一. 实体类设计

图书实体类

 public class Book {

     private String id;

     private String name;

     private String author;

     private double price;

     private String description;

     // 省略getter setter

 }

购物项实体类

 public class CartItem {

     private Book book;

     private int quantity;

     private double price;

     /**

      * 重构getPrice方法

      * @return 购物项总价格

      */

     public double getPrice() {

         return book.getPrice() * this.quantity;

     }

     public Book getBook() {

         return book;

     }

     public void setBook(Book book) {

         this.book = book;

     }

     public int getQuantity() {

         return quantity;

     }

     public void setQuantity(int quantity) {

         this.quantity = quantity;

     }

     public void setPrice(double price) {

         this.price = price;

     }

 }

购物车实体类

 public class Cart {

     private Map<String, CartItem> map = new LinkedHashMap();

     private double price;

     /**

      * 向购物车中添加图书

      * @param book

      */

     public void add(Book book) {

         CartItem item = map.get(book.getId());

         if(item == null) {

             // 若不存在相同类型书籍，则创建新的购物项

             item = new CartItem();

             item.setBook(book);

             item.setQuantity(1);

             // 将购物项添加到购物车中

             map.put(book.getId(), item);

         } else {

             // 若存在相同类型书籍，则将购物项个数加一

             item.setQuantity(item.getQuantity()+1);

         }

     }

     /**

      * 重构getPrice方法

      * @return

      */

     public double getPrice() {

         // 购物车总价格

         double totalprice = 0;

         // 迭代购物车中所有购物项, 相加获取购物车总价

         for(Map.Entry<String, CartItem> me : map.entrySet()) {

             CartItem item = me.getValue();

             totalprice += item.getPrice();

         }

         return totalprice;

     }

     public Map<String, CartItem> getMap() {

         return map;

     }

     public void setMap(Map<String, CartItem> map) {

         this.map = map;

     }

     public void setPrice(double price) {

         this.price = price;

     }

 }

二. 业务层设计

操作购物车实际上就是操作cart对象中的map集合

购物车四个主要功能:

1. 添加商品到购物车

2. 删除购物车商品

3. 清空购物车

4. 修改购物车中购物项数量

 public class CartService {

     BookDao bdao = new BookDao();

     /**

      * 将图书添加到购物车中

      * @param bookid

      * @param cart

      */

     public void buybook(String bookid, Cart cart) {

         // 根据bookid获取图书对象

         Book book = bdao.find(bookid);

         cart.add(book);

     }

     /**

      * 删除购物车中指定bookid的图书

      * @param bookid

      * @param cart

      * @throws CartNotFoundException

      */

     public void deleteBook(String bookid, Cart cart) throws CartNotFoundException {

         //如果用户直接访问DeleteServlet，那么当运行到这里时，因为cart对象为空，

         //程序会抛出空指针异常。所以这里应该判断购物车是否为空。

         if(cart == null) {

             throw new CartNotFoundException("查找不到购物车！！！");

         }

         //String,CartItem

         Map map = cart.getMap();

         //删除key为bookid的购物项

         map.remove(bookid);

     }

     /**

      * 清空购物车中所有购物项

      * @param cart

      * @throws CartNotFoundException

      */

     public void clearcart(Cart cart) throws CartNotFoundException {

         if(cart == null) {

             throw new CartNotFoundException("查找不到购物车！！！");

         }

         cart.getMap().clear();

     }

     /**

      * 更新购物项数量

      * @param cart

      * @param bookid

      * @param quantity

      * @throws CartNotFoundException

      */

     public void updateCart(Cart cart, String bookid, int quantity) throws CartNotFoundException {

         if(cart == null) {

             throw new CartNotFoundException("查找不到购物车！！！");

         }

         CartItem item = cart.getMap().get(bookid);

         item.setQuantity(quantity);

     }

 }

注意: 获取到web层传递过来的cart对象时, 记得检查NPE

三. web层设计

1. 添加商品到购物车

 public class CartAddServlet extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         try {

             String bookid = request.getParameter("bookid");

             // 从session中获取购物车

             Cart cart = (Cart) request.getSession().getAttribute("cart");

             if (cart == null) {

                 //用户第一次添加商品时

                 cart = new Cart();

                 request.getSession().setAttribute("cart", cart);

             }

             CartService cartService = new CartService();

             cartService.buybook(bookid, cart);

             request.getRequestDispatcher("/listcart.jsp").forward(request, response);

             return;

         } catch (Exception e) {

             request.setAttribute("message", "操作失败！");

             request.getRequestDispatcher("/message.jsp").forward(request, response);

             return;

         }

     }

 }

2. 删除购物车商品

 public class CartDeleteServlet extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         try {

             String bookid = request.getParameter("bookid");

             Cart cart = (Cart) request.getSession().getAttribute("cart");

             // 获取业务层, 删除目标购物项

             CartService cartService = new CartService();

             cartService.deleteBook(bookid, cart);

             // 刷新页面

             request.getRequestDispatcher("/listcart.jsp").forward(request, response);

         } catch (CartNotFoundException e) {

             request.setAttribute("message", "操作出错！");

             request.getRequestDispatcher("/message.jsp").forward(request, response);

         }

     }

 }

3. 清空购物车

 public class ClearCartServlet extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         try {

             Cart cart = (Cart) request.getSession().getAttribute("cart");

