基于Javabean与JSP的购物车功能

浅谈实现基于Javabean与JSP的购物车功能

　　首先呢，在买了东西之后要放在购物车里，当车子里的物品有相同时就叠加，不再创建物品对象，有了物品之后肯 定要有价格，数量等等对象。这些对象我们要封装在JAVABEAN 中的!有了Javabean就需要建立SERVLET来进行与业务层连接，我们就需要有，增加购物车，删除购物车，清楚购物车等一系列的Servlet和SERVICE层连接!SERVICE层调用DAO层，这些步骤正体现出了MVC的设计模式!下面我们看具体的实现基于Javabean与JSP的购物车功能吧!

　　(1) 1. 代表购物车的ShoppingCart 类

public class ShoppingCart {  
 //装载 ShoppingCartItem 的数据结构: Map, 键： 书的 id, 值: 书对应的 ShoppingCartItem  
 private Map<String, ShoppingCartItem> books = null;  
   
 public ShoppingCart(){  
  books = new HashMap<String, ShoppingCartItem>();  
 }   
 
 public Map<String, ShoppingCartItem> getBooks() {  
  return books;  
 }  
   
 public Book getBook(String bookId){  
  Book book = null;  
    
  ShoppingCartItem sci = this.books.get(bookId);  
  if (sci == null)  
   return null;  
    
  return sci.getBook ();  
 }  
   
 public float getTotalPrice(){  
  float totalPrice = 0.0f;  
    
  //对 books 中的 value 进行遍历, 取其 price 属性的和   
  Iterator<ShoppingCartItem> iterator = books.values().iterator ();  
  while(iterator.hasNext()){  
   ShoppingCartItem sci = iterator.next();  
   totalPrice += sci.getPrice();  
  }   
    
  return totalPrice;  
 }  
   
 public int getTotalQuantity(){  
  int quantity = 0;  
    
  //对 books 中的 value 进行遍历, 取其 quantity 属性的和  
  Iterator<ShoppingCartItem> iterator = books.values().iterator();  
  while(iterator.hasNext()) {  
   ShoppingCartItem sci = iterator.next();  
   quantity += sci.getQuantity();  
  }  
    
  return quantity;  
 }   
   
 public boolean isExistInShoppingCart(String bookId){  
  return this.books.get(bookId) != null;  
 }  
   
 public ShoppingCartItem getShoppingCartItemByBookId(String bookId){  
  return this.books.get(bookId);  
 }   
   
 public void addNewItemToShoppingCart(ShoppingCartItem sci) {  
  this.books.put(sci.getBook().getId(), sci);  
 }  
} 

2. 代表购物车中的物品

public class ShoppingCartItem {  
 //具体指向某本书  
 private Book book;  
   
 //当前商品在购物车中的数量  
 private int quantity;  
   
 public ShoppingCartItem(Book book) {  
  this.book = book;  
  this.quantity = 1;  
 }  
 
 //当前商品的总价格  
 private float price;  
   
 public void incrementQuantity(){  
  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 float getPrice() {  
  return this.book.getPrice() * this.quantity;  
 }  
 
} 

(2)建立DAO,此时有人会问，这次DAO为什么没有购物车呢，因为购物车是没有数据的，而是里面的物品才有 数据的，当有更新购物车里面的物品时才会早DAO里面写方法！

public class BookDAO {  
   
 //  
 public void upadateBookQuantityByBookId(Connection conn, String bookId, int quantity){  
  String sql = "UPDATE books SET saleAmount = saleAmount + ? WHERE id = ?";  
  Object [] params = new Object[]{quantity, bookId};  
    
  QueryRunner queryRunner = new QueryRunner ();  
    
  try {  
   queryRunner.update(conn, sql, params);  
  } catch (SQLException e) {  
   // TODO Auto-generated catch block  
   e.printStackTrace();  
   throw new RuntimeException (MyBookStoreConstants.UPDATE_BOOK_SALEAMOUNT_BY_BOOK_ID_EXCEPTION);  
  }  
 } 

