Java基礎99 把商品加入購物車中及刪除操做（Servlet技術，簡單演示，只是把購物車添加到session中，不是以數據庫的形式存儲）把購物車中的商品購買支付、生成訂單（Servlet技術，簡單

時間 2019-12-08

標籤 java 基礎商品加入購物車刪除 servlet 技術簡單演示只是添加 session 不是數據庫形式存儲購買支付生成訂單欄目 Java 简体版

原文原文鏈接

一、創建購物車實體類

Cart 類 //實體類
javascript

 1 package com.shore.entity;
 2 
 3 import java.util.HashMap;
 4 import java.util.Map;
 5 
 6 /**
 7  * @author DSHORE/2019-5-16
 8  *
 9  */
10 public class Cart {
11     //Map集合中，可能有不少本書
12     private Map<String, CartItem> items = new HashMap<String, CartItem>();//key:購物項對應的書的id  value：購物項
13     private int num;//購物車中，書籍的數量
14     private float price;//總價,付款時的金額
15     
16     public Map<String, CartItem> getItems() {
17         return items;
18     }
19     
20     public int getNum() {
21         num = 0;
22         for(Map.Entry<String, CartItem> me:items.entrySet()){
23             num += me.getValue().getNum();
24         }
25         return num;
26     }
27     /*public void setNum(int num) {//不能設置書籍的數量
28         this.num = num;
29     }*/
30     public float getPrice() {
31         price = 0;
32         for(Map.Entry<String, CartItem> me:items.entrySet()){
33             price += me.getValue().getPrice();
34         }
35         return price;
36     }
37     /*public void setPrice(float price) {//不能設置價格
38         this.price = price;
39     }*/
40 
41     //把商品加入購物車
42     public void addCart(Book book) {//同一本書，可購買了多本
43         if(items.containsKey(book.getId())){
44             //有這本書的id（當同一本書，我購買兩本或更多本時，保持其餘字段的屬性不變，只增長數量）
45             CartItem item = items.get(book.getId());
46             item.setNum(item.getNum() + 1);//其餘不改變，只增長數量
47         }else{
48             //沒有這本書的id
49             CartItem item = new CartItem();
50             item.setBook(book);
51             item.setNum(1);
52             items.put(book.getId(), item);
53         }
54     }
55 
56     //刪除購物車中的商品（同一種商品，有多個時，則是減小該商品的數量）
57     public void deleteCartByBook(String bookId) {
58         CartItem item = items.get(bookId);
59         if (item.getNum() > 1) {//購物車中，同一商品，購買了多件，則每刪除一次，該商品的數量就減一次（價格自動減小） 60             item.setNum(item.getNum() - 1);//其餘不改變，只減小數量
61         }else {
62             items.remove(bookId);
63         }
64     }
65 }

CartItem 類 //購物項類html

 1 package com.shore.entity;
 2 
 3 /**
 4  * @author DSHORE/2019-5-16
 5  *
 6  */
 7 public class CartItem {//購物項
 8     private Book book;
 9     private int num;
10     private float price;
11     
12     public Book getBook() {
13         return book;
14     }
15     public void setBook(Book book) {
16         this.book = book;
17     }
18     public int getNum() {
19         return num;
20     }
21     public void setNum(int num) {
22         this.num = num;
23     }
24     public float getPrice() {
25         return num*book.getPrice();//計算出同一本書的總價（或同一類書）
26     }
27     /*public void setPrice(float price) {//不能設置價格
28         this.price = price;
29     }*/
30 }

