jsp+servlet实现商城购物车功能

<a href="AddCart?id=${b.id}"><button class="btn btn-default">加入购物车<span class="glyphicon glyphicon-shopping-cart"></span></button></a>

商品详情页选中“加入购物车”后跳到AddCart

public class AddCart extends HttpServlet {
	
   
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String id=request.getParameter("id");
		ProductService ps=new ProductService();
		Book b=ps.findBookById(id);
		HttpSession session=request.getSession();
		//从session中获取购物车对象
		Map<Book,Integer> cart=(Map<Book,Integer>)session.getAttribute("cart");
		//如果购物车为空，说明没有商品存储在购物车中，创建除购物车
		if(cart==null) {
			cart=new HashMap<Book,Integer>() ;	
		}
		//向购物车添加商品数量信息
		Integer count=cart.put(b, 1);
		//如果商品数量不为空，则商品数量+1，否则添加新的商品信息
		if(count!=null) {
			cart.put(b, count+1);
		}  
		session.setAttribute("cart", cart);
		request.getRequestDispatcher("cart.jsp").forward(request, response);;
	
	}

	
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		doGet(request, response);
	}

}

以map集合存储Book对象还有购买数量，并且新建购物车，存进session中

 <script type="text/javascript">
		function changeNum(id,num,totalCount){
			num = parseInt(num);
			totalCount =parseInt(totalCount);
			if(num<1){
				if(confirm("是否确认要删除此商品？")){
					num = 0;
				}else{
					num=1;
				}
			}
			
			if(num>totalCount){
				alert("购买数量不能大于库存数量！");
				num=totalCount;
			}
			location.href="${pageContext.request.contextPath}/ChangeNumServlet?id="+id+"&num="+num;
		}
	    </script>

 

<table cellpadding="1" style="width: 80%; height: auto;border:1px #8B0000 solid;text-align:center;margin-left:150px;">
			<tr>
				<td width="10%"> 序号</td>
				<td width="30%"> 商品名称</td>
				<td width="10%">价格</td>
				<td width="20%"> 数量</td>
				<td width="10%">库存</td>
				<td width="10%">小计</td>
				<td width="10%">取消</td>
			</tr>
		</table>
		<!-- 循环输出商品信息 -->
		  <c:set var="total" value="0"/>
		 <c:forEach items="${cart}" var="entry" varStatus="vs">
		 <table width="80%" border="0" cellspacing="0" style="margin-left:150px;text-align:center">
		   <tr>
		       <td width="10%">${vs.count}</td>
		       <td width="30%">${entry.key.name}</td>
		       <td width="10%">${entry.key.price }</td>
		       <td width="20%">
		           <!-- 减少商品数量 -->
		           、               <input type="button" value='-' style="width:20px" onclick="changeNum('${entry.key.id}','${entry.value-1 }','${entry.key.pnum }')">
		           <!-- 商品数量显示 -->
		           <input name="text" type="text" value="${entry.value}" style="width:40px;text-align:center">
		           <!-- 添加商品数量 -->
		           <input type="button" value='+' style="width:20px" onclick="changeNum('${entry.key.id}','${entry.value+1 }','${entry.key.pnum }')">        
		       </td>
		       <td width="10%">${entry.key.pnum}</td>
		       <td width="10%">${entry.key.price*entry.value}</td>
		       <td width="10%">
		          <!-- 删除商品 -->
		          、            <a href="ChangeNumServlet?id=${entry.key.id}&num=0" style="color: #FF0000; font-weight: bold">X</a>
               </td>
		    </tr>
		 </table>
		 <c:set value="${total+ entry.key.price*entry.value}" var="total"/>
		 </c:forEach>
		 <br>
		<!-- 合计信息 -->
		<table style="margin-left:1000px">
		    <tr>
	            <td><font style="color: #FF6600; font-weight: bold">合计：  ${total}元</font>
	            </td>
	        </tr>
		</table>
		<br>
		<br>
		<br>
		<div style="padding-left:690px;">
           <a href="index.jsp"><button class="btn btn-info">继续购物</button></a>
           <a href="order.jsp"><button class="btn btn-default">立即买单</button></a>
           </div>	

public class ChangeNumServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String id = request.getParameter("id");
		int num = Integer.parseInt(request.getParameter("num"));
		
		HttpSession session = request.getSession();
		Map<Book, Integer> cart = (Map<Book, Integer>) session.getAttribute("cart");
		ProductService ps=new ProductService();
		Book b=ps.findBookById(id);
		//如果商品数据为0，就删除对象
		if(num==0) {
			cart.clear();
		}else {
			cart.clear();
			cart.put(b, num);
		}
       
		request.getRequestDispatcher("cart.jsp").forward(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

通过id找到对应的book对象后，从session中取出集合，要先清空集合再重新存键值（书和购买数量进去），不清空就会导致一会的cart页面出现多行从购物车里遍历取出来的数据