map介绍

//定义
Map<String, Double> map1 = new HashMap<String, Double>();
//存储
map1.put("苹果手机9", 7000.0);
//获值
map1.get("苹果手机9");

页面介绍

buy.jsp

复选框写出可选商品。

processbuy.jsp

1、传入map，如果为空，则初始化为0

2、获取选择的物品

3、循环，置物品的购买数量

4、把数量保存到session

5、转发到show.jsp

show.jsp

显示购买的物品数量，以及价格。

源代码

buy.jsp

<h2 align="center">商品列表</h2>
    <div align="center">
      <form action="processbuy.jsp" method="post">
        <table border="0" cellspacing="30">
          <tr>
            <th>商品名称</th>
            <th>购买</th>
            <th>价格</th>
          </tr>
          <tr>
          	<td>笔记本</td>
            <td><input type="checkbox" name="item" value="computer"></td>
            <td>￥5000</td>
          </tr>
          <tr>
          	<td>汽车</td>
            <td><input type="checkbox" name="item" value="car"></td>
            <td>￥200000</td>
          </tr>
          <tr>
          	<td>香水</td>
            <td><input type="checkbox" name="item" value="flower"></td>
            <td>￥500</td>
          </tr>
          <tr>
          	<td>书籍</td>
            <td><input type="checkbox" name="item" value="book"></td>
            <td>￥20</td>
          </tr>
		</table>
		
		<input type="submit" value="购买">      
      </form>
    </div>

processbuy.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

	request.setCharacterEncoding("utf-8");
	
	Map<String, Integer> map1 = (Map<String, Integer>)session.getAttribute("map1");
	if(map1 == null){
		map1 = new HashMap<String, Integer>();
		map1.put("笔记本", 0);
		map1.put("汽车", 0);
		map1.put("香水", 0);
		map1.put("书籍", 0);
	}
	
	String[] buys = request.getParameterValues("item");
	
	for(String item:buys){
		if(item.equals("computer")){
			int num1 = map1.get("笔记本").intValue();
			map1.put("笔记本", num1+1);
		}
		else if(item.equals("car")){
			int num2 = map1.get("汽车").intValue();
			map1.put("汽车", num2+1);
		}
		else if(item.equals("flower")){
			int num3 = map1.get("香水").intValue();
			map1.put("香水", num3+1);
		}
		else{
			int num4 = map1.get("书籍").intValue();
			map1.put("书籍", num4+1);
		}
	}

	session.setAttribute("map1", map1);
	request.getRequestDispatcher("show.jsp").forward(request, response);
%>

show.jsp

    <div align="center">
      <h2>结算</h2>
      <%
    	Map<String, Integer> map1 = (Map<String, Integer>)session.getAttribute("map1");
      %>
      	
      	<table border="0" cellspacing="30">
          <tr>
            <th>商品名称</th>
            <th>数量</th>
            <th>总价</th>
          </tr>
          <tr>
          	<td>笔记本</td>
            <td><%=map1.get("笔记本") %></td>
            <td><%=map1.get("笔记本") %>*5000</td>
          </tr>
          <tr>
          	<td>汽车</td>
            <td><%=map1.get("汽车")%></td>
            <td><%=map1.get("汽车")%>*200000</td>
          </tr>
          <tr>
          	<td>香水</td>
            <td><%=map1.get("香水")%></td>
            <td><%=map1.get("香水")%>*500</td>
          </tr>
          <tr>
          	<td>书籍</td>
            <td><%=map1.get("书籍") %></td>
            <td><%=map1.get("书籍") %>*20</td>
          </tr>
		</table>
		<p>总金额：<%=map1.get("笔记本")*5000+map1.get("汽车")*200000+map1.get("香水")*500+map1.get("书籍")*20 %></p>
		<p><a href="buy.jsp">继续购买</a></p>
    </div>