servlet练习，简易购物车

首先，我们创建一个数据库shopping,并插入几条记录（）因为这个练习是用来练习servlet，所以我们用session来存值，并没有在数据库创建用户表和购物车表

use master
go
if exists (select * from sysdatabases where name='shopping')
	drop database shopping
--创建数据库
create database shopping
use shopping
--创建商品表
create table shop
(
shopId int identity(1,1),
shopName varchar(20) not null,
price money 
)
--添加商品
insert into shop 
select '魔界剑圣异界纵横',360 union all
select '斗破苍穹',360 union all
select '武动乾坤',250 union all
select '大主宰',260 union all
select '元尊',180

然后我们开始写java代码，项目的主题构造如下：

创建底层的链接数据库方法（BaseDao.java），我这里把增删改查的方法给抽出来了一写他们都有的代码，这样写方法时就会省事

package com.ruanyuan.Dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class BaseDao {
	//驱动
	private static final String DRIVER="com.microsoft.sqlserver.jdbc.SQLServerDriver";
	//数据库的URL
	private static final String URL="jdbc:sqlserver://localhost:1433;DatabaseName=Shopping";
	//数据库的用户名
	private static final String USERNAME="sa";
	//数据库的密码
	private static final String PASSWORD="sa";
	//连接对象
	protected Connection conn;
	//预编译PreparedStatement对象
	protected PreparedStatement pstmt;
	//结束集ResultSet对象
	protected ResultSet rs;
	
	// 数据库连接
	protected void getConnection() {
		try {
			// 注册sql驱动
			Class.forName(DRIVER);
			// 加载驱动并且得到连接对象
			conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
		} catch (ClassNotFoundException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}

	}
	// 释放资源
	protected void closeResource() {
		if (rs != null) {
			try {
				rs.close();// 释放结果集
			} catch (SQLException e) {
				// TODO 自动生成的 catch 块
				e.printStackTrace();
			}
		}
		if (pstmt != null) {
			try {
				pstmt.close();// 释放预编译的命令对象
			} catch (SQLException e) {
				// TODO 自动生成的 catch 块
				e.printStackTrace();
			}
		}
		if (conn != null) {
			try {
				conn.close();// 释放连接对象
			} catch (SQLException e) {
				// TODO 自动生成的 catch 块
				e.printStackTrace();
			}
		}

	}

	/**
	 * 增 删 改 的通用方法
	 * @param sql
	 * @param paras
	 * @return
	 */
	protected int execUpdate(String sql, String[] paras) {
		int count = 0;// 受影响的行数
		try {
			// 连接数据库
			this.getConnection();
			// 基于sql语句构建PreparedStatement对象
            pstmt=conn.prepareStatement(sql);
			// 遍历参数数组，并将值赋给PrepareStatement对象
			if (paras != null && paras.length > 0) {
				for (int i = 0; i < paras.length; i++) {
					pstmt.setString(i + 1, paras[i]);

				}
			}
			// 执行SQL语句
			count = pstmt.executeUpdate();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			this.closeResource();
		}
		return count;
	}

/**
	 * 查询 的通用方法
	 */
	protected ResultSet execQuery(String sql,String[] paras){
		   
		try {
			//连接数据库
			this.getConnection();
			//基于SQL语句创建PreparedStantment对象
			pstmt = conn.prepareStatement(sql);
			//将SQL语句参数数组中的值依次赋给预执行语句
			if(paras!=null&¶s.length>0){
				for (int i = 0; i < paras.length; i++) {
					pstmt.setString(i + 1, paras[i]);


				}
			}
			//执行SQL语句
			rs = pstmt.executeQuery();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		//返回结果集
		return rs;
	}

接下来我们封装一个shop类

package com.ruanyuan.entity;

public class Shop {
	private int shopId;
	private String shopName;
	private int price;
	private int count;
	public int getShopId() {
		return shopId;
	}
	public void setShopId(int shopId) {
		this.shopId = shopId;
	}
	public String getShopName() {
		return shopName;
	}
	public void setShopName(String shopName) {
		this.shopName = shopName;
	}
	public int getPrice() {
		return price;
	}
	public void setPrice(int price) {
		this.price = price;
	}
	public int getCount() {
		return count;
	}
	public void setCount(int count) {
		this.count = count;
	}
	
}

然后我们开始写方法，我们在一进入网页时，需要展示所有商品，在购买后跳转到购物车界面，我们需要根据商品id查询出购买的商品名称

代码如下：（从代码可以看出，我们继承了连接数据库的BaseDao,在写每个方法时，我们调用父类的方法super.来调用）

package com.ruanyuan.Dao;

import java.util.ArrayList;
import java.util.List;

import com.ruanyuan.entity.Shop;

public class ShopDao extends BaseDao {
	//all商品
	public List<Shop> allshop(){
		String sql="select * from shop";
		List<Shop> list =new ArrayList<Shop>();
		try {
			super.execQuery(sql, null);
			while(rs.next()){
				Shop shop = new Shop();
				shop.setShopId(rs.getInt("shopId"));
				shop.setPrice(rs.getInt("price"));
				shop.setShopName(rs.getString("shopName"));
				list.add(shop);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally{super.closeResource();}
		return list;
		
