src/model/GroupManager.java - master - Maksim_Shchelochok/Course_Work

src/model/GroupManager.java
100 строк4 KB
Maksim
Исправление орфографических ошибок
26 июн 2026, 02:27
26 июн 2026, 02:27e1279cb
package model;

import util.ConnectDatabase;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class GroupManager {
    private Connection getConnection() {
        return ConnectDatabase.getInstance().getConnection();
    }

    public List<Group> getAll() {
        List<Group> list = new ArrayList<>();
        String sql = "SELECT g.group_id, g.students_count, " +
                "g.specialty_id, s.name AS specialty_name " +
                "FROM `groups` g " +
                "JOIN specialties s ON g.specialty_id = s.specialty_id " +
                "ORDER BY g.group_id";
        try (PreparedStatement ps = getConnection().prepareStatement(sql);
             ResultSet rs = ps.executeQuery()) {
            while (rs.next()) {
                list.add(new Group(
                        rs.getInt("group_id"),
                        rs.getInt("students_count"),
                        rs.getInt("specialty_id"),
                        rs.getString("specialty_name")));
            }
        } catch (SQLException e) {
            System.out.println("Ошибка чтения групп: " + e.getMessage());
        }
        return list;
    }

    public List<Speciality> getAllSpecialities() {
        List<Speciality> list = new ArrayList<>();
        String sql = "SELECT s.specialty_id, s.name, s.direction_id, d.name AS direction_name " +
                "FROM specialties s " +
                "JOIN directions d ON s.direction_id = d.direction_id " +
                "ORDER BY s.name";
        try (PreparedStatement ps = getConnection().prepareStatement(sql);
             ResultSet rs = ps.executeQuery()) {
            while (rs.next()) {
                list.add(new Speciality(
                        rs.getInt("specialty_id"),
                        rs.getString("name"),
                        rs.getInt("direction_id"),
                        rs.getString("direction_name")));
            }
        } catch (SQLException e) {
            System.out.println("Ошибка чтения: " + e.getMessage());
        }
        return list;
    }

    public String create(int studentsCount, int specialtyId) {
        if (studentsCount < 0) {
            return "Количество студентов не может быть отрицательным.";
        }
        String sql = "INSERT INTO `groups` (students_count, specialty_id) VALUES (?, ?)";
        try (PreparedStatement ps = getConnection().prepareStatement(sql)) {
            ps.setInt(1, studentsCount);
            ps.setInt(2, specialtyId);
            ps.executeUpdate();
            return null;
        } catch (SQLException e) {
            return "Ошибка добавления: " + e.getMessage();
        }
    }

    public String update(int id, int studentsCount, int specialtyId) {
        if (studentsCount < 0) {
            return "Количество студентов не может быть отрицательным.";
        }
        String sql = "UPDATE `groups` SET students_count = ?, specialty_id = ? WHERE group_id = ?";
        try (PreparedStatement ps = getConnection().prepareStatement(sql)) {
            ps.setInt(1, studentsCount);
            ps.setInt(2, specialtyId);
            ps.setInt(3, id);
            ps.executeUpdate();
            return null;
        } catch (SQLException e) {
            return "Ошибка изменения: " + e.getMessage();
        }
    }

    public String delete(int id) {
        String sql = "DELETE FROM `groups` WHERE group_id = ?";
        try (PreparedStatement ps = getConnection().prepareStatement(sql)) {
            ps.setInt(1, id);
            ps.executeUpdate();
            return null;
        } catch (SQLException e) {
            return "Не удалось удалить: " + e.getMessage();
        }
    }
}