浅谈MVC(jsp+servlet+JavaBean简单实例)

MVC（Model View Controller) 旨在分离模型、控制、视图。是一种分层思想的体现。

项目实例：购物车商品管理

总体设计

1实现DBHelper类
2创建实体类
3创建业务逻辑类(DAO)
4创建控制层
5创建页面层

---

1数据库连接

package util;

import java.sql.*;

public class DBHelper {

public DBHelper() {
// TODO Auto-generated constructor stub
    }
private static final String driver="com.mysql.jdbc.Driver";
private static final String url="jdbc:mysql://localhost:3306/shopping";
private static final String username="root";
private static final String password="123";

private static Connection con;
//加载驱动
static
    {
try{
            Class.forName(driver);
        }catch (Exception e) {
            e.printStackTrace( );
        }
    }


//单例模式返回数据库对象
public static Connection getConnection() throws Exception {
if(con==null){
            con=DriverManager.getConnection(url,username,password);
return con;
    }
return con;
    }
public static void main(String[] args) {
try {
            Connection con=DBHelper.getConnection();
if(con!=null){
                System.out.println("连接正常！");
            }else{
                System.out.println("连接异常！");
            }
        } catch (Exception e) {
// TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

---

2实体类

• 商品类

package entity;

public class Items {

private int id;
private String name;
private String city;
private int price;
private int number;
private String picture;

public Items() {

    }

public Items(int id, String name, String city, int price, int number, String picture) {

this.id = id;
this.name = name;
this.city = city;
this.price = price;
this.number = number;
this.picture = picture;
    }

public int getId() {
return id;
    }

public void setId(int id) {
this.id = id;
    }

public String getName() {
return name;
    }

public void setName(String name) {
this.name = name;
    }

public String getCity() {
return city;
    }

public void setCity(String city) {
this.city = city;
    }

public int getPrice() {
return price;
    }

public void setPrice(int price) {
this.price = price;
    }

public int getNumber() {
return number;
    }

public void setNumber(int number) {
this.number = number;
    }

public String getPicture() {
return picture;
    }

public void setPicture(String picture) {
this.picture = picture;
    }

@Override
public int hashCode() {
// TODO Auto-generated method stub
return this.getId() + this.getName().hashCode();
    }

@Override
public boolean equals(Object obj) {
// TODO Auto-generated method stub
if (this == obj) {
return true;
        }
if (obj instanceof Items) {
            Items i = (Items) obj;
if (this.getId() == i.getId() && this.getName().equals(i.getName())) {
return true;
            } else {
return false;
            }

        } else {
return false;
        }
    }

@Override
public String toString() {

return "商品编号" + this.getId() + ",商品名称" + this.getName();
    }

}

• 购物车类

package entity;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;



//购物车类
public class Cart {

// 购买商品集合
private HashMap<Items, Integer> goods;

// 购物车总金额
private double totalPrice;


public Cart() {

        goods = new HashMap<Items, Integer>();
        totalPrice = 0.0;
    }

public HashMap<Items, Integer> getGoods() {
return goods;
    }

public void setGoods(HashMap<Items, Integer> goods) {
this.goods = goods;
    }

public double getTotalPrice() {
return totalPrice;
    }

public void setTotalPrice(double totalPrice) {
this.totalPrice = totalPrice;
    }
//添加商品
public boolean addGoodsInCart(Items item,int number){

if(goods.containsKey(item)){
            goods.put(item, goods.get(item)+number);
        }else{
            goods.put(item, number);
        }


        calTotalPrice();//重新计算购物车总金额
return true;
    }
//删除
public boolean removeGoodsFromCart(Items item){
        goods.remove(item);
return true;
    }
//统计总金额
public double calTotalPrice(){
double sum=0.0;
        Set<Items> keys= goods.keySet();//获得键集合
        Iterator<Items> it=keys.iterator();//获得迭代器对象
while(it.hasNext()){
            Items i= it.next();
            sum +=i.getPrice()* goods.get(i);
        }
this.setTotalPrice(sum);//设置购物车总金额
return this.getTotalPrice();
    }
//测试购物车类
public static void main(String[] args) {

