session tracking remove item (urgent)

i am doing a project on a shopping mall and i had to implement the shopping cart concept.On a item description page there is a Addtocart button which goes into a servlet adds the item
in the session table and i was generating a html page on the fly giving details of that item in the a tabular form which has a Removeitem button on the last column of each row so if there are suppose 3 items purchased each item will have its own Removeitem button on its last column. if this Removeitem button is pressed a another servlet gets invoked to remove the item. My problem is that how do i known which rows Removeitem has been pressed so that i can remove that item from the session table i am
using hidden field for session tracking please help in detail if possible give a simple prg showing this
thankyou

Dear Anis:
When u r setting up the RemoveItem button in the form u need to give different value for each button like this
<input type="submit" name ="remove" value ="item1">
<input type="submit" name ="remove" value ="item2">
<input type="submit" name ="remove" value ="item3">
then in ur servlet u can get the value and check like this
String selectedItem = request.getParameter("remove");
if( selectedItem.equals("item1")){
....
else if(selectedItem.equals("item2")){
......
I hope u r getting the idea.
Anyway let me know whether this helped u r not okay
rgds
Siva

Hi!
I feel it is fairly simple. When the user want to verify his cart, use a servlet, say ServletA, to show the items selected with an option to remove the item not needed (u can use proper html input type like checkbox,radio buttion etc. as desired/required). This servlet should call another servlet, say ServletB. ServletB should parse the parameters passed to it and delete them in database using the session identification(through JDBC) after getting a final confirmation from the user. I think this u can do yourself. I am sure you will find free sites in internet for servlet where you can find source codes.
Regards,
K.Subramanian

dear mr siva
i saw your reply and it was helpful but buttons value should be Remove on every row and not item1,item2...... and so on
rgrds anis
[This message has been edited by anis mistry (edited November 27, 2000).]

Hi Anis :
Okay now i understand what u need. Infact if u want to identify the button then it SHOULD have different value like item1 item2 etc.
I saw an example in CoreSerlets book exactly like this
package coreservlets;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.text.NumberFormat;
/** Shows all items currently in ShoppingCart. Clients
* have their own session that keeps track of which
* ShoppingCart is theirs. If this is their first visit
* to the order page, a new shopping cart is created.
* Usually, people come to this page by way of a page
* showing catalog entries, so this page adds an additional
* item to the shopping cart. But users can also
* bookmark this page, access it from their history list,
* or be sent back to it by clicking on the "Update Order"
* button after changing the number of items ordered.
* <P>
* Taken from Core Servlets and JavaServer Pages
* from Prentice Hall and Sun Microsystems Press,
* http://www.coreservlets.com/.
* � 2000 Marty Hall; may be freely used or adapted.
*/
public class OrderPage extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession(true);
ShoppingCart cart;
synchronized(session) {
cart = (ShoppingCart)session.getValue("shoppingCart");
// New visitors get a fresh shopping cart.
// Previous visitors keep using their existing cart.
if (cart == null) {
cart = new ShoppingCart();
session.putValue("shoppingCart", cart);
}
String itemID = request.getParameter("itemID");
if (itemID != null) {
String numItemsString =
request.getParameter("numItems");
if (numItemsString == null) {
// If request specified an ID but no number,
// then customers came here via an "Add Item to Cart"
// button on a catalog page.
cart.addItem(itemID);
} else {
// If request specified an ID and number, then
// customers came here via an "Update Order" button
// after changing the number of items in order.
// Note that specifying a number of 0 results
// in item being deleted from cart.
int numItems;
try {
numItems = Integer.parseInt(numItemsString);
} catch(NumberFormatException nfe) {
numItems = 1;
}
cart.setNumOrdered(itemID, numItems);
}
}
}
// Whether or not the customer changed the order, show
// order status.
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Status of Your Order";
out.println(ServletUtilities.headWithTitle(title) +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1 ALIGN=\"CENTER\">" + title + "</H1>");
synchronized(session) {
Vector itemsOrdered = cart.getItemsOrdered();
if (itemsOrdered.size() == 0) {
out.println("<H2><I>No items in your cart...</I></H2>");
} else {
// If there is at least one item in cart, show table
// of items ordered.
out.println
("<TABLE BORDER=1 ALIGN=\"CENTER\">\n" +
"<TR BGCOLOR=\"#FFAD00\">\n" +
" <TH>Item ID<TH>Description\n" +
" <TH>Unit Cost<TH>Number<TH>Total Cost");
ItemOrder order;

// Rounds to two decimal places, inserts dollar
// sign (or other currency symbol), etc., as
// appropriate in current Locale.
NumberFormat formatter =
NumberFormat.getCurrencyInstance();
String formURL =
"/servlet/coreservlets.OrderPage";
// Pass URLs that reference own site through encodeURL.
formURL = response.encodeURL(formURL);

