Online Shopping

Hi, I have written an Online Shopping system. But, there a bug in it. Whenever I add an item, it is getting added twice. It will be great if anybody can point where the error is.Thanks in advance.

Source code is as follows:

index.jsp

show.jsp

<%@ page session = "true" %>
<%@ include file = "header.jsp" %>
<br>
<%@ include file = "menu.jsp" %>
<br>
<br>
<br>
<br>
<%@ page import = "java.sql.*" %> 
<%@ page import = "sample.Cart" %> 
<%@page import = "java.util.ArrayList" %>

<%String category_id = request.getParameter("category_id");
 
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
 
Connection con = DriverManager.getConnection("jdbc:odbc:myDataSource");
Statement st = con.createStatement();

System.out.println("Category I s is"+category_id);
 
String sql = "select * from Products where Category_id = '"+category_id+"'";
System.out.println(sql);
ResultSet rs = st.executeQuery(sql);
//cart = session.getAttribute("cart");
 Cart cart = new Cart();
ArrayList al = (ArrayList)session.getAttribute("al");

String productId = "";
String productDescription = "";
String name = "";
String price = "";
String categoryId = "";

while(rs.next())
{
 productId = rs.getString(1);
 productDescription = rs.getString(2);
 name = rs.getString(3);
 price = rs.getString(4);
 categoryId = rs.getString(5);
 
//session.setAttribute("categoryId",category_id);
// session.setAttribute("productId",productId);
 
session.setAttribute("al",al);
 
out.println("<form method = \"POST\" action =\"Cart1.jsp\"> ");
out.println("<table width = \"80%\" height = \"97\" border= \"1\" align = \"right\">");

out.println("<tr><td>"+productId+"</td></tr>");
out.println("<tr><td>"+productDescription+"</td></tr>");
out.println("<tr><td>"+name+"</td></tr>");
out.println("<tr><td>"+price+"</td></tr>");
out.println("<tr><td>"+categoryId+"</td></tr>");
 
out.println("<tr><td><input type = \"text\" size = \"2\" name =\"NOI\"</td></tr>");
 
out.println("<tr><td><input type = \"submit\" name = \"submit\" value = \"Add to cart\"></td></tr>");
 
out.println("</table>");
out.println("</form>");
}
 
cart.setCategoryId(categoryId);
cart.setProductId(productId);
session.setAttribute("cart", cart);
if(cart != null){
if(al != null){
al = (ArrayList)session.getAttribute("al");
al.add(cart);
}
else{
al = new ArrayList();
//session.setAttribute("al",al);
al.add(cart);
}
}//cart if
 
 
}
catch(ClassNotFoundException ce)
{
System.out.println("ClassNotFoundException");
}
catch(SQLException se)
{
System.out.println("SQL Exception"+se.getMessage());
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
 
 
 
%>

Cart1.jsp

Cart.java

You are adding it in show.jsp and cart1.jsp

show.jsp

cart1.jsp

why do you want to add it in show.jsp? From the name I infer it should only display the items in cart. Not try to add an item.