JavaWeb开发购物车设计总结

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)
);