//创建两个商品对象
        Items i1 =new Items(1,"沃特篮球鞋","温州",200,500,"001.jpg");
        Items i2 =new Items(2,"李宁篮球鞋","广州",300,500,"002.jpg");
        Items i3 =new Items(2,"李宁篮球鞋","广州",300,500,"002.jpg");
        Cart c=new Cart();
        c.addGoodsInCart(i1, 1);
        c.addGoodsInCart(i2, 2);
//再次购买李宁 三双
        c.addGoodsInCart(i3, 3);
//遍历购物商品集合
        Set<Map.Entry<Items, Integer>> items=c.getGoods().entrySet();
for(Map.Entry<Items, Integer> obj:items){

            System.out.println(obj);
        }
        System.out.println("总金额"+c.getTotalPrice());
    }
}

DAO层（javabean）

package dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;

import util.DBHelper;

import entity.Items;

//商品的业务逻辑类
public class ItemsDAO {

// 获得所有的商品信息
public ArrayList<Items> getAllItems() {
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
        ArrayList<Items> list = new ArrayList<Items>(); // 商品集合
try {
            conn = DBHelper.getConnection();
            String sql = "select * from items;"; // SQL语句
            stmt = conn.prepareStatement(sql);
            rs = stmt.executeQuery();
while (rs.next()) {
                Items item = new Items();
                item.setId(rs.getInt("id"));
                item.setName(rs.getString("name"));
                item.setCity(rs.getString("city"));
                item.setNumber(rs.getInt("number"));
                item.setPrice(rs.getInt("price"));
                item.setPicture(rs.getString("picture"));
                list.add(item);// 把一个商品加入集合
            }
return list; // 返回集合。
        } catch (Exception ex) {
            ex.printStackTrace();
return null;
        } finally {
// 释放数据集对象
if (rs != null) {
try {
                    rs.close();
                    rs = null;
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
// 释放语句对象
if (stmt != null) {
try {
                    stmt.close();
                    stmt = null;
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        }

    }

// 根据商品编号获得商品资料
public Items getItemsById(int id) {
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
try {
            conn = DBHelper.getConnection();
            String sql = "select * from items where id=?;"; // SQL语句
            stmt = conn.prepareStatement(sql);
            stmt.setInt(1, id);
            rs = stmt.executeQuery();
if (rs.next()) {
                Items item = new Items();
                item.setId(rs.getInt("id"));
                item.setName(rs.getString("name"));
                item.setCity(rs.getString("city"));
                item.setNumber(rs.getInt("number"));
                item.setPrice(rs.getInt("price"));
                item.setPicture(rs.getString("picture"));
return item;
            } else {
return null;
            }

        } catch (Exception ex) {
            ex.printStackTrace();
return null;
        } finally {
// 释放数据集对象
if (rs != null) {
try {
                    rs.close();
                    rs = null;
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
// 释放语句对象
if (stmt != null) {
try {
                    stmt.close();
                    stmt = null;
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }

        }
    }
//获取最近浏览的前五条商品信息
public ArrayList<Items> getViewList(String list)
    {
        System.out.println("list:"+list);
        ArrayList<Items> itemlist = new ArrayList<Items>();
int iCount=5; //每次返回前五条记录
if(list!=null&&list.length()>0)
        {
            String[] arr = list.split("#");
            System.out.println("arr.length="+arr.length);
//如果商品记录大于等于5条
if(arr.length>=5)
            {
for(int i=arr.length-1;i>=arr.length-iCount;i--)
               {
                  itemlist.add(getItemsById(Integer.parseInt(arr[i])));  
               }
            }
else
            {
for(int i=arr.length-1;i>=0;i--)
                {
                    itemlist.add(getItemsById(Integer.parseInt(arr[i])));
                }
            }
return itemlist;
        }
else
        {
return null;
        }

    }

}

Servlet控制层

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import dao.ItemsDAO;
import entity.Cart;
import entity.Items;

public class CartServlet extends HttpServlet {

private String action;     // action对象有三个动作add show delete
private ItemsDAO idao = new ItemsDAO();