(3) 建立业务层,涉及到添加，清空等方法！这边佟刚老师的代码都有详细的解释！

public class BookService {  
 //根据给定的 ShoppingCart 对象, 调用 DAO 方法进行数据库更新操作  
 public void buyBooks(ShoppingCart sc){  
  //对 sc 中的 ShoppingCartItem 对象进行遍历, 调用 BookDAO.upadateBookQuantityByBookId 方法  
  Connection conn = null;  
  conn = DBHelper.getConnection();  
    
  try {  
   Iterator<ShoppingCartItem> shoppingCartItemSet = sc.getBooks().values ().iterator();  
   BookDAO bookDAO = new BookDAO ();  
     
   while(shoppingCartItemSet.hasNext()) {  
    ShoppingCartItem sci = shoppingCartItemSet.next ();  
      
    String bookId = sci.getBook().getId ();  
    int quantity = sci.getQuantity ();  
      
    bookDAO.upadateBookQuantityByBookId(conn, bookId, quantity);  
   }  
  }finally {  
   DBHelper.releaseDBSource(null, null, conn);  
  }   
    
    
 }  
   
 //参数 items 中的键为 书的 id 号, 值为购 物车中对应的 数量  
 public void updateShoppingCart(Map<String,Integer> items, ShoppingCart sc){  
  Set<String> keySet = null;  
  keySet = items.keySet ();  
    
  for(Iterator<String> it = keySet.iterator(); it.hasNext(); ) {  
   String bookId = it.next();  
   int quantity = items.get (bookId);  
     
   if(quantity <= 0) {  
    sc.getBooks().remove(bookId);  
   }else {  
    sc.getShoppingCartItemByBookId(bookId).setQuantity (quantity);  
   }  
      
  }  
 }   
   
 //清空购物车  
 public void clearShoppingCart(ShoppingCart sc) {  
  sc.getBooks().clear();  
 }  
   
 public void deleteShoppingCartItemById(String id, ShoppingCart sc){  
  //删除 sc 中的 id 元素   
  sc.getBooks().remove(id);  
 }  
   
 //把 id 对应的 ShoppingCartItem 对象放入购物车 ShoppingCart 对象中  
 public void addToShoppingCart(String id, ShoppingCart sc) {  
    
  //1. 查看 sc 中有没有 id 对应的 ShoppingCartItem 对象   
  if(sc.isExistInShoppingCart(id)){  
   //1.1 有: 把该对象取出, 使其数量 + 1, 调用 sci.increseQuantity(); 方法  
   ShoppingCartItem scsci = sc.getShoppingCartItemByBookId(id);  
   sci.incrementQuantity();  
  }   
  //1.2 没有: 创建一个新的 ShoppingCartItem 对象, 并将其放入 sc 中, 以书的 id 作为键   
  else{  
   //1.2.1 根据 id 获取相应的 Book 对象, 调用 BookDAO 的 selectBookByBookId() 方法  
   Book book = null;  
   BookDAO bookDAO = null;  
     
   bookDAO = new BookDAO();  
   book = bookDAO.selectBookByBookId(id);  
     
   ShoppingCartItem sci = null;  
   sci = new ShoppingCartItem (book);  
     
   sc.addNewItemToShoppingCart(sci);  
  }   
 }  
} 

(4)这段是 检查购物车是有对象的，这里单独拿出来是可以很好的在WEB开发中很好的进行重用 的。

public class MyBookStoreUtils {  
 private MyBookStoreUtils(){}  
   
 public static  ShoppingCart getShppingCartForCreateOrExist(HttpServletRequest request) {  
  ShoppingCart sc = null;  
  //2.1 检查在 HttpSession 对象中有没有购物车对象 , 即检查 session 中是否有 MyBookStoreConstants.SHOOPING_CART_KEY 属性  
  //   若 已经存在, 说明购物车存在, 直接取出  
  HttpSession session = null;  
  session = request.getSession();  
    