	}
	//id查找
	public Shop searchById(int shopId){
		Shop shop=new Shop();
		String sql="select * from shop where shopId=?";
		String[] paras={String.valueOf(shopId)};
		try {
			super.execQuery(sql, paras);
			if(rs.next()){
				shop.setShopId(rs.getInt("shopId"));
				shop.setPrice(rs.getInt("price"));
				shop.setShopName(rs.getString("shopName"));
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return shop;
	}
}

然后我们搭建页面，index.jsp，这里我们用了java小脚本，也是为了方便，没有再写成servlet

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page import="com.ruanyuan.Dao.*"%>
<%@ page import="com.ruanyuan.entity.*"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
	<style type="text/css">
	.float_ul{
		list-style-type: none;
	}
	ul li{
		float: left;
		padding-left: 10px;
		line-height: 20px;
		text-align: center;
		width: 100px;
	}
	</style>
  </head>
  <%
  	ShopDao shopdao = new ShopDao();
  	List<Shop> list=shopdao.allshop();
  	request.setAttribute("list",list);
   %>
  <body>
  
    	<ul class="float_ul">
    		<li>商品编号</li>
    		<li>商品名称</li>
    		<li>单价</li>
    		<li>购买数量</li>
    		<li>操作</li>
    	</ul>
    	<div style="clear: both;" ></div>
    	<c:forEach var="shop" items="${list}">
    	<form action="shopservlet" method="post">
    		<ul class="float_ul">
    			<li>${shop.shopId }<input type="hidden" value="${shop.shopId }" name="itemID"/></li>
    			<li>${shop.shopName }</li>
    			<li>${shop.price }</li>
    			<li><input type="text" name="ShopCount" value="" style="width: 50px;"/></li>
    			<li><input type="submit" value="加入购物车"/></li>
		   	</ul>
		   	<div style="clear: both;" ></div>
		 </form>
    	</c:forEach>
    
    <input type="button" value="结算" onclick="location.href='account.jsp'">
  </body>
</html>

运行界面如下：

当我们输入购买数量，点击加入购物车时，会跳转到shopservlet，（这里我们需要存商品id，和商品信息，所以我们用了HsahMap）

public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		ShopDao shopdao = new ShopDao();
		int itemID=Integer.parseInt(request.getParameter("itemID"));//获取商品id
		int buyCount=Integer.parseInt(request.getParameter("ShopCount"));//获取商品购买数量
		HttpSession session = request.getSession();//创建一个session
		HashMap<Integer, Shop> shopCart = null;
		if(session.getAttribute("SelectedGoods")==null){//判断是否第一次跳转到servlet
			shopCart = new HashMap<Integer,Shop>();
		}else{
			shopCart = (HashMap<Integer,Shop>) session.getAttribute("SelectedGoods");
		}
		//判断购物车中是否存在已经购买的商品，如果存在，则只增加数据，否则添加新的购买条目
		if(shopCart.containsKey(itemID)){
			int oldCount = (Integer)shopCart.get(itemID).getCount();
			Shop shop=shopdao.searchById(itemID);
			shop.setCount(oldCount+buyCount);
			shopCart.put(itemID, shop);
		}else{
			Shop shop=shopdao.searchById(itemID);
			shop.setCount(buyCount);
			shopCart.put(itemID, shop);
		}
		//将购买的商品保存到session
		session.setAttribute("SelectedGoods", shopCart);
		response.sendRedirect("index.jsp");//重定向到index.jsp
	}

当我们点击结算时，跳转到account.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
  </head>
  <body> 
    session id:<%=session.getId() %><br/>
    <c:if test="${empty sessionScope.SelectedGoods}">
    	<h1>未购买任何商品</h1>
    </c:if>
    <c:if test="${not empty sessionScope.SelectedGoods}">
    	购物车有以下商品<br/>
    	<c:set var="total" value="0"></c:set>
    	<table border="1">
    		<tr><td>编号</td><td>名称</td><td>数量</td><td>金额</td></tr>
    		<c:forEach items="${sessionScope.SelectedGoods}" var="good">
    				<tr><td>${good.key}</td><td>${good.value.shopName }</td><td>${good.value.count}</td><td>${good.value.count*good.value.price }</td></tr>
    				<c:set var="total" value="${total+good.value.count*good.value.price }"></c:set>
    		</c:forEach>
    	</table>
    </c:if>
    总金额：${total }
    <a href="index.jsp">继续购买</a>
  </body>
</html>

现在我们每个商品各买了一次，结算界面如下：