How to intercept a login request?

#Answer

To intercept a login request, let's create a LoginRequestHandler class, verify Login information and throw BadRequestException if it's invalid, example:

@Data
@ServerEventHandler(event = ServerEvent.USER_LOGIN)
public class UserLoginHandler {

    @RequestParam("1") private String version;
    
    public void handle(AppContext context, String username, String password) throws Exception {
        context.command(Log.class).info("user {} login with password = {}, on version = {}", 
                username, password, version);
        if(StringUtils.isEmpty(version))
            throw new BadRequestException("Invalid version", 3); // error code = 3
    }
}