MySQLHelper Java 类：用于 OnlineTrainingHub 项目的数据库操作

/**

• MySQL数据库操作类 */ public class MySQLHelper { private Connection conn; private PreparedStatement ps; private ResultSet rs;

  public MySQLHelper() { try { Class.forName('com.mysql.jdbc.Driver'); conn = DriverManager.getConnection('jdbc:mysql://localhost:3306/OnlineTrainingHub', 'root', 'password'); } catch (ClassNotFoundException | SQLException e) { e.printStackTrace(); } }

  public void addUser(User user) { String sql = 'INSERT INTO User (userName, userID, password) VALUES (?, ?, ?)'; try { ps = conn.prepareStatement(sql); ps.setString(1, user.getUserName()); ps.setString(2, user.getUserID()); ps.setString(3, user.getPassword()); ps.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } }

  public User getUser(String userID, String password) { String sql = 'SELECT * FROM User WHERE userID=? AND password=?'; try { ps = conn.prepareStatement(sql); ps.setString(1, userID); ps.setString(2, password); rs = ps.executeQuery(); if (rs.next()) { String userName = rs.getString('userName'); return new User(userName, userID, password); } } catch (SQLException e) { e.printStackTrace(); } return null; }

  public void addQuestion(Question question) { String sql = 'INSERT INTO Question (questionID, questionText, optionA, optionB, optionC, optionD, answer) VALUES (?, ?, ?, ?, ?, ?, ?)'; try { ps = conn.prepareStatement(sql); ps.setInt(1, question.getQuestionID()); ps.setString(2, question.getQuestionText()); ps.setString(3, question.getOptionA()); ps.setString(4, question.getOptionB()); ps.setString(5, question.getOptionC()); ps.setString(6, question.getOptionD()); ps.setString(7, question.getAnswer()); ps.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } }

  public List getQuestionList() { String sql = 'SELECT * FROM Question'; List questionList = new ArrayList<>(); try { ps = conn.prepareStatement(sql); rs = ps.executeQuery(); while (rs.next()) { int questionID = rs.getInt('questionID'); String questionText = rs.getString('questionText'); String optionA = rs.getString('optionA'); String optionB = rs.getString('optionB'); String optionC = rs.getString('optionC'); String optionD = rs.getString('optionD'); String answer = rs.getString('answer'); Question question = new Question(questionID, questionText, optionA, optionB, optionC, optionD, answer); questionList.add(question); } } catch (SQLException e) { e.printStackTrace(); } return questionList; } }