二、創建Servlet類

ClientServlet 類前端

 1 package com.shore.web.controller.client;
 2 
 3 import java.io.IOException;
 4 import java.util.List;
 5 
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 import javax.servlet.http.HttpSession;
11 
12 import com.shore.entity.Book;
13 import com.shore.entity.Cart;
14 import com.shore.entity.CartItem;
15 import com.shore.service.BookService;
16 import com.shore.service.impl.BookServiceImpl;
17 
18 /**
19  * @author DSHORE/2019-5-12
20  *
21  */
22 public class ClientServlet extends HttpServlet {
23     private static final long serialVersionUID = 1L;//序列化
24     BookService bService = new BookServiceImpl();
25 
26     public void doGet(HttpServletRequest request, HttpServletResponse response)
27             throws ServletException, IOException {
28         String operation = request.getParameter("operation");
29         if ("addCartByBook".equals(operation)){
30             addCartByBook(request,response);
31         }else if("deleteCartByBook".equals(operation)){
32             deleteCartByBook(request,response);
33         }
34     }
35 
36     //刪除購物車中的商品（同一種商品，有多個時，則是減小該商品的數量）
37     private void deleteCartByBook(HttpServletRequest request,
38             HttpServletResponse response) throws ServletException, IOException {
39         //獲取數的id
40         String bookId = request.getParameter("bookId");
41         //從HttpSession中取出購物車
42         HttpSession session = request.getSession();
43         Cart cart = (Cart)session.getAttribute("cart");
44         cart.deleteCartByBook(bookId); //直接調用 實體類Cart中的deleteCartByBook()方法 45         /*//提示刪除商品成功
46         request.setAttribute("message","<script type='text/javascript'>alert('刪除商品成功')</script>");*/
47         request.getRequestDispatcher("/client/showCart.jsp").forward(request, response);
48     }
49 
50     //購買書籍（把要購買的商品加入購物車）
51     private void addCartByBook(HttpServletRequest request,
52             HttpServletResponse response) throws ServletException, IOException {
53         //獲取數的id
54         String bookId = request.getParameter("bookId");
55         //獲取要購買的書
56         Book book = bService.findBookById(bookId);
57         //從HttpSession中取出購物車
58         HttpSession session = request.getSession();
59         Cart cart = (Cart)session.getAttribute("cart");
60         //沒有:建立購物車,並放入到HttpSession中(購物車的car)
61         if(cart == null){
62             cart = new Cart();
63             session.setAttribute("cart",cart);
64         }
65         //有：把書放到購物車中
66         cart.addCart(book);//直接調用 實體類Cart中的addCart()方法 67         //提示加入購物車成功
68         request.setAttribute("message","<script type='text/javascript'>alert('加入購物車成功，請前去付款!')</script>");
69         request.getRequestDispatcher("/index.jsp").forward(request, response);
70     }
71 
72     public void doPost(HttpServletRequest request, HttpServletResponse response)
73             throws ServletException, IOException {
74         doGet(request, response);
75     }
76 }

三、前端頁面

showCart.jsp 購物車的頁面（簡單測試，頁面隨意搞搞的，還看得過去吧）java

 1 <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
 2 <%@include file="/client/header.jsp"%>
 3 <style> 
 4     table tr th{ border:1px solid #C1C1C1; font-size: 16px;}
 5     table,table tr td { border:1px solid #C1C1C1; }
 6     table { width: 71%; min-height: 25px; line-height: 25px; border-collapse: collapse; padding:2px; margin:auto;text-align: center;}
 7 </style> 
 8 
 9 <h2 style="text-align: center;font-size: 20px">您購買的商品以下</h2>
10    <c:if test="${empty sessionScope.cart.items}">
11     <!-- 若是購物車爲空（沒商品），則顯示這張圖片，提示「購物車空空如也」 -->
12      <img height="432" width="720" src="${pageContext.request.contextPath}/images/0.jpg"/>
13  </c:if>
14  <c:if test="${!empty sessionScope.cart.items}">
15      <table>
16          <tr>
17              <th>書名</th>
18              <th>做者</th>
19              <th>單價</th>
20              <th>數量</th>
21              <th>小計</th>
22              <th>操做</th>
23          </tr>
24          <c:forEach items="${sessionScope.cart.items}" var="me">
25              <tr>
26               <td>${me.value.book.name}</td>
27               <td>${me.value.book.author}</td>
28               <td>${me.value.book.price}</td>
29               <td>${me.value.num}</td>
30               <td>${me.value.price}</td>
31               <td>
32                   <a href="${pageContext.request.contextPath}/ClientServlet?operation=deleteCartByBook&bookId=${me.value.book.id}">刪除</a>
33               </td>
34           </tr>
35          </c:forEach>
36          <tr>
37              <td colspan="6" align="right">
38                  總數量：${sessionScope.cart.num}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
39                  應付款總金額:${sessionScope.cart.price}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
40                  <a href="${pageContext.request.contextPath}/ClientServlet?operation=genOrders" style="text-decoration: none;font-weight: bold;">付款購買</a>
41                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
42              </td>
43          </tr>
44      </table>
45  </c:if>
46 ${message}