Работа с БД. ДАО

Пишу свое первое приложение. От руководителя поступили замечания: 1.незакрытое поле! 2.выбрасывайте не SQLЕ, а ваше собственное исключение 3.я просил инкапсулировать все что касается работы с бд внутри дао. ОЧЕНЬ ПРОШУ объясните подробно что я сделал не так.

package com.oleg.dao.impl;
import com.oleg.dao.ItemDao;
import com.oleg.first.ConnectorDB;
import com.oleg.first.User;
import java.sql.*;
public class UserDatabaseDao implements ItemDao<User> {
private PreparedStatement getByIdStmt;
private PreparedStatement updateStmt;
private PreparedStatement addStmt;
private PreparedStatement deleteStmt;
Connection con = ConnectorDB.getConnection();
public UserDatabaseDao() throws Exception {
    getByIdStmt = con.prepareStatement("SELECT id, nickname, firstName, secondName, password, email FROM user WHERE id=?");
    updateStmt = con.prepareStatement("UPDATE user SET nickname=?, firstName=?, secondName=?, WHERE id=?");
    addStmt = con.prepareStatement("INSERT INTO user (nickname, firstName, secondName, password, email)" +
            " VALUES (?,?,?,?,?)");
    deleteStmt = con.prepareStatement("DELETE FROM user WHERE id=?");
}
private User getUser(ResultSet rs) throws Exception {
    try {
        User user = new User();
        user.setId(rs.getInt("id"));
        user.setNickname(rs.getString("nickname"));
        user.setFirstName(rs.getString("firstName"));
        user.setSecondName(rs.getString("secondName"));
        user.setPassword(rs.getString("password"));
        user.setEmail(rs.getString("email"));
        return user;
    } catch (Exception e) {
        System.out.println("Error return user");
    }
    throw new Exception("Error return user");
}
public User getById(int id) throws Exception {
    User user = null;
    try {
        getByIdStmt.setInt(1, id);
        ResultSet rs = getByIdStmt.executeQuery();
        if (rs.next()) {
            user = getUser(rs);
        }
        return user;
    } catch (Exception e) {
        System.out.println("Error getting user. Object is empty");
    }
    throw new Exception("Error getting user. Object is empty");
}
public void update(User user) throws Exception {
    try {
        updateStmt.setInt(4, user.getId());
    } catch (Exception e) {
        System.out.println("Error! User don't update!");
    }
}
public void add(User user) throws Exception {
    try {
        addStmt.setString(1, user.getNickname());
        addStmt.setString(2, user.getFirstName());
        addStmt.setString(3, user.getSecondName());
        addStmt.setString(4, user.getPassword());
        addStmt.setString(5, user.getEmail());
        addStmt.executeUpdate();
    } catch (Exception e) {
        System.out.println("Error! New user not added");
    }
}
public void delete(int id) throws Exception {
    try {
        deleteStmt.setInt(1, id);
        deleteStmt.executeUpdate();
    } catch (Exception e) {
        System.out.println("Error. User not deleted");
    }
}
public void closeConnection() throws Exception {
    try {
        con.close();
    } catch (Exception e) {
        System.out.println("Error. Connection is not closed");
    } finally {
        if (con != null) {
            con.close();
        }
        System.out.println("Connection close");
    }
}
public void closeStatement() throws Exception {
    try {
        getByIdStmt.close();
    } catch (Exception e) {
        System.out.println("Error! getByIdStmt is not closed");
    } finally {
        if (getByIdStmt != null) {
            getByIdStmt.close();
        }
    }
    try {
        updateStmt.close();
    } catch (Exception e) {
        System.out.println("Error! updateStmt is not closed");
    } finally {
        if (updateStmt != null) {
            updateStmt.close();
        }
    }
    try {
        addStmt.close();
    } catch (Exception e) {
        System.out.println("Error! addStmt is not closed");
    } finally {
        if (addStmt != null) {
            addStmt.close();
        }
    }
    try {
        deleteStmt.close();
    } catch (Exception e) {
        System.out.println("Error! deleteStmt is not closed");
    } finally {
        if (deleteStmt != null) {
            deleteStmt.close();
        }
    }
    System.out.println("Statement close");
}
public void exitProgram() throws Exception {
    try {
        closeStatement();
        closeConnection();
    } catch (Exception e) {
        System.out.println("Error. Program is not closed");
    } finally {
        closeStatement();
        closeConnection();
        System.out.println("Program closed!");
    }
}}
package com.oleg.first;
import com.oleg.dao.impl.*;
public class Main {
public static void main(String[] args) throws Exception {
    UserDatabaseDao userDatabaseDao = new UserDatabaseDao();
    System.out.println(userDatabaseDao.getById(1));
    userDatabaseDao.exitProgram();
}}