  Object obj = session.getAttribute (MyBookStoreConstants.SHOOPING_CART_KEY);  
    
  if(obj != null) {  
   sc = (ShoppingCart) obj;  
  }  
  //2.2 若不存在 MyBookStoreConstants.SHOOPING_CART_KEY 属性, 创建一个购物车对象, 并把该对象放入 Session 中   
  else{  
   sc = new ShoppingCart ();  
   session.setAttribute(MyBookStoreConstants.SHOOPING_CART_KEY, sc);  
  }  
    
  return sc;  
 }  
   
 public static  ShoppingCart getShppingCartForExist(HttpServletRequest request) {  
  ShoppingCart sc = null;  
  //2.1 检查在 HttpSession 对象中有没有购物车对象 , 即检查 session 中是否有 MyBookStoreConstants.SHOOPING_CART_KEY 属性  
  //   若 已经存在, 说明购物车存在, 直接取出  
  HttpSession session = null;  
  session = request.getSession();  
    
  Object obj = session.getAttribute (MyBookStoreConstants.SHOOPING_CART_KEY);  
    
  if(obj != null) {  
   sc = (ShoppingCart) obj;  
  }  
  //2.2 若不存在 MyBookStoreConstants.SHOOPING_CART_KEY 属性, 抛出异常, 提示用户还不存在购物车.  
  else {  
   throw new RuntimeException (MyBookStoreConstants.NO_SHOPPING_CART_EXCETPION);  
  }   
    
  return sc;  
 }  
} 

(5)这里是所有与购物车相关的SERVLET.

这个是更新数据的，需要在SERVICE中调用DAO的!

public class UpdateShoppingCartServlet extends HttpServlet {  
 
 public void doPost(HttpServletRequest request, HttpServletResponse response)   
   throws ServletException, IOException {  
  //获取表单信息   
  // request.getParameter(""); 方法行不通,　因为表单的　name 是随时变化的   
    
  //获取表单中的所有 name  
  Enumeration<String> nameEnums = request.getParameterNames();  
    
  Map items = new HashMap<String, Integer>();  
  //遍历 nameEnums, 再取出对应的 Value, 封装到 items 中   
    
  try {  
   while(nameEnums.hasMoreElements()) {  
    String bookId = nameEnums.nextElement();  
    String quantity = request.getParameter (bookId);  
      
    items.put(bookId, Integer.parseInt (quantity));  
   }  
  } catch (NumberFormatException e) {  
   // TODO Auto-generated catch block  
   e.printStackTrace ();  
   throw new RuntimeException (MyBookStoreConstants.QUANTITY_FORMAT_EXCEPTION);  
  }  
    
  //获 取购物车对象  
  ShoppingCart sc = null;  
  sc = MyBookStoreUtils.getShppingCartForExist(request);  
    
  //调用 Service 方法   
  BookService bookService = new BookService ();  
  bookService.updateShoppingCart(items, sc);  
    
  //派发页面 : showShoppingCart.jsp 页面  
  String forwardPage = "/WEB- INF/jsp/showShoppingCart.jsp";  
  request.getRequestDispatcher(forwardPage).forward (request, response);  
 }  
 
}  
 
public class ShowShoppingCartServlet extends HttpServlet {  
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)   
   throws ServletException, IOException {  
  //做一个转发   
  String forwardPage = null;  
    
  forwardPage = "/WEB- INF/jsp/showShoppingCart.jsp";  
    
  RequestDispatcher dispatcher = null;  
  dispatcher = request.getRequestDispatcher (forwardPage);  
  dispatcher.forward(request, response);  
 }  
 
}  
public class ReceiptServlet extends HttpServlet {  
 
 public void doPost(HttpServletRequest request, HttpServletResponse response)   
   throws ServletException, IOException {  
  //1. 获取表单信息: name 和 cardId  
    
  //2. 调用 Service 方法, 更新 books 表各条 book 的 saleAmount 字段   
    
  //2.1 获取购物车  
  ShoppingCart sc = MyBookStoreUtils.getShppingCartForExist(request);  
    
  BookService bookService = new BookService();  
  bookService.buyBooks (sc);  
    
  //2.1 使 Session 失效  
  HttpSession session = null;  
  session = request.getSession();  
  session.invalidate ();  
    
  //3. 派发页面: receipt.jsp 页面   
  request.getRequestDispatcher("/WEB-INF/jsp/receipt.jsp").forward(request, response);   
 }  
} 

这段我先开始很纳闷老师为什么会这样写呢，其实很简单，写个专门的转发的SERVLET这样，在每次转发的时候就只连接一个servlet比连接多个更来的简洁！提高了效率！

public class ForwardServlet extends HttpServlet {  
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)   
   throws ServletException, IOException {  
  //1. 获取 path  
  String path = request.getParameter("path");  
    
  //2. 派 发页面  
  request.getRequestDispatcher(path).forward(request, response);  
 }  
 
}  
public class DeleteShoppingCartItemServlet extends HttpServlet {  
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)   
   throws ServletException, IOException {  
  //1. 获取 id 号   
  String id = request.getParameter("bookid");  
    
  //2. 调用 BookService 方法 deleteShoppingCartItemById：, 进行删除操作  
  ShoppingCart sc = MyBookStoreUtils.getShppingCartForExist(request);  
    
  String bookTitle = sc.getBook(id).getTitle();  
    
  BookService bookService = new BookService ();  
  bookService.deleteShoppingCartItemById(id, sc);  
    
  //3. 派发页面  
  request.setAttribute(MyBookStoreConstants.DELETE_FROM_SHOPPING_CART_BOOK_TITLE, bookTitle);  
    
  String forwardPage = "/WEB- INF/jsp/showShoppingCart.jsp";  
  //4. 判断购物车是否为空,　若为空则派发到　emptyCart.jsp 页面  
  if(sc.getBooks().isEmpty())  
   forwardPage = "/WEB- INF/jsp/emptyCart.jsp";  
    
  RequestDispatcher dispatcher = null;  
  dispatcher = request.getRequestDispatcher (forwardPage);  
  dispatcher.forward(request, response);  
 }  
 } 

这里是清空购物车的SERVLET.

public class ClearShoppingCartServlet extends HttpServlet {  
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)   
   throws ServletException, IOException {  
  //1. 调用方法   
  BookService bookService = new BookService ();  
    
  ShoppingCart sc = null;  
  sc = MyBookStoreUtils.getShppingCartForExist (request);  
    
  bookService.clearShoppingCart (sc);  
    
  //2. 派发页面  
  String forwardPage = null;  
  forwardPage = "/WEB- INF/jsp/emptyCart.jsp";  
    
  RequestDispatcher dispatcher = request.getRequestDispatcher(forwardPage);  
  dispatcher.forward(request, response);  
 }  
 
}  
public class AddToShoppingCartServlet extends HttpServlet {  
 
 public void doGet(HttpServletRequest request, HttpServletResponse response)   
   throws ServletException, IOException {  
    
    
  //1. 获取书的 id 号  
  String bookId = null;  
  bookId = request.getParameter("bookId");  
    
  //2. 获取 购物车对象: 调用 getShppingCart 方法  
  ShoppingCart sc = null;  
  sc = MyBookStoreUtils.getShppingCartForCreateOrExist(request);  
    
  //3. 调用 Service 方法把 id 对应的 ShoppingCartItem 对象放入购物车 ShoppingCart 对象中： addToShoppingCart(id, shoppingCart);  
  BookService bookService = null;  
  bookService = new BookService();  
    
  bookService.addToShoppingCart(bookId, sc);  
    
  //4. 派发页面  
  String forwardPage = "/index.jsp";  
    
  //4.1 获取书名  
  String bookTitle = null;  
  //bookTitle = sc.getBooks().get(bookId).getBook().getTitle ();  
  bookTitle = sc.getBook(bookId).getTitle();  
    
  //4.2 将书 名放入请求域中, 以让页面进行显示  
  request.setAttribute (MyBookStoreConstants.ADD_TO_SHOPPING_CART_BOOK_TITLE, bookTitle);  
    
  RequestDispatcher dispatcher = null;  
  dispatcher = request.getRequestDispatcher (forwardPage);  
  dispatcher.forward(request, response);  
 }  
 
} 

(6)下面是显示层，对应着其相应的SERVLET.下面的JSP页面运用到了我们前段时间学的JSTL，EL表示.
'cashier.jsp'

1. <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"% >
3. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
4. <html>
5. <head>
6. <title>My JSP 'cashier.jsp' starting page</title>
7. </head>
9. <body>
10. <center>
11. <br><br>
12. 您一共购买 了 ${sessionScope.shoppingcartkey.totalQuantity} 本书
13. <br><br>
14. 您应付金额 是:${sessionScope.shoppingcartkey.totalPrice} 元。
15. <br><br>
16. <form action="receiptServlet" method="POST">
17. <table>
18. <tr>
19. <td>信用卡用户 名:</td>
20. <td><input type="text" name="userName"/></td>
21. </tr>
22. <tr>
23. <td>信用卡帐号:</td>
24. <td><input type="text" name="cardId"/></td>
25. </tr>
26. <tr align="center">
27. <td colspan="2">
28. <input type="submit" value="递交 "/>
29. </td>
30. </tr>
31. </table>
32. </form>
33. </center>
34. </body>
35. </html>
36. 'receipt.jsp'
37. <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
39. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
40. <html>
41. <head>
42. <title>My JSP 'emptyCart.jsp' starting page</title>
43. </head>
45. <body>
46. <center>
47. <br><br>
48. 您的购物车 为空<br><br>
49. <a href="${pageContext.request.contextPath }/index.jsp">继续购物<a>
50. </center>
51. </body>
52. </html>
53. <%@ page language="java" import="java.util.*" pageEncoding="UTF- 8"%>
55. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
56. <html>
57. <head>
58. <title>My JSP 'receipt.jsp' starting page</title>
59. </head>
61. <body>
62. 再见: ${param.userName }<br><br>
63. <a href="${pageContext.request.contextPath }/index.jsp">继续购物</a>&nbsp;&nbsp;
64. </body>
65. </html>
67. 'showShoppingCart.jsp'
68. <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"% >
69. <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
71. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
72. <html>
73. <head>
74. <title>My JSP 'showShoppingCart.jsp' starting page</title>
75. </head>
77. <body>
78. <center>
79. <c:if test="${requestScope.deleteToShoppingCartBookTitle != null}">
80. <br><br>
81. 您已经把 ${requestScope.deleteToShoppingCartBookTitle} 从购物车中删除了！
82. </c:if>
83. <br><br>
84. 您的购物车中一共有 ${sessionScope.shoppingcartkey.totalQuantity} 本书
85. <br><br>
86. <form action="updateShoppingCartServlet" method="POST">
87. <table cellpadding="10" cellspacing="0">
88. <tr>
89. <th>书名</th>
90. <th>价 格</th>
91. <th>数量 </th>
92. <td></td>
93. </tr>
94. <c:forEach items="${sessionScope.shoppingcartkey.books}" var="sci">
95. <tr>
96. <td>${sci.value.book.title }</td>
97. <td>${sci.value.book.price }</td>
98. <td><input type="text" value="${sci.value.quantity }" name="${sci.key }" size="2" /></td>
99. <td><a href="${pageContext.request.contextPath }/deleteShoppingCartItemServlet?bookid=${sci.key }">删除 </a></td>
100. <td></td>
101. </tr>
102. </c:forEach>
103. </table>
104. <input type="submit" value="保存修 改">
105. </form>
106. <br>
107. 总价格： ${sessionScope.shoppingcartkey.totalPrice}
108. <br><br>
109. <a href="${pageContext.request.contextPath }/index.jsp">继续购物 </a>&nbsp;&nbsp;
110. <a href="${pageContext.request.contextPath }/clearShoppingCartServlet">清空购物车 </a>&nbsp;&nbsp;
111. <a href="${pageContext.request.contextPath }/forwardServlet?path=cashier.jsp">付账 </a>
112. </center>
113. </body>
114. </html>

　　这样子简易JSP购物车算是完成了，当然这个JSP购物车只是简单的运用，没有涉及到大量的数据，作为入门的教学的例子是完全值得我们这些初学者消化的了!通过这次JSP购物车的联系，我对MVC的设计模式有了深刻的了解!不过其中的一些细节，还是需要我自己去慢慢的体会的!比如分页就是一个值得我去好好去研究的例子!