diff -r 4f912cd42876 -r 86b5d8a1662f src/main/java/de/uapcore/lightpit/dao/postgres/PGUserDao.java
--- a/src/main/java/de/uapcore/lightpit/dao/postgres/PGUserDao.java	Fri Nov 06 10:50:32 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,132 +0,0 @@
-/*
- * 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:
- *
- *   1. Redistributions of source code must retain the above copyright
- *      notice, this list of conditions and the following disclaimer.
- *
- *   2. Redistributions in binary form must reproduce the above copyright
- *      notice, this list of conditions and the following disclaimer in the
- *      documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- */
-package de.uapcore.lightpit.dao.postgres;
-
-import de.uapcore.lightpit.dao.UserDao;
-import de.uapcore.lightpit.entities.User;
-
-import java.sql.Connection;
-import java.sql.PreparedStatement;
-import java.sql.ResultSet;
-import java.sql.SQLException;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Objects;
-import java.util.Optional;
-
-import static de.uapcore.lightpit.dao.Functions.getSafeString;
-import static de.uapcore.lightpit.dao.Functions.setStringOrNull;
-
-public final class PGUserDao implements UserDao {
-
-    private final PreparedStatement insert, update, list, find, findByUsername;
-
-    public PGUserDao(Connection connection) throws SQLException {
-        list = connection.prepareStatement(
-                "select userid, username, lastname, givenname, mail " +
-                        "from lpit_user where userid >= 0 " +
-                        "order by username");
-        find = connection.prepareStatement(
-                "select userid, username, lastname, givenname, mail " +
-                        "from lpit_user where userid = ? ");
-
-        findByUsername = connection.prepareStatement(
-                "select userid, username, lastname, givenname, mail " +
-                        "from lpit_user where lower(username) = lower(?) ");
-
-        insert = connection.prepareStatement("insert into lpit_user (username, lastname, givenname, mail) values (?, ?, ?, ?)");
-        update = connection.prepareStatement("update lpit_user set lastname = ?, givenname = ?, mail = ? where userid = ?");
-    }
-
-    static User mapColumns(ResultSet result) throws SQLException {
-        final int id = result.getInt("userid");
-        if (id == 0) return null;
-        final var user = new User(id);
-        user.setUsername(result.getString("username"));
-        user.setGivenname(getSafeString(result, "givenname"));
-        user.setLastname(getSafeString(result, "lastname"));
-        user.setMail(getSafeString(result, "mail"));
-        return user;
-    }
-
-    @Override
-    public void save(User instance) throws SQLException {
-        Objects.requireNonNull(instance.getUsername());
-        insert.setString(1, instance.getUsername());
-        setStringOrNull(insert, 2, instance.getLastname());
-        setStringOrNull(insert, 3, instance.getGivenname());
-        setStringOrNull(insert, 4, instance.getMail());
-        insert.executeUpdate();
-    }
-
-    @Override
-    public boolean update(User instance) throws SQLException {
-        if (instance.getId() < 0) return false;
-        setStringOrNull(update, 1, instance.getLastname());
-        setStringOrNull(update, 2, instance.getGivenname());
-        setStringOrNull(update, 3, instance.getMail());
-        update.setInt(4, instance.getId());
-        return update.executeUpdate() > 0;
-    }
-
-    @Override
-    public List<User> list() throws SQLException {
-        List<User> users = new ArrayList<>();
-        try (var result = list.executeQuery()) {
-            while (result.next()) {
-                users.add(mapColumns(result));
-            }
-        }
-        return users;
-    }
-
-    @Override
-    public User find(int id) throws SQLException {
-        find.setInt(1, id);
-        try (var result = find.executeQuery()) {
-            if (result.next()) {
-                return mapColumns(result);
-            } else {
-                return null;
-            }
-        }
-    }
-
-    @Override
-    public Optional<User> findByUsername(String username) throws SQLException {
-        findByUsername.setString(1, username);
-        try (var result = findByUsername.executeQuery()) {
-            if (result.next()) {
-                return Optional.of(mapColumns(result));
-            } else {
-                return Optional.empty();
-            }
-        }
-    }
-}