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
        doPost(request, response);
    }

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
if (request.getParameter("action") != null) {
this.action = request.getParameter("action");
if (action.equals("add"))// 添加商品进购物车
            {
if (addToCart(request, response)) {
                    request.getRequestDispatcher("/success.jsp").forward(request, response);
                } else {
                    request.getRequestDispatcher("/failure.jsp").forward(request, response);
                }
            }

if(action.equals("show")){              //显示购物车
                    request.getRequestDispatcher("/cart.jsp").forward(request, response);
             }
if(action.equals("delete")){
if(deleteFromCart(request,response)){
                     request.getRequestDispatcher("/cart.jsp").forward(request, response); 
                 }else{
                     request.getRequestDispatcher("/cart.jsp").forward(request, response); 
                 }
             }
             }
             }



private boolean addToCart(HttpServletRequest request, HttpServletResponse response) {
        String id = request.getParameter("id");
        String number = request.getParameter("num");
        Items item = idao.getItemsById(Integer.parseInt(id));

// 是否第一次给购物车添加商品，需要给session中创建一个新的购物车对象
if (request.getSession().getAttribute("cart") == null) {
            Cart cart = new Cart();
            request.getSession().setAttribute("cart", cart);
        }
        Cart cart = (Cart) request.getSession().getAttribute("cart");
if (cart.addGoodsInCart(item, Integer.parseInt(number))) {
return true;
        } else {
return false;
        }
    }
private boolean deleteFromCart(HttpServletRequest request,HttpServletResponse response){


        String id=request.getParameter("id");
        Cart cart=(Cart)request.getSession().getAttribute("cart");
        Items item=idao.getItemsById(Integer.parseInt(id));
if(cart.removeGoodsFromCart(item)){
return true;
        }else{
return false;
        }
    }

public CartServlet() {
// TODO Auto-generated constructor stub
    }
public void init() throws ServletException {
// Put your code here
    }

}

---

jsp页面

index.jsp

<%@page import="java.util.ArrayList"%>
<%@ page language="java" contentType="text/html; charset=utf-8"
 pageEncoding="utf-8"%>
<%@ page import="entity.Items"%>
<%@ page import="dao.ItemsDAO"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<!--
 <link rel="stylesheet" type="text/css" href="styles.css">
 -->
<style type="text/css">
div{
float:left;
margin: 10px;
}
div dd{
margin:0px;
font-size:10pt;
}
div dd.dd_name
{
color:blue;
}
div dd.dd_city
{
color:#000;
}
</style>
</head>

<body>
<h1 >商品展示</h1>
<hr>

<center>
<table width="750" height="60" cellpadding="0" cellspacing="0" border="0">
<tr>
<td>

<!-- 商品循环开始 -->
<% 
 ItemsDAO itemsDao = new ItemsDAO(); 
 ArrayList<Items> list=itemsDao.getAllItems();
if(list!=null&&list.size()>0)
 {
for(int i=0;i<list.size();i++)
 {
 Items item = list.get(i);
 %>   
<div>
<dl>
<dt>
<a href="details.jsp?id=<%=item.getId()%>"><img src="images/<%=item.getPicture()%>" width="120" height="90" border="1"/></a>
</dt>
<dd class="dd_name"><%=item.getName() %></dd> 
<dd class="dd_city">产地：<%=item.getCity() %>&nbsp;&nbsp;价格￥：<%=item.getPrice() %></dd> 
</dl>
</div>
<!-- 商品循环结束 -->

<%
 }
 } 
 %>
</td>
</tr>
</table>
</center>
</body>
</html>

---

details.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8" %>
<%@ page import="entity.Items"%>
<%@ page import="dao.ItemsDAO"%>
<%
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 'details.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">
 -->
<link href="css/main.css" rel="stylesheet" type="text/css">
<script type="text/javascript" src="js/lhgcore.js"></script>
<script type="text/javascript" src="js/lhgdialog.js"></script>
<script type="text/javascript">
function selflog_show(id)
 { 
var num = document.getElementById("number").value; 
 J.dialog.get({id: 'haoyue_creat',title: '购物成功',width: 600,height:400, link: '<%=path%>/servlet/CartServlet?id='+id+'&num='+num+'&action=add', cover:true});
 }
function add()
 {
var num = parseInt(document.getElementById("number").value);
if(num<100)
 {
 document.getElementById("number").value = ++num;
 }
 }
function sub()
 {
var num = parseInt(document.getElementById("number").value);
if(num>1)
 {
 document.getElementById("number").value = --num;
 }
 }

