diff -r fd8c40ff78c3 -r 824d4042c857 src/main/java/de/uapcore/lightpit/dao/UserDao.java
--- a/src/main/java/de/uapcore/lightpit/dao/UserDao.java	Sat May 09 15:19:21 2020 +0200
+++ b/src/main/java/de/uapcore/lightpit/dao/UserDao.java	Sat May 09 17:01:29 2020 +0200
@@ -1,8 +1,8 @@
 /*
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
- * 
+ *
  * Copyright 2018 Mike Becker. All rights reserved.
- * 
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
@@ -30,50 +30,6 @@
 
 import de.uapcore.lightpit.entities.User;
 
-import java.sql.Connection;
-import java.sql.ResultSet;
-import java.sql.SQLException;
-import java.sql.Statement;
-import java.util.ArrayList;
-import java.util.List;
-
-public class UserDao {
-
-    /**
-     * Maps SQL columns to POJO fields.
-     *
-     * @param result the database result set
-     * @param user   the POJO
-     * @throws SQLException on any kind of SQL errors
-     */
-    protected void mapColumns(ResultSet result, User user) throws SQLException {
-        user.setUserID(result.getInt("userid"));
-        user.setUsername(result.getString("username"));
-        user.setGivenname(result.getString("givenname"));
-        user.setLastname(result.getString("lastname"));
-    }
+public interface UserDao extends GenericDao<User> {
 
-    /**
-     * Returns a list of all users ordered by their username.
-     * <p>
-     * Does not return reserved system users with negative user IDs.
-     *
-     * @param conn the connection to use
-     * @return a list of all users
-     * @throws SQLException on any kind of SQL errors
-     */
-    public List<User> listAll(Connection conn) throws SQLException {
-        List<User> list = new ArrayList<>();
-        try (
-                Statement stmt = conn.createStatement();
-                ResultSet result = stmt.executeQuery(
-                        "SELECT * FROM lpitcore_user WHERE userid >= 0 ORDER BY username")) {
-            while (result.next()) {
-                final User user = new User();
-                mapColumns(result, user);
-                list.add(user);
-            }
-        }
-        return list;
-    }
 }