一. 实体类设计
图书实体类
1 public class Book { 2 3 private String id; 4 private String name; 5 private String author; 6 private double price; 7 private String description; 8 9 // 省略getter setter 10 }
购物项实体类
1 public class CartItem { 2 3 private Book book; 4 private int quantity; 5 private double price; 6 7 /** 8 * 重构getPrice方法 9 * @return 购物项总价格 10 */ 11 public double getPrice() { 12 return book.getPrice() * this.quantity; 13 } 14 public Book getBook() { 15 return book; 16 } 17 public void setBook(Book book) { 18 this.book = book; 19 } 20 public int getQuantity() { 21 return quantity; 22 } 23 public void setQuantity(int quantity) { 24 this.quantity = quantity; 25 } 26 public void setPrice(double price) { 27 this.price = price; 28 } 29 }
购物车实体类
1 public class Cart { 2 3 private Map<String, CartItem> map = new LinkedHashMap(); 4 private double price; 5 6 /** 7 * 向购物车中添加图书 8 * @param book 9 */ 10 public void add(Book book) { 11 12 CartItem item = map.get(book.getId()); 13 14 if(item == null) { 15 // 若不存在相同类型书籍，则创建新的购物项 16 item = new CartItem(); 17 item.setBook(book); 18 item.setQuantity(1); 19 // 将购物项添加到购物车中 20 map.put(book.getId(), item); 21 } else { 22 // 若存在相同类型书籍，则将购物项个数加一 23 item.setQuantity(item.getQuantity()+1); 24 } 25 } 26 /** 27 * 重构getPrice方法 28 * @return 29 */ 30 public double getPrice() { 31 32 // 购物车总价格 33 double totalprice = 0; 34 // 迭代购物车中所有购物项, 相加获取购物车总价 35 for(Map.Entry<String, CartItem> me : map.entrySet()) { 36 CartItem item = me.getValue(); 37 totalprice += item.getPrice(); 38 } 39 return totalprice; 40 } 41 public Map<String, CartItem> getMap() { 42 return map; 43 } 44 public void setMap(Map<String, CartItem> map) { 45 this.map = map; 46 } 47 public void setPrice(double price) { 48 this.price = price; 49 } 50 }
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
1 public class CartService { 2 3 BookDao bdao = new BookDao(); 4 5 /** 6 * 将图书添加到购物车中 7 * @param bookid 8 * @param cart 9 */ 10 public void buybook(String bookid, Cart cart) { 11 // 根据bookid获取图书对象 12 Book book = bdao.find(bookid); 13 cart.add(book); 14 } 15 16 /** 17 * 删除购物车中指定bookid的图书 18 * @param bookid 19 * @param cart 20 * @throws CartNotFoundException 21 */ 22 public void deleteBook(String bookid, Cart cart) throws CartNotFoundException { 23 24 //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， 25 //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。 26 if(cart == null) { 27 throw new CartNotFoundException("查找不到购物车！！！"); 28 } 29 30 //String,CartItem 31 Map map = cart.getMap(); 32 //删除key为bookid的购物项 33 map.remove(bookid); 34 } 35 36 /** 37 * 清空购物车中所有购物项 38 * @param cart 39 * @throws CartNotFoundException 40 */ 41 public void clearcart(Cart cart) throws CartNotFoundException { 42 43 if(cart == null) { 44 throw new CartNotFoundException("查找不到购物车！！！"); 45 } 46 47 cart.getMap().clear(); 48 } 49 50 /** 51 * 更新购物项数量 52 * @param cart 53 * @param bookid 54 * @param quantity 55 * @throws CartNotFoundException 56 */ 57 public void updateCart(Cart cart, String bookid, int quantity) throws CartNotFoundException { 58 59 if(cart == null) { 60 throw new CartNotFoundException("查找不到购物车！！！"); 61 } 62 63 CartItem item = cart.getMap().get(bookid); 64 item.setQuantity(quantity); 65 } 66 }
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
1 public class CartAddServlet extends HttpServlet { 2 public void doGet(HttpServletRequest request, HttpServletResponse response) 3 throws ServletException, IOException { 4 try { 5 String bookid = request.getParameter("bookid"); 6 // 从session中获取购物车 7 Cart cart = (Cart) request.getSession().getAttribute("cart"); 8 if (cart == null) { 9 //用户第一次添加商品时 10 cart = new Cart(); 11 request.getSession().setAttribute("cart", cart); 12 } 13 CartService cartService = new CartService(); 14 cartService.buybook(bookid, cart); 15 request.getRequestDispatcher("/listcart.jsp").forward(request, response); 16 return; 17 } catch (Exception e) { 18 request.setAttribute("message", "操作失败！"); 19 request.getRequestDispatcher("/message.jsp").forward(request, response); 20 return; 21 } 22 } 23 }
2. 删除购物车商品
1 public class CartDeleteServlet extends HttpServlet { 2 public void doGet(HttpServletRequest request, HttpServletResponse response) 3 throws ServletException, IOException { 4 try { 5 String bookid = request.getParameter("bookid"); 6 Cart cart = (Cart) request.getSession().getAttribute("cart"); 7 // 获取业务层, 删除目标购物项 8 CartService cartService = new CartService(); 9 cartService.deleteBook(bookid, cart); 10 // 刷新页面 11 request.getRequestDispatcher("/listcart.jsp").forward(request, response); 12 } catch (CartNotFoundException e) { 13 request.setAttribute("message", "操作出错！"); 14 request.getRequestDispatcher("/message.jsp").forward(request, response); 15 } 16 } 17 }
3. 清空购物车
