package com.baeldung.javalin.User; import io.javalin.Handler; import java.util.Objects; public class UserController { public static Handler fetchAllUsernames = ctx -> { UserDao dao = UserDao.instance(); Iterable allUsers = dao.getAllUsernames(); ctx.json(allUsers); }; public static Handler fetchById = ctx -> { int id = Integer.parseInt(Objects.requireNonNull(ctx.param("id"))); UserDao dao = UserDao.instance(); User user = dao.getUserById(id).get(); if (user == null) { ctx.html("Not Found"); } else { ctx.json(user); } }; }