orderpage.java

一个网上书店的例子

package myshop;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
import java.text.*;

public class OrderPage extends HttpServlet {
  public void doGet(HttpServletRequest request,
                    HttpServletResponse response)
      throws ServletException, IOException {
    HttpSession session = request.getSession();
    ShoppingCart cart;
    synchronized(session) {
      cart = (ShoppingCart)session.getAttribute("shoppingCart");
      // New visitors get a fresh shopping cart.
      // Previous visitors keep using their existing cart.
      if (cart == null) {
        cart = new ShoppingCart();
        session.setAttribute("shoppingCart", cart);
      }
      String bookId = request.getParameter("itemId");
      String sort =request.getParameter("sort");
      if ((bookId != null)&&(sort != null)) {
        String numItemsString = request.getParameter("numItems");
        if (numItemsString == null) {
          cart.addItem(bookId,sort);
        } 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(bookId, numItems);
        }
      }
	}//end of synchronized(session)
    
    //redirect to view-session jsp
	response.sendRedirect("/myshop/cart.jsp");
  }//end of doGet()
}