Upload Excel to Java Servlet and get result while the data is being uploaded

I have an application where i try to upload a excel file (approx 21,000 rows) from a browser - The application is written in JSP , Servlet , Apache POI and JDBC. Now when the file is uploaded from browser(jsp file) using Servlet and then read the records of excel file using Apache POI and then write the rows to the MySQL database. The upload runs successfully and able to insert records in to Mysql database. However, the jsp page just stays there and user is notified of the successful upload only after few minutes.

Can anyone help me How do i show the user a message on the browser that file has been uploaded successfully but it is getting processed ? Any better implementation of the code also please let me know. My Servlet code is as below

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;
import java.util.logging.Logger;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FilenameUtils;
import org.json.simple.JSONObject;

import src.com.pion.web.config.business.UploadFileProcessor;

/**
 * Servlet implementation class UploadServlet
 */
@WebServlet(name = "UploadServlet",
description = "Manages the uploaded servlet file and sends it to processing", 
urlPatterns = { "/upload.do" }
)
public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private static final Logger LOGGER = Logger.getLogger(UploadServlet.class.getName());

     private static final String UPLOAD_DIRECTORY = "upload";
        private static final int THRESHOLD_SIZE     = 1024 * 1024 * 3;  // 3MB
        private static final int MAX_FILE_SIZE      = 1024 * 1024 * 40; // 40MB
        private static final int MAX_REQUEST_SIZE   = 1024 * 1024 * 50; // 50MB

    public UploadServlet() {
        super();
    }




    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        throw new ServletException("GET method used with " +
                getClass( ).getName( )+": POST method required.");
    }

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

        //PrintWriter to send the JSON response back
        // checks if the request actually contains upload file
        if (!ServletFileUpload.isMultipartContent(request)) {
            PrintWriter writer = response.getWriter();
            writer.println("Request does not contain upload data");
            writer.flush();
            return;
        }
        PrintWriter out = response.getWriter();

        //set content type and header attributes
        response.setContentType("text/html");
        response.setHeader("Cache-control", "no-cache, no-store");
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Expires", "-1");

     // configures upload settings
        DiskFileItemFactory factory = new DiskFileItemFactory();
        factory.setSizeThreshold(THRESHOLD_SIZE);
        factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

        ServletFileUpload upload = new ServletFileUpload(factory);
        upload.setFileSizeMax(MAX_FILE_SIZE);
        upload.setSizeMax(MAX_REQUEST_SIZE);

        // constructs the directory path to store upload file
        String uploadPath = getServletContext().getRealPath("")
            + File.separator + UPLOAD_DIRECTORY;
        // creates the directory if it does not exist
        File uploadDir = new File(uploadPath);
        if (!uploadDir.exists()) {
            uploadDir.mkdir();
        }

        JSONObject myObj = new JSONObject();

        String fileName = null;
        String fullName = null;
        File file = null;

        try {

            // parses the request's content to extract file data
            List formItems = upload.parseRequest(request);
            Iterator iter = formItems.iterator();

            // iterates over form's fields
            while (iter.hasNext()) {
                FileItem item = (FileItem) iter.next();
                // processes only fields that are not form fields
                if (!item.isFormField()) {
                    fileName = new File(item.getName()).getName();
                    String filePath = uploadPath + File.separator + fileName;
                    file = new File(filePath);
                    fullName = item.getName().trim(); 
                    // saves the file on disk
                    item.write(file);
                }
            }           String message = null;
            UploadFileProcessor uploadProcessor = new UploadFileProcessor();
            String extension = FilenameUtils.getExtension(fullName);
            if(extenter code hereension.trim().equalsIgnoreCase("xlsx")){
                 // Send the code for processing and later insert into database
                message = uploadProces`enter code `enter code here`here`sor.processExcelFile(file);
            }

            myObj.put("success", true);
            myObj.put("message", message + " item(s) were processed for file " + fileName);
            LOGGER.info(myObj.toString());
        }
        catch(FileUploadException ex) {
            log("Error encountered while parsing the request",ex);
            myObj.put("success", false);
            LOGGER.info(myObj.toString());
        } catch(Exception ex) {
            log("Error encountered while uploading file",ex);
            myObj.put("success", false);
            LOGGER.info(myObj.toString());
        }
        out.close();
    }
}