Can somebody pls explain me this error that I am getting when I try to run my web application on Tomcat.
java.lang.NullPointerException
business.Cart.addItem(Cart.java:27)
cart.CartServlet.doGet(CartServlet.java:49)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
The code for the Cart.java is
package business;
import java.io.Serializable;
import java.util.ArrayList;
public class Cart implements Serializable
{
private ArrayList<LineItem> items;
public Cart()
{
items = new ArrayList<LineItem>();
}
public ArrayList<LineItem> getItems()
{
return items;
}
public int getCount()
{
return items.size();
}
public void addItem(LineItem item)
{
String code = item.getProduct().getCode();
int quantity = item.getQuantity();
for(int i = 0; i<items.size(); i++)
{
LineItem lineItem = items.get(i);
if(lineItem.getProduct().getCode().equals(code))
{
lineItem.setQuantity(quantity);
return;
}
}
items.add(item);
}
public void removeItem(LineItem item)
{
String code = item.getProduct().getCode();
for(int i =0; i<items.size(); i++)
{
LineItem lineItem =items.get(i);
if(lineItem.getProduct().getCode().equals(code))
{
items.remove(i);
return;
}
}
}
}The code for the CartServlet.java is
package cart;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import business.*;
import data.*;
/**
* Servlet implementation class CartServlet
*/
public class CartServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String productCode = request.getParameter("productCode");
String quantityString = request.getParameter("quantity");
HttpSession session = request.getSession();
Cart cart = (Cart) session.getAttribute("cart");
if(cart==null)
cart = new Cart();
int quantity = 1;
try
{
quantity = Integer.parseInt(quantityString);
if(quantity < 0)
quantity = 1;
}
catch(NumberFormatException nfe)
{
quantity = 1;
}
ServletContext sc = getServletContext();
String path = sc.getRealPath("WEB-INF/products.txt");
Product product = ProductIO.getProduct(productCode, path);
LineItem lineItem = new LineItem();
lineItem.setProduct(product);
lineItem.setQuantity(quantity);
if(quantity > 0)
cart.addItem(lineItem);
else if (quantity ==0)
cart.removeItem(lineItem);
session.setAttribute("cart", cart);
String url = "/cart.jsp";
RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(url);
dispatcher.forward(request, response);
}
}