }
}

The CommandHandler interface has two generic parameters, where the first one is the command class itself, and the second is the command result which will be returned inside the CommandResult class.