             CartService cartService = new CartService();

             cartService.clearcart(cart);

             request.getRequestDispatcher("/listcart.jsp").forward(request, response);

         } catch (CartNotFoundException e) {

             request.setAttribute("message", "操作出错！！");

             request.getRequestDispatcher("/message.jsp").forward(request, response);

         }

     }

 }

4. 修改购物车中购物项数量

 public class UpdateCartServlet extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         try {

             //获取操作的图书对象

             String bookid = request.getParameter("bookid");

             //获取改变的数量

             int quantity = Integer.parseInt(request.getParameter("quantity"));

             //获取购物车

             Cart cart = (Cart) request.getSession().getAttribute("cart");

             CartService cartService = new CartService();

             cartService.updateCart(cart, bookid, quantity);

             request.getRequestDispatcher("/listcart.jsp").forward(request, response);

         } catch (Exception e) {

             request.setAttribute("message", "操作出错！");

             request.getRequestDispatcher("/message.jsp").forward(request, response);

         }

     }

 }

5. 获取所有商品

 public class ListBookServlet extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         try {

             BookService bookService = new BookService();

             Map map = bookService.getAllBook();

             request.setAttribute("map", map);

             request.getRequestDispatcher("/listbook.jsp").forward(request, response);

             return;

         } catch (Exception e) {

             request.setAttribute("message", "请求失败！");

             request.getRequestDispatcher("/message.jsp").forward(request, response);

             return;

         }

     }

 }

四. 前台页面设计

listbook.jsp 获取所有商品

 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

 <html>

   <head>

     <title>My JSP 'listbook.jsp' starting page</title>

   </head>

   <body>

     <table border="1px" cellspacing="0" align="center">

         <tr>

             <td>图书ID</td>

             <td>图书名称</td>

             <td>图书作者</td>

             <td>图书价格</td>

             <td>图书描述</td>

             <td>操作</td>

         </tr>

            <c:forEach var="me" items="${map }">

             <tr>

                 <td>${me.key }</td>

                 <td>${me.value.name }</td>

                 <td>${me.value.author }</td>

                 <td>${me.value.price }</td>

                 <td>${me.value.description }</td>

                 <td>

                     <a href="${pageContext.request.contextPath }/servlet/BuyServlet?bookid=${me.key }">购买</a>

                 </td>

                </tr>

            </c:forEach>

     </table>

   </body>

 </html>

listcart.jsp 查看购物车页面

 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

 <html>

   <head>

     <title>My JSP 'listcart.jsp' starting page</title>

     <script type="text/javascript">

         //删除商品

         function clearcartitem(bookid) {

             var result = window.confirm("您确定要删除该商品么?");

             if(result) {

                 window.location.href = "${pageContext.request.contextPath }/servlet/DeleteServlet?bookid="+bookid;

             }

         }

         //清空购物车

         function clearcart() {

             var result = window.confirm("您确定要清空购物车么？");

             if(result) {

                 window.location.href = "${pageContext.request.contextPath }/servlet/ClearCartServlet";

             }

         }

         //改变购物项数量

         function updateCart(input,id,oldvalue) {

             var quantity = input.value;

             //验证非零的正整数：^\+?[1-9][0-9]*$

             var reg= /^\+?[1-9][0-9]*$/;

             var result = window.confirm("请确认改为：" + quantity);

             //判断输入是否为正整数

             if(!reg.test(quantity)) {

                 alert("参数不合法！");

                 input.value = oldvalue;

                 return;

             }

             if(result) {

                 window.location.href="${pageContext.request.contextPath}/servlet/UpdateCartServlet?bookid="+id + "&quantity=" + quantity;

             } else {

                 input.value = oldvalue;

             }

         }

     </script>

   </head>

   <body>

       <c:if test="${!empty(cart.map) }">

     <table border="1px" cellspacing="0" align="center">

         <tr>

             <td>图书名称</td>

             <td>图书作者</td>

             <td>单价</td>

             <td>数量</td>

             <td>小计</td>

             <td>操作</td>

         </tr>

            <c:forEach var="me" items="${cart.map }">

             <tr>

                 <td>${me.value.book.name }</td>

                 <td>${me.value.book.author }</td>

                 <td>${me.value.book.price }</td>

                 <td>

                     <input type="text" name="quantity" value="${me.value.quantity }" style="width: 30px" onchange="updateCart(this,${me.value.book.id },${me.value.quantity })">

                 </td>

                 <td>${me.value.price }</td>

                 <td>

                     <a href="javascript:clearcartitem(${me.value.book.id })">删除</a>

                 </td>

                </tr>

            </c:forEach>

            <tr>

             <td colspan="2">

                 <a href="javascript:clearcart()">清空购物车</a>

             </td>

             <td colspan="2">合计</td>

             <td colspan="2">${cart.price }</td>

         </tr>

     </table>

     </c:if>

     <c:if test="${empty(cart.map) }">

         对不起，您还没有购买任何商品！

     </c:if>

   </body>

 </html>

附: 数据库表

create database cart_cheatsheep;

use cart_cheatsheep;

create table t_book(

    id varchar(40) primary key,

    name varchar(100) not null unique,

    author varchar(100) not null unique,

    price double not null,

    description varchar(255)

);

巴特西

JavaWeb开发购物车设计总结

一. 实体类设计

二. 业务层设计

三. web层设计

四. 前台页面设计

附: 数据库表

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