// For each entry in shopping cart, make
// table row showing ID, description, per-item
// cost, number ordered, and total cost.
// Put number ordered in textfield that user
// can change, with "Update Order" button next
// to it, which resubmits to this same page
// but specifying a different number of items.
for(int i=0; i<itemsOrdered.size(); i++) {
order = (ItemOrder)itemsOrdered.elementAt(i);
out.println
("<TR>\n" +
" <TD>" + order.getItemID() + "\n" +
" <TD>" + order.getShortDescription() + "\n" +
" <TD>" +
formatter.format(order.getUnitCost()) + "\n" +
" <TD>" +
"<FORM ACTION=\"" + formURL + "\">\n" +
"<INPUT TYPE=\"HIDDEN\" NAME=\"itemID\"\n" +
" VALUE=\"" + order.getItemID() + "\">\n" +
"<INPUT TYPE=\"TEXT\" NAME=\"numItems\"\n" +
" SIZE=3 VALUE=\"" +
order.getNumItems() + "\">\n" +
"<SMALL>\n" +
"<INPUT TYPE=\"SUBMIT\"\n "+
" VALUE=\"Update Order\">\n" +
"</SMALL>\n" +
"</FORM>\n" +
" <TD>" +
formatter.format(order.getTotalCost()));
}
String checkoutURL =
response.encodeURL("/Checkout.html");
// "Proceed to Checkout" button below table
out.println
("</TABLE>\n" +
"<FORM ACTION=\"" + checkoutURL + "\">\n" +
"<BIG><CENTER>\n" +
"<INPUT TYPE=\"SUBMIT\"\n" +
" VALUE=\"Proceed to Checkout\">\n" +
"</CENTER></BIG></FORM>");
}
out.println("</BODY></HTML>");
}
}
/** POST and GET requests handled identically. */

public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
ackage coreservlets;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
/** Base class for pages showing catalog entries.
* Servlets that extend this class must specify
* the catalog entries that they are selling and the page
* title <I>before</I> the servlet is ever accessed. This
* is done by putting calls to setItems and setTitle
* in init.
* <P>
* Taken from Core Servlets and JavaServer Pages
* from Prentice Hall and Sun Microsystems Press,
* http://www.coreservlets.com/.
* © 2000 Marty Hall; may be freely used or adapted.
*/
public abstract class CatalogPage extends HttpServlet {
private Item[] items;
private String[] itemIDs;
private String title;
/** Given an array of item IDs, look them up in the
* Catalog and put their corresponding Item entry
* into the items array. The Item contains a short
* description, a long description, and a price,
* using the item ID as the unique key.
* <P>
* Servlets that extend CatalogPage <B>must</B> call
* this method (usually from init) before the servlet
* is accessed.
*/

protected void setItems(String[] itemIDs) {
this.itemIDs = itemIDs;
items = new Item[itemIDs.length];
for(int i=0; i<items.length; i++) {
items[i] = Catalog.getItem(itemIDs[i]);
}
}
/** Sets the page title, which is displayed in
* an H1 heading in resultant page.
* <P>
* Servlets that extend CatalogPage <B>must</B> call
* this method (usually from init) before the servlet
* is accessed.
*/

protected void setTitle(String title) {
this.title = title;
}
/** First display title, then, for each catalog item,
* put its short description in a level-two (H2) heading
* with the price in parentheses and long description
* below. Below each entry, put an order button
* that submits info to the OrderPage servlet for
* the associated catalog entry.
* <P>
* To see the HTML that results from this method, do
* "View Source" on KidsBooksPage or TechBooksPage, two
* concrete classes that extend this abstract class.
*/

public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
if (items == null) {
response.sendError(response.SC_NOT_FOUND,
"Missing Items.");
return;
}
PrintWriter out = response.getWriter();
out.println(ServletUtilities.headWithTitle(title) +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1 ALIGN=\"CENTER\">" + title + "</H1>");
Item item;
for(int i=0; i<items.length; i++) {
out.println("<HR>");
item = items[i];
// Show error message if subclass lists item ID
// that's not in the catalog.
if (item == null) {
out.println("<FONT COLOR=\"RED\">" +
"Unknown item ID " + itemIDs[i] +
"</FONT>");
} else {
out.println();
String formURL =
"/servlet/coreservlets.OrderPage";
// Pass URLs that reference own site through encodeURL.
formURL = response.encodeURL(formURL);
out.println
("<FORM ACTION=\"" + formURL + "\">\n" +
"<INPUT TYPE=\"HIDDEN\" NAME=\"itemID\" " +
" VALUE=\"" + item.getItemID() + "\">\n" +
"<H2>" + item.getShortDescription() +
" ($" + item.getCost() + ")</H2>\n" +
item.getLongDescription() + "\n" +
"<P>\n<CENTER>\n" +
"<INPUT TYPE=\"SUBMIT\" " +
"VALUE=\"Add to Shopping Cart\">\n" +
"</CENTER>\n<P>\n</FORM>");
}
}
out.println("<HR>\n</BODY></HTML>");
}
/** POST and GET requests handled identically. */

public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
Hope this helps u
rgds
Siva
[This message has been edited by Sivakumar Jagadeesan (edited November 27, 2000).]

The Java Ranch has a naming policy, described here and "subramanian_k" is not a valid name. Please choose one which meets the requirements.
Thanks.

Hi!
My full name is Subramanian Kalyanasundaram, where Kalyanasundaram is my father's name. My name is K.Subramanian every where. If i replace the full name of Subramanian Kalyanasundaram it will exceed the width of UserName. So, I preferred this name. Please let me know whether I have to change my name to follow the rule.
K.Subramanian