How to achive this using servlet

Question

hi I am new to this technology... My requirement is , First I have to check whether that rebate_sku_num exists in the database or not.. If exits i need to update the row.. If now I have to insert the new row with values.. How to achive this..
my screen contains 7 rows... in will increase.. for every submit.. i have to check with the database.. whether the rebate_sku_num exists or not.. help me out.. here is my code.. i am not sure how to format my code.. in future i will do it...
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.SingleThreadModel;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import java.io.IOException;
import java.sql.ResultSet;
import java.io.*;
import java.util.*;
import java.util.Date;
import java.text.*;
public class AddRebate extends HttpServlet implements SingleThreadModel {
public void init(ServletConfig servletconfig) throws ServletException {
super.init(servletconfig);
public void doPost(HttpServletRequest httpservletrequest, HttpServletResponse httpservletresponse)
throws ServletException, IOException {
HttpSession session;
session = httpservletrequest.getSession(true);
String user_name;
String divisionCode;
String rebate_sku_num[];
String selectedMonth;
String amount[];
String message = "";
String Query="";
String RebateId="";
boolean flag = true;
// from here
Calendar todaysdate = new GregorianCalendar();
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");
SimpleDateFormat sdf1 = new SimpleDateFormat("MM/dd/yyyy HH:MM:SS");
System.out.println("today's date: " + sdf.format(todaysdate.getTime()));
String entryDate = sdf.format(todaysdate.getTime());
String entryDate1 = sdf1.format(todaysdate.getTime());
System.out.println("entering date is " +entryDate) ;
System.out.println("entering date is " +entryDate1) ;
// to here
user_name = (String) session.getAttribute("user_name");
divisionCode = (String) session.getAttribute("division_code");
selectedMonth = httpservletrequest.getParameter("selectedMonth");
rebate_sku_num = httpservletrequest.getParameterValues("rebateId");
amount = httpservletrequest.getParameterValues("amount");
System.out.println("AddRebate : doPost() : selectedMonth = " + selectedMonth);
System.out.println("AddRebate : doPost() : rebate_sku_num = " + rebate_sku_num);
System.out.println("AddRebate : doPost() : amount = " + amount);
// from here
flag = true;
for (int z = 0; z < rebate_sku_num.length && flag; z++) {
try {
flag=false;
String s = "select REBATE_SKU_NUM from EASMSA_REBATE_SKU_DETAILS_TB where REBATE_SKU_NUM ='" + rebate_sku_num[z] + "'";
System.out.println("AdjustmentServlet : doGet() : checking sku validity query = " + s);
ResultSet resultset = DatabaseConnection.executeQuery(s);
if (resultset != null) {
while (resultset.next()) {
RebateId = resultset.getString("REBATE_SKU_NUM");
flag = true;
if ((rebate_sku_num[z] != RebateId)) {
System.out.println("get the values" +rebate_sku_num);
System.out.println("get the values" + RebateId);
Query = "INSERT INTO EASMSA_REBATE_SKU_DETAILS_TB " +
"( REBATE_SKU_NUM, REBATE_DATE, REBATE_AMT, CREATED_BY," +
"CREATION_DATE, LAST_UPDATED_BY, LAST_UPDATE_DATE ) VALUES (" +
"'" + rebate_sku_num[z] + "', " +
"TO_Date( '" + "30/" + selectedMonth + "', 'dd/MM/YYYY HH:MI:SS AM'), " +
"'" + amount[z] + "' , '" + user_name + "'" +
", TO_Date( '" + entryDate + "', 'MM/dd/YYYY HH:MI:SS AM')" +
", '" + user_name + "'," +
" TO_Date( '" + entryDate + "', 'MM/dd/YYYY HH:MI:SS AM'))";
System.out.println("query is executed" +Query);
}else if ((rebate_sku_num[z] == RebateId )){
Query = "update EASMSA_REBATE_SKU_DETAILS_TB set REBATE_AMT=" + amount[z] + " where REBATE_SKU_NUM='" + rebate_sku_num[z] + "'";
System.out.println("query is executed for updation" +Query);
} else {
System.out.println("AdjustmentServlet : doGet() : checking for sku validity : resultset null");
// message = "SKU '" + sku[z] + "' of customer '" + customer[z] + "' and location '" + location[z] + "' is not valid.";
message = "SKU '" + rebate_sku_num[z] + "' is not valid.";
flag = false;
} catch (Exception exception1) {
System.out.println("AdjustmentServlet : doGet() : exception in checking validity of SKU");
exception1.printStackTrace();
// message = "SKU '" + sku[z] + "' of customer '" + customer[z] + "' and location '" + location[z] + "' is not valid.";
message = "SKU '" + rebate_sku_num[z] + "' is not valid.";
flag = false;
try {
if (DatabaseConnection.executeUpdate(Query) == 0) {
System.out.println(" AddRebate : doPost() : rollback: error in executing update query= " + Query);
DatabaseConnection.rollBack();
message = "Some problem in updating transactions. Please try again later.";
flag = false;
// break;
} else {
System.out.println("AddRebate : doPost() : update sucessfull");
message = "Rebate Transactions has been updated.";
flag = true;
} catch (Exception ex) {
System.out.println("AddRebate : doPost() : exception in update query");
message = "Some problem in updating transactions. Please try again later.";
flag = false;
ex.printStackTrace();
session.setAttribute("message", message);
httpservletresponse.sendRedirect("Welcome1.jsp?s=y");
return;

Answer 1

Oh and you can give me the dukes for helping you here:
http://forum.java.sun.com/thread.jsp?forum=45&thread=475828&tstart=0&trange=15