<Resource name="jdbc/rfid_reader"
          auth="Container" type="javax.sql.DataSource"
          maxActive="20" maxIdle="5" maxWait="10000"
          username="root" password="root."
          driverClassName="com.mysql.jdbc.Driver"
          url="jdbc:mysql://37.233.99.130:3306/rfid_reader"/>

@WebServlet("/RFIDServlet")
public class RFIDServlet extends HttpServlet {
@Resource(name = "jdbc/rfid_reader")
private DataSource dataSource;


protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    PrintWriter printWriter = response.getWriter();
    response.setContentType("text/plain");

    Connection connection = null;
    Statement statement = null;
    ResultSet resultSet = null;

    try {
        connection = dataSource.getConnection();
        String sql = "select * from cards";
        statement = connection.createStatement();
        resultSet = statement.executeQuery(sql);

        while (resultSet.next()) {
            String email = resultSet.getString("UID_card");
            printWriter.println(email);

        }

    } catch (SQLException e) {
        e.printStackTrace();
    }
   }