本篇内容介绍了“如何实现Javabean与JSP的购物车功能”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
成都创新互联公司是网站建设专家,致力于互联网品牌建设与网络营销，专业领域包括做网站、成都网站设计、电商网站制作开发、重庆小程序开发公司、微信营销、系统平台开发，与其他网站设计及系统开发公司不同，我们的整合解决方案结合了恒基网络品牌建设经验和互联网整合营销的理念，并将策略和执行紧密结合，且不断评估并优化我们的方案，为客户提供全方位的互联网品牌整合方案！
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 books = null; public ShoppingCart(){ books = new HashMap(); } public Map 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 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 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 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 items, ShoppingCart sc){ Set keySet = null; keySet = items.keySet (); for(Iterator 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 nameEnums = request.getParameterNames(); Map items = new HashMap(); //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'
