Write code once

In dit voorbeeld heb ik een stuk code gebruikt uit de UserDAO uit het vorige project. Daarin had ik 3 keer dezelfde code geschreven:

Methode: getTeachers


public List<User> getTeachers() {
        List<User> resultList = new ArrayList<>();
        String sql = "SELECT * FROM `User` WHERE role = ?;";
        try {
            setupPreparedStatement(sql);
            preparedStatement.setString(1, "Docent");
            ResultSet resultSet = preparedStatement.executeQuery();
            while (resultSet.next()) {
                User user = new User(resultSet.getInt("userId"),
                        resultSet.getString("userName"),
                        resultSet.getString("password"),
                        resultSet.getString("firstName"),
                        resultSet.getString("infix"),
                        resultSet.getString("surname"),
                        resultSet.getString("role"));
                resultList.add(user);
            }
        } catch (SQLException sqlError) {
            System.out.println(sqlError.getMessage());
        }
        return resultList;
    }

Methode: getOneById


@Override
    public User getOneById(int id) {
        User user = null;
        String sql = "Select * From User Where userId = ?;";
        try {
            setupPreparedStatement(sql);
            preparedStatement.setInt(1, id);
            ResultSet resultSet = executeSelectStatement();
            while (resultSet.next()) {
                user = new User(resultSet.getInt("userId"),
                        resultSet.getString("userName"),
                        resultSet.getString("password"),
                        resultSet.getString("firstName"),
                        resultSet.getString("infix"),
                        resultSet.getString("surname"),
                        resultSet.getString("role"));
            }
        } catch (SQLException foutmelding) {
            System.out.println(foutmelding.getMessage());
        }
        return user;
    }

Methode: getOneByName


 public User getOneByName(String name) {
        User user = null;
        String sql = "Select * From User Where userName = ?;";
        try {
            setupPreparedStatement(sql);
            preparedStatement.setString(1, name);
            ResultSet resultSet = executeSelectStatement();
            while (resultSet.next()) {
                user = new User(resultSet.getInt("userId"),
                        resultSet.getString("userName"),
                        resultSet.getString("password"),
                        resultSet.getString("firstName"),
                        resultSet.getString("infix"),
                        resultSet.getString("surname"),
                        resultSet.getString("role"));
            }
        } catch (SQLException foutmelding) {
            System.out.println(foutmelding.getMessage());
        }
        return user;
    }

Dat zou efficiënter kunnen door deze methodes te combineren in een methode:


private User createUserFromResultSet(ResultSet resultSet) throws SQLException {
    return new User(
        resultSet.getInt("userId"),
        resultSet.getString("userName"),
        resultSet.getString("password"),
        resultSet.getString("firstName"),
        resultSet.getString("infix"),
        resultSet.getString("surname"),
        resultSet.getString("role")
    );
}