Connection is closed every jsp page move

I have created a db connection class.

import java.sql.*;

public class DBClass {
   private static final String driver = "com.mysql.cj.jdbc.Driver";
   private static final String url = "jdbc:mysql://localhost:3306/guestbook";
   private static final String options = "?autoReconnect=true&validationQuery=select 1&useSSL=false&serverTimezone=UTC";
   private static final String user = "root";
   private static final String pass = "*****";
   private static Connection conn = null;
   static {
       try {
           Class.forName(driver + options);
       }catch(Exception ex) {
           ex.printStackTrace();
       }
   }
   
   public static Connection getConnection() throws Exception{
       if(conn == null) {
           conn = DriverManager.getConnection(url, user, pass);
       }
       return conn;
   }
      
}

I imported it as **<%@ page import="DbClass"%>** in the writing jsp page and did Connection conn=DBClass.getConnection() . The article is well registered. But when I go to the list page, No operations allowed after connection closed. will be please tell me the cause