<a href="/RegisterEvent?id=<%=Integer.parseInt(resultSet.getString("event_id")) %>">Register</a>

package com.event;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
import java.io.*;
import java.util.*;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.http.HttpSession;
import javax.servlet.http.Part;



public class RegisterEvent extends HttpServlet {



    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
int i1;


        HttpSession session = request.getSession();
        String username = (String)session.getAttribute("uname");

        String event_id = request.getParameter("id");

 String fname,lname,email,colgname,event_name;
 int contact;


        try {

            //loading drivers for mysql
            Class.forName("com.mysql.jdbc.Driver");

            //creating connection with the database
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/technovision", "root", "root");

String sql1 = "SELECT * FROM `users` WHERE `username`=?";


               PreparedStatement ps = con.prepareStatement(sql1);

               ps.setString(1,username);

       ResultSet rs = ps.executeQuery();

while(rs.next()){
        fname = rs.getString("fname");
        lname = rs.getString("lname");
        email = rs.getString("emailid");
        contact = rs.getInt("mobile");
        colgname = rs.getString("colgname");
}



  String sql2 = "SELECT event_name FROM events WHERE event_id=?";


               PreparedStatement ps1 = con.prepareStatement(sql2);

               ps1.setInt(1,Integer.parseInt(event_id));



       ResultSet rs1 = ps1.executeQuery();


       while(rs1.next())
       {  event_name = rs1.getString("event_name");
       }




  String sql3 ="INSERT INTO registered_users(`fname`,`lname`,`email`,`contact`,`college_name`,`event_name`) values (?,?,?,?,?,?)";


          PreparedStatement ps3 = con.prepareStatement(sql3);


               ps3.setString(1, fname);
               ps3.setString(2, lname);
               ps3.setString(3, email);
               ps3.setInt(4, contact);
               ps3.setString(5, colgname);
               ps3.setString(6, event_name);

           i1 = ps3.executeUpdate();

       if(i1>0)
                 {
                response.sendRedirect("register-success.jsp");
                 }

        }
        catch (Exception se) {
            System.out.println(se);
        }


    }
}