Project code

// connect to mysql
public class SqlConnector {

    private static final String CONNECTION_URL = "jdbc:mysql://localhost:3306/";

    public SqlConnector() {
    }

    public Connection getConnection(
            final String databaseName,
            final String username,
            final String password
    ) {
        try {
            return DriverManager.getConnection(CONNECTION_URL + databaseName + "?autoReconnect=true&useSSL=false", username, password);
        } catch (SQLException ex) {
            System.out.println("DATABASE_CONNECTION_ERR");
            System.out.println("Message: " + ex.getLocalizedMessage());
        }

        return null;
    }

}

// repository class for managing database
public class Repository {

    private final Connection conn;
    private PreparedStatement preparedStatement;
    private ResultSet resultSet;

    public Repository() {
        conn = new SqlConnector().getConnection("student_record", "root", "root");
        System.out.println("Connection Established!");
        createAuthTableIfNotExists();
    }

    public final void createAuthTableIfNotExists() {
        final String mAuthTable = "CREATE TABLE IF NOT EXISTS auth (uuid BINARY(16), username VARCHAR(50) PRIMARY KEY, password VARCHAR(100));";
        try {
            Statement statement = conn.createStatement();
            statement.executeUpdate(mAuthTable);
        } catch (SQLException e) {
            System.out.println("Error to create auth table. " + e.getLocalizedMessage());
        }
    }

    public boolean selectStudentRecord(String username, String password) {
        final String select = "SELECT BIN_TO_UUID(uuid) uuid FROM auth WHERE username = '"
                + username
                + "' AND password = '"
                + password
                + "';";

        try {
            preparedStatement = conn.prepareStatement(select);
            resultSet = preparedStatement.executeQuery();

            int i = 0;
            String uuid;
            while (resultSet.next()) {
                i++;
                uuid = resultSet.getString("uuid");
                System.out.println("UUID: " + uuid);
            }
            System.out.println("Result Set Count: " + i);

            preparedStatement.close();
            resultSet.close();

            if (i > 0) {
                return true;
            } else {
                return false;
            }
        } catch (SQLException ex) {
            Logger.getLogger(Repository.class.getName()).log(Level.SEVERE, null, ex);
            return false;
        }
    }

    public boolean insertStudentRecord(String username, String password) {
        final String insert = "INSERT INTO auth (uuid,username,password) VALUES (UUID_TO_BIN(UUID()),'"
                + username
                + "','"
                + password
                + "');";

        try {
            preparedStatement = conn.prepareStatement(insert);
            preparedStatement.execute();

            preparedStatement.close();
            resultSet.close();

            return true;
        } catch (SQLException ex) {
            System.out.println("Failed to create new account. Error :" + ex.getLocalizedMessage());
            return false;
        }
    }

    public boolean deleteStudentRecord(String username) {
        final String delete = "DELETE FROM  auth WHERE username = '"
                + username
                + "';";

        try {
            preparedStatement = conn.prepareStatement(delete);
            preparedStatement.execute();

            preparedStatement.close();
            resultSet.close();

            return true;
        } catch (SQLException ex) {
            System.out.println("Failed to create new account. Error :" + ex.getLocalizedMessage());
            return false;
        }
    }

}