购物车的实现（jsp+servlet)

    购物车包括货物bean，业务逻辑处理bean（购物车bean），控制器servlet，显示页面mycart.jsp。
货物bean的属性对应了货物的数据库表的一些字段，同时加上了购买的数量。
package com.xie.shop.modal;
//货物bean
public class CartBean{
    private String id;
    private String goodName;
    private float goodsPrice;
    private int goodsNum;
    private String buyNum;
   
    public String getBuyNum() {
       return buyNum;
    }
    public void setBuyNum(String buyNum) {
       this.buyNum = buyNum;
    }
    public String getId() {
       return id;
    }
    public void setId(String id) {
       this.id = id;
    }
    public String getGoodName() {
       return goodName;
    }
    public void setGoodName(String goodName) {
       this.goodName = goodName;
    }
    public float getGoodsPrice() {
       return goodsPrice;
    }
    public void setGoodsPrice(float goodsPrice) {
       this.goodsPrice = goodsPrice;
    }
    public int getGoodsNum() {
       return goodsNum;
    }
    public void setGoodsNum(int goodsNum) {
       this.goodsNum = goodsNum;
    }
 
}
业务逻辑处理bean（购物车bean）：
主要的逻辑是：将货物编号和货物实体放入一个HashMap中，HashMap购物车bean的一个属性，同时提供了一个能返回HashMap中value所对应的货物bean
import java.sql.Connection;
import java.sql.PreparedStatement;
//购物车的业务逻辑处理
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
public class MyCartPro {
    private Connection ct=null;
    private PreparedStatement ps=null;
    private ResultSet rs=null;
    Map<String , CartBean> cMap=new HashMap<String, CartBean>();
    private float totalPrice=0;
   
      
    public float getTotalPrice() {
       return totalPrice;
    }
    public Map<String, CartBean> getcMap() {
       return cMap;
    }
    /**
     * 返回选中准备购买的货物
     * @author Administrator:centre
     * @param id：传入选中货物的编号
     * @return cb:操作成功返回一个CartBean
     */
    private CartBean getGood(String id){
    CartBean cb=new CartBean();
    try {
           ct=new ConnGood().getConn();
           ps=ct.prepareStatement("select goodsid, goodsname,goodsprice,goodsnum from goods where goodsid=?");
           ps.setString(1, id);
           rs=ps.executeQuery();
           if(rs.next()) {
              cb.setId(rs.getLong(1)+"");
              cb.setGoodName(rs.getString(2));
              cb.setGoodsPrice(rs.getFloat(3));
              cb.setGoodsNum(rs.getInt(4));
              cb.setBuyNum(1+"");
             
           }
          
       } catch (Exception e) {
           System.out.println("取得CartBean失败。");
           e.printStackTrace();
       }finally{
           closeRs();
       }     
        return cb;
   
    }
    /**
     * 将cb放入到一个map里
     * @author Administrator:centre
     * @param id:商品id
     */
    public void addBook(String id){
       if (!cMap.containsKey(id)) {
           cMap.put(id, getGood(id));        
       }else {
           cMap.get(id).setBuyNum((Integer.parseInt(cMap.get(id).getBuyNum())+1)+"");
       }
 
    }
    /**
     * 返回购物车容器
     * @author Administrator:centre
     * @return 返回购物车的容器
     */
    public Map<String , CartBean> myCart(){
       return getcMap();
    }
    /**
     * 删除选定的商品
     * @author Administrator:centre
     * @param id：货物的id
     * @return：删除成功，返回true，否则返回false
     */
    public void deleteBook(String id){
    cMap.remove(id);
    }
    /**
     * 删除购物车的所有商品
     * @author Administrator:centre
     */
    public void deleteAllBooks(){
    cMap.clear();
    }
    /**
     * 修改所有商品购买数量
     * @author Administrator:centre
     * @param id:商品id
     * @param num:商品数量
     */
    public void updateNum(String[] id,String[] num){
    for (int i = 0; i < id.length; i++) {
        if (cMap.containsKey(id[i])) {
             if (num[i].equals("0")||num[i].equals("")) {
               cMap.remove(id[i]);
            }else {
            cMap.get(id[i]).setBuyNum(num[i]);           
            }
        }         
       }
    }
    /**
     * 返回所有购买的货物
     * @author Administrator:centre
     * @return:无返回值
     */
    public List<CartBean> showMyCart(){
    List<CartBean> al=new ArrayList<CartBean>();
    Iterator<String> it=cMap.keySet().iterator();
    totalPrice=0;
    while (it.hasNext()) {
         CartBean cb=cMap.get(it.next());
         totalPrice+=Integer.parseInt(cb.getBuyNum())*cb.getGoodsPrice();
         al.add(cb);
           }
    return al;   
    }
   /**
    * @author Administrator:centre
    * 关闭相关的数据库资源
    */
   private void closeRs(){
       try {
          if (rs!=null) {
           rs.close();
           rs=null;
          }
          if (ps!=null) {
              ps.close();
              ps=null;
           }        
          if (ct!=null) {
              ct.close();
              ct=null;
           }     
    } catch (Exception e) {
       System.out.println("关闭资源失败。");
       e.printStackTrace();
    }
   }
}
控制器servlet：
如何让每个IE进程都只有唯一的一个购物车呢？我用了session。
import java.io.IOException;
import java.util.List;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.xie.shop.modal.CartBean;
import com.xie.shop.modal.MyCartPro;
 
public class MyCartServlet extends HttpServlet {
 
   
 
    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     *
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       String cartop=request.getParameter("cartop");
       if (cartop.equals("add")) {
            String id=request.getParameter("id");
            String pageNow=request.getParameter("pageNow");
            MyCartPro mcp=(MyCartPro)request.getSession().getAttribute("mycart");
            if (mcp==null) {
            //第一次购物，创建一个购物车，同时加入session
            mcp=new MyCartPro();
            request.getSession().setAttribute("mycart", mcp);
           }
            if (id!=null) {
             mcp.addBook(id);
           }      
            List<CartBean> al=mcp.showMyCart();
            request.setAttribute("alist", al);
            request.setAttribute("pageNow", pageNow);
            request.getRequestDispatcher("jsps/mycart.jsp").forward(request, response);          
       }else if (cartop.equals("delete")) {
           MyCartPro mcp=(MyCartPro)request.getSession().getAttribute("mycart");
           String id=request.getParameter("id");
           String pageNow=request.getParameter("pageNow");
           mcp.deleteBook(id);
            List<CartBean> al=mcp.showMyCart();
            request.setAttribute("alist", al);
            request.setAttribute("pageNow", pageNow);
            request.getRequestDispatcher("jsps/mycart.jsp").forward(request, response);          
       }else if (cartop.equals("deleteall")) {
           String pageNow=request.getParameter("pageNow");
           MyCartPro mcp=(MyCartPro)request.getSession().getAttribute("mycart");
           if (mcp==null) {
              request.setAttribute("pageNow", pageNow);
              request.getRequestDispatcher("index.jsp").forward(request, response);
           }else {
              mcp.deleteAllBooks();
              request.setAttribute("pageNow", pageNow);
              request.getRequestDispatcher("index.jsp").forward(request, response);           
           }
       }else if (cartop.equals("chagenum")) {
           String pageNow=request.getParameter("pageNow");
           String[] id=request.getParameterValues("goodId");
           String[] newNum=request.getParameterValues("newNum");
           /*for (int i = 0; i < id.length; i++) {
              System.out.println("id=="+id[i]+" "+"num=="+newNum[i]);
           }*/
 
           MyCartPro mcp=(MyCartPro)request.getSession().getAttribute("mycart");
            if (mcp==null) {
            request.getRequestDispatcher("jsps/mycart.jsp").forward(request, response);             
           }else {
               mcp.updateNum(id, newNum);
               List<CartBean> al=mcp.showMyCart();
               request.setAttribute("alist", al);
               request.setAttribute("pageNow", pageNow);
               request.getRequestDispatcher("jsps/mycart.jsp").forward(request, response);                
           }
          
       }
 
    }
 
    /**
     * The doPost method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to post.
     *
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {      
        this.doGet(request, response);
    }
 
}
显示页面mycart.jsp