购物车实现

AddCartServlet.java

package com.exp.web.servlet;

import com.exp.bookstore.model.Product;
import com.exp.bookstore.service.ProductService;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

@WebServlet("/addCart")
public class AddCartServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取id
        String id = request.getParameter("id");

        //2.通过id查询数据库对应商品
        ProductService ps = new ProductService();
        Product p = ps.findBook(id);

        //3.把购买商品放在购物车Map
        //3.1先从session获取购物车数据[cart]
        Map<Product,Integer> cart = (Map<Product, Integer>) request.getSession().getAttribute("cart");
        //3.2如果没有购物车数据，就创建一个map对象
        if(cart == null){
            cart = new HashMap<Product,Integer>();
            cart.put(p,1);//首次加入购物车
        }else{
            //3.3 判断map里面是否有当前想购物商品
            if(cart.containsKey(p)){
                cart.put(p,cart.get(p)+1);
            }else{
                cart.put(p,1);
            }
        }

        //4.打印购物车数据
        for(Map.Entry<Product,Integer> entry: cart.entrySet()){
            System.out.println(entry.getKey() + "数量" + entry.getValue());
        }

        //5.存session
        request.getSession().setAttribute("cart",cart);

        //6.响应客户端面
        //继续购物，查看购物车
        //6.响应客户端面
        //继续购物，查看购物车
        String a1 = "<a href=\"" + request.getContextPath()+"/showProductByPage\">继续购物</a>";
        String a2 = "&nbsp;&nbsp;<a href=\"" + request.getContextPath()+"/cart.jsp\">查看购物车</a>";
        response.getWriter().write(a1);//write可以多次写入
        response.getWriter().write(a2);
    }
    public static void main(String[] args) {
        //map
        Map<Product, Integer> cart = new HashMap<Product, Integer>();

        ProductService ps = new ProductService();
        Product p1 = ps.findBook("2");
        cart.put(p1, 1);

        Product p2 = ps.findBook("2");
        /**
         * 默认情况下，key是根据地址来判断是否存在
         * 所以要改比较规则,重写equals方法
        */
        if(cart.containsKey(p2)){
            System.out.println("p2已经在购物车存在");
        }else{
            System.out.println("p2在购物车不存在");
        }
    }
}

cart.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>电子书城</title>
<link rel="stylesheet" href="css/main.css" type="text/css" />


</head>

<body class="main">

    <jsp:include page="head.jsp" />

    <jsp:include page="menu_search.jsp" />


    <div id="divpagecontent">
        <table width="100%" border="0" cellspacing="0">
            <tr>

                <td><div style="text-align:right; margin:5px 10px 5px 0px">
                        <a href="index.html">首页</a>&nbsp;&nbsp;&nbsp;&nbsp;&gt;&nbsp;&nbsp;&nbsp;&nbsp;购物车
                    </div>

                    <table cellspacing="0" class="infocontent">
                        <tr>
                            <td><img src="ad/page_ad.jpg" width="666" height="89" />
                                <table width="100%" border="0" cellspacing="0">
                                    <tr>
                                        <td><img src="images/buy1.gif" width="635" height="38" />
                                        </td>
                                    </tr>
                                    <tr>
                                        <td>
                                            <table cellspacing="1" class="carttable">
                                                <tr>
                                                    <td width="10%">序号</td>
                                                    <td width="30%">商品名称</td>
                                                    <td width="10%">价格</td>
                                                    <td width="20%">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;数量</td>
                                                    <td width="10%">库存</td>
                                                    <td width="10%">小计</td>
                                                    <td width="10%">取消</td>
                                                </tr>
                                            </table> 
                                                <table width="100%" border="0" cellspacing="0">
                                                    <%--定义一个总价格的变量--%>
                                                    <c:set var="totalPrice" value="0"></c:set>
                                                    <c:forEach items="${cart}" var="entry">
                                                        <tr>
                                                            <td width="10%">1</td>
                                                            <td width="30%">${entry.key.name}</td>

                                                            <td width="10%">${entry.key.price}</td>
                                                            <td width="20%">
                                                                <input type="button" value='-'
                                                                       style="width:20px">

                                                                <input name="text" type="text"  value="${entry.value}"
                                                                       style="width:40px;text-align:center" /> <input
                                                                    type="button" value='+' style="width:20px">

                                                            </td>
                                                            <td width="10%">${entry.key.pnum}</td>
                                                            <td width="10%">${entry.value*entry.key.price}</td>

                                                            <td width="10%"><a href="#"
                                                                               style="color:#FF0000; font-weight:bold">X</a></td>
                                                        </tr>
                                                        <!-- 累计总价格 -->
                                                        <c:set var="totalPrice" value="${totalPrice+ entry.value*entry.key.price}"></c:set>
                                                    </c:forEach>
                                                </table>
                                                


                                            <table cellspacing="1" class="carttable">
                                                <tr>
                                                    <td style="text-align:right; padding-right:40px;"><font
                                                        style="color:#FF6600; font-weight:bold">合计：  ${totalPrice}元</font>
                                                    </td>
                                                </tr>
                                            </table>
                                            <div style="text-align:right; margin-top:10px">
                                                <a
                                                    href="product_list.jsp"><img
                                                    src="images/gwc_jx.gif" border="0" /> </a>

                                                &nbsp;&nbsp;&nbsp;&nbsp;<a
                                                    href="order.jsp"><img
                                                    src="images/gwc_buy.gif" border="0" /> </a>
                                            </div>
                                        </td>
                                    </tr>
                                </table>
                            </td>
                        </tr>
                    </table></td>
            </tr>
        </table>
    </div>



    <jsp:include page="foot.jsp" />


</body>
</html>