public class MarkDao extends Dao<Mark> {
     
    Connection connection=null;
    ResultSet resultSet=null;
    PreparedStatement insert=null;
        PreparedStatement select=null;
        PreparedStatement delete=null;
        PreparedStatement update=null;
     
    private String url="jdbc:mysql://localhost:3306/student";
    private String password="root";
    private String user="root";
    public Connection getConnection() {
     
    try {
    Class.forName("com.mysql.jdbc.Driver");
    if(connection==null){
    connection= DriverManager.getConnection(url, password, user);
    }
    } catch (ClassNotFoundException e) {
    e.printStackTrace();
    } catch (SQLException e) {
    e.printStackTrace();
    }
    return connection;
    }
     
     
     
    @Override
    public void insert(Mark obj) {
    String sql="insert into mark ( student_id, discipline_id, mark) values (?,?,?);";
    try {
    insert=connection.prepareStatement(sql);
    insert.setInt(1, obj.getStudent_id());
    insert.setInt(2, obj.getDiscipline_id());
    insert.setInt(3, obj.getMark());
    insert.executeUpdate();
    } catch (SQLException e) {
    e.printStackTrace();
        closePreparedStatement();
    }
    }
     
    @Override
    public List<Mark> select() {
    List<Mark> marks=new LinkedList<>();
    String sql="select id, student_id, discipline_id, mark from mark" ;
    Mark mark=null;
    try {
    select=connection.prepareStatement(sql);
    resultSet=select.executeQuery();
    while(resultSet.next()){
    mark=new Mark();
    mark.setId(resultSet.getInt("id"));
     
    mark.setStudent_id(resultSet.getInt("student_id"));
    mark.setDiscipline_id(resultSet.getInt("discipline_id"));
    mark.setMark(resultSet.getInt("mark"));
    marks.add(mark);
    }
    } catch (SQLException e) {
    e.printStackTrace();
    }finally {
    if(resultSet!=null){
    try {
    resultSet.close();
    } catch (SQLException e) {
    e.printStackTrace();
    }
    }
    }
        closePreparedStatement();
    System.out.println(marks);
    return marks;
      
    }
     
    @Override
    public void delete(Mark obj, int id) {
    String sql="delete from mark where id=?;";
    try {
    delete=connection.prepareStatement(sql);
    delete.setInt(1, id);
    delete.executeUpdate();
     
    } catch (SQLException e) {
    e.printStackTrace();
    }
        closePreparedStatement();
    }
     
    @Override
    public void update(Mark obj) {
    String sql="Update mark set mark=? where id=?;";
    try {
    update=connection.prepareStatement(sql);
     
    update.setInt(1, obj.getId());
    update.executeUpdate();
    } catch (SQLException e) {
    e.printStackTrace();
    }
    closePreparedStatement();
    }
     
    public void closeConnection() {
    try {
    if (connection != null) {
    connection.close();
    }
    } catch (Exception e) {
     
    }
     
    }
     
        public void closePreparedStatement() {
            try{
                if (insert!=null ){
                    insert.close();
                }
            }catch (SQLException e){
                e.printStackTrace();
            }
            try{
                if (select!=null ){
                    select.close();
                }
            }catch (SQLException e){
                e.printStackTrace();
            }
            try{
                if (update!=null ){
                    update.close();
                }
            }catch (SQLException e){
                e.printStackTrace();
            }
            try{
                if (delete!=null ){
                    delete.close();
                }
            }catch (SQLException e){
                e.printStackTrace();
            }
     
        }
    }

    public void insert(Mark obj) {
    String sql="insert into mark ( student_id, discipline_id, mark) values (?,?,?);";
    try {
    insert=connection.prepareStatement(sql);
    insert.setInt(1, obj.getStudent_id());
    insert.setInt(2, obj.getDiscipline_id());
    insert.setInt(3, obj.getMark());
    insert.executeUpdate();
    } catch (SQLException e) {
    e.printStackTrace();
        closePreparedStatement();
    }
    }