@Override
    public void save(User user) {
        Integer id = user.getId();
        String username = user.getUsername();
        String password = user.getPassword();
        try (Statement stmt = connection.createStatement()){
            stmt.execute("INSERT INTO shop_user(id, username, password) VALUES (" + id + ", '" + username + "', '" + password + "')");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }