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购物车相关···

2010-10-03 22:01 267 查看

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'

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

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

<html>

<head>

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

</head>

<body>

<center>

<br><br>

您一共购买了 ${sessionScope.shoppingcartkey.totalQuantity} 本书

<br><br>

您应付金额是:${sessionScope.shoppingcartkey.totalPrice} 元。

<br><br>

<form action="receiptServlet" method="POST">

<table>

<tr>

<td>信用卡用户名:</td>

<td><input type="text" name="userName"/></td>

</tr>

<tr>

<td>信用卡帐号:</td>

<td><input type="text" name="cardId"/></td>

</tr>

<tr align="center">

<td colspan="2">

<input type="submit" value="递交 "/>

</td>

</tr>

</table>

</form>

</center>

</body>

</html>

'receipt.jsp'

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

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

<html>

<head>

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

</head>

<body>

<center>

<br><br>

您的购物车为空<br><br>

<a href="${pageContext.request.contextPath }/index.jsp">继续购物<a>

</center>

</body>

</html>

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

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

<html>

<head>

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

</head>

<body>

再见: ${param.userName }<br><br>

<a href="${pageContext.request.contextPath }/index.jsp">继续购物</a>

</body>

</html>

'showShoppingCart.jsp'

<%@ 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 'showShoppingCart.jsp' starting page</title>

</head>

<body>

<center>

<c:if test="${requestScope.deleteToShoppingCartBookTitle != null}">

<br><br>

您已经把 ${requestScope.deleteToShoppingCartBookTitle} 从购物车中删除了！

</c:if>

<br><br>

您的购物车中一共有 ${sessionScope.shoppingcartkey.totalQuantity} 本书

<br><br>

<form action="updateShoppingCartServlet" method="POST">

<table cellpadding="10" cellspacing="0">

<tr>

<th>书名</th>

<th>价格</th>

<th>数量 </th>

<td></td>

</tr>

<c:forEach items="${sessionScope.shoppingcartkey.books}" var="sci">

<tr>

<td>${sci.value.book.title }</td>

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

<td><input type="text" value="${sci.value.quantity }" name="${sci.key }" size="2" /></td>

<td><a href="${pageContext.request.contextPath }/deleteShoppingCartItemServlet?bookid=${sci.key }">删除 </a></td>

<td></td>

</tr>

</c:forEach>

</table>

<input type="submit" value="保存修改">

</form>

<br>

总价格： ${sessionScope.shoppingcartkey.totalPrice}

<br><br>

<a href="${pageContext.request.contextPath }/index.jsp">继续购物 </a>

<a href="${pageContext.request.contextPath }/clearShoppingCartServlet">清空购物车 </a>

<a href="${pageContext.request.contextPath }/forwardServlet?path=cashier.jsp">付账 </a>

</center>

</body>

</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!

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