</script>

<style type="text/css">
hr{

border-color:FF7F00; 
}

div{
float:left;
margin-left: 30px;
margin-right:30px;
margin-top: 5px;
margin-bottom: 5px;

}
div dd{
margin:0px;
font-size:10pt;
}
div dd.dd_name
{
color:blue;
}
div dd.dd_city
{
color:#000;
}
div #cart
{
margin:0px auto;
text-align:right; 
}
span{
padding:0 2px;border:1px #c0c0c0 solid;cursor:pointer;
}
a{
text-decoration: none; 
}
</style>
</head>

<body>
<h1>商品详情</h1>
<a href="index.jsp">首页</a> >> <a href="index.jsp">商品列表</a>
<hr>
<center>
<table width="750" height="60" cellpadding="0" cellspacing="0" border="0">
<tr>
<!-- 商品详情 -->
<% 
 ItemsDAO itemDao = new ItemsDAO();
 Items item = itemDao.getItemsById(Integer.parseInt(request.getParameter("id")));
if(item!=null)
 {
 %>
<td width="70%" valign="top">
<table>
<tr>
<td rowspan="5"><img src="images/<%=item.getPicture()%>" width="200" height="160"/></td>
</tr>
<tr>
<td><B><%=item.getName() %></B></td> 
</tr>
<tr>
<td>产地：<%=item.getCity()%></td>
</tr>
<tr>
<td>价格：<%=item.getPrice() %>￥</td>
</tr>
<tr>
<td>购买数量：<span id="sub" onclick="sub();">-</span><input type="text" id="number" name="number" value="1" size="2"/><span id="add" onclick="add();">+</span></td>
</tr> 
</table>
<div id="cart">
<img src="images/buy_now.png"><a href="javascript:selflog_show(<%=item.getId()%>)"><img src="images/in_cart.png"></a><a href="servlet/CartServlet?action=show"><img src="images/view_cart.jpg"/></a>
</div>
</td>
<% 
 }
 %>
<% 
String list ="";
 //从客户端获得Cookies集合
 Cookie[] cookies = request.getCookies();
 //遍历这个Cookies集合
if(cookies!=null&&cookies.length>0)
 {
for(Cookie c:cookies)
 {
if(c.getName().equals("ListViewCookie"))
 {
 list = c.getValue();
 }
 }
 }

 list+=request.getParameter("id")+"#";
 //如果浏览记录超过1000条，清零.
String[] arr = list.split("#");
if(arr!=null&&arr.length>0)
 {
if(arr.length>=1000)
 {
 list="";
 }
 }
 Cookie cookie = new Cookie("ListViewCookie",list);
response.addCookie(cookie);

 %>
<!-- 浏览过的商品 -->
<td width="30%" bgcolor="#EEE" align="center">
<br>
<b><font color="#FF7F00">您浏览过的商品</font></b><br>
<!-- 循环开始 -->
<% 
 ArrayList<Items> itemlist = itemDao.getViewList(list);
if(itemlist!=null&&itemlist.size()>0 )
 {
 System.out.println("itemlist.size="+itemlist.size());
for(Items i:itemlist)
 {

 %>
<div>
<dl>
<dt>
<a href="details.jsp?id=<%=i.getId()%>"><img src="images/<%=i.getPicture() %>" width="120" height="90" border="1"/></a>
</dt>
<dd class="dd_name"><%=i.getName() %></dd> 
<dd class="dd_city">产地:<%=i.getCity() %>&nbsp;&nbsp;价格:<%=i.getPrice() %> ￥ </dd> 