1 public class ClearCartServlet extends HttpServlet { 2 public void doGet(HttpServletRequest request, HttpServletResponse response) 3 throws ServletException, IOException { 4 try { 5 Cart cart = (Cart) request.getSession().getAttribute("cart"); 6 CartService cartService = new CartService(); 7 cartService.clearcart(cart); 8 request.getRequestDispatcher("/listcart.jsp").forward(request, response); 9 } catch (CartNotFoundException e) { 10 request.setAttribute("message", "操作出错！！"); 11 request.getRequestDispatcher("/message.jsp").forward(request, response); 12 } 13 } 14 }
4. 修改购物车中购物项数量
1 public class UpdateCartServlet extends HttpServlet { 2 public void doGet(HttpServletRequest request, HttpServletResponse response) 3 throws ServletException, IOException { 4 try { 5 //获取操作的图书对象 6 String bookid = request.getParameter("bookid"); 7 //获取改变的数量 8 int quantity = Integer.parseInt(request.getParameter("quantity")); 9 //获取购物车 10 Cart cart = (Cart) request.getSession().getAttribute("cart"); 11 CartService cartService = new CartService(); 12 cartService.updateCart(cart, bookid, quantity); 13 request.getRequestDispatcher("/listcart.jsp").forward(request, response); 14 } catch (Exception e) { 15 request.setAttribute("message", "操作出错！"); 16 request.getRequestDispatcher("/message.jsp").forward(request, response); 17 } 18 } 19 }
5. 获取所有商品
1 public class ListBookServlet extends HttpServlet { 2 public void doGet(HttpServletRequest request, HttpServletResponse response) 3 throws ServletException, IOException { 4 try { 5 BookService bookService = new BookService(); 6 Map map = bookService.getAllBook(); 7 request.setAttribute("map", map); 8 request.getRequestDispatcher("/listbook.jsp").forward(request, response); 9 return; 10 } catch (Exception e) { 11 request.setAttribute("message", "请求失败！"); 12 request.getRequestDispatcher("/message.jsp").forward(request, response); 13 return; 14 } 15 } 16 }
四. 前台页面设计
listbook.jsp 获取所有商品
1 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> 2 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> 3 4 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 5 <html> 6 <head> 7 <title>My JSP 'listbook.jsp' starting page</title> 8 </head> 9 <body> 10 <table border="1px" cellspacing="0" align="center"> 11 <tr> 12 <td>图书ID</td> 13 <td>图书名称</td> 14 <td>图书作者</td> 15 <td>图书价格</td> 16 <td>图书描述</td> 17 <td>操作</td> 18 </tr> 19 <c:forEach var="me" items="${map }"> 20 <tr> 21 <td>${me.key }</td> 22 <td>${me.value.name }</td> 23 <td>${me.value.author }</td> 24 <td>${me.value.price }</td> 25 <td>${me.value.description }</td> 26 <td> 27 <a href="${pageContext.request.contextPath }/servlet/BuyServlet?bookid=${me.key }">购买</a> 28 </td> 29 </tr> 30 </c:forEach> 31 </table> 32 </body> 33 </html>
listcart.jsp 查看购物车页面
1 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> 2 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> 3 4 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 5 <html> 6 <head> 7 <title>My JSP 'listcart.jsp' starting page</title> 8 <script type="text/javascript"> 9 //删除商品 10 function clearcartitem(bookid) { 11 var result = window.confirm("您确定要删除该商品么?"); 12 if(result) { 13 window.location.href = "${pageContext.request.contextPath }/servlet/DeleteServlet?bookid="+bookid; 14 } 15 } 16 //清空购物车 17 function clearcart() { 18 var result = window.confirm("您确定要清空购物车么？"); 19 if(result) { 20 window.location.href = "${pageContext.request.contextPath }/servlet/ClearCartServlet"; 21 } 22 } 23 //改变购物项数量 24 function updateCart(input,id,oldvalue) { 25 var quantity = input.value; 26 //验证非零的正整数：^+?[1-9][0-9]*$ 27 var reg= /^+?[1-9][0-9]*$/; 28 var result = window.confirm("请确认改为：" + quantity); 29 //判断输入是否为正整数 30 if(!reg.test(quantity)) { 31 alert("参数不合法！"); 32 input.value = oldvalue; 33 return; 34 } 35 36 if(result) { 37 window.location.href="${pageContext.request.contextPath}/servlet/UpdateCartServlet?bookid="+id + "&quantity=" + quantity; 38 } else { 39 input.value = oldvalue; 40 } 41 } 42 </script> 43 </head> 44 45 <body> 46 <c:if test="${!empty(cart.map) }"> 47 <table border="1px" cellspacing="0" align="center"> 48 <tr> 49 <td>图书名称</td> 50 <td>图书作者</td> 51 <td>单价</td> 52 <td>数量</td> 53 <td>小计</td> 54 <td>操作</td> 55 </tr> 56 <c:forEach var="me" items="${cart.map }"> 57 <tr> 58 <td>${me.value.book.name }</td> 59 <td>${me.value.book.author }</td> 60 <td>${me.value.book.price }</td> 61 <td> 62 <input type="text" name="quantity" value="${me.value.quantity }" style=" 30px" onchange="updateCart(this,${me.value.book.id },${me.value.quantity })"> 63 </td> 64 <td>${me.value.price }</td> 65 <td> 66 <a href="javascript:clearcartitem(${me.value.book.id })">删除</a> 67 </td> 68 </tr> 69 </c:forEach> 70 <tr> 71 <td colspan="2"> 72 <a href="javascript:clearcart()">清空购物车</a> 73 </td> 74 <td colspan="2">合计</td> 75 <td colspan="2">${cart.price }</td> 76 </tr> 77 </table> 78 </c:if> 79 80 <c:if test="${empty(cart.map) }"> 81 对不起，您还没有购买任何商品！ 82 </c:if> 83 </body> 84 </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)
);