购物车（jsp+servlet）

package pkg; import java.io.IOException; import java.io.PrintWriter; import java.util.HashMap; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class AddItemServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request,response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //设置字符的编码方式 response.setContentType("text/html;charset=GB2312"); request.setCharacterEncoding("GB2312"); //获得输出流 PrintWriter out = response.getWriter(); //获得session对象 HttpSession session=request.getSession(true); //获得用户的输入 String item=request.getParameter("item"); String amount=request.getParameter("amount"); //判断输入是否为空 if(item!=null && item.length()>0 && amount!=null && amount.length()>0){ //从sessioin对象中获得购物车 HashMap shoppingCar=(HashMap)session.getAttribute("shoppingCar"); //判断购物车是否为空 if(shoppingCar==null){ //新建购物车 shoppingCar=new HashMap(); } //取出购物车里的item的数量 String num=(String)shoppingCar.get(item); if(num==null){ //第一次购买该商品 shoppingCar.put(item, amount); }else{ int n1=Integer.parseInt(num); int n2=Integer.parseInt(amount); String result=""+(n1+n2); shoppingCar.put(item, result); } //将购物车保存到session里 session.setAttribute("shoppingCar", shoppingCar); System.out.println(shoppingCar); }else{ System.out.println("商品和数量不能为空"); } response.sendRedirect("ShoppingCart.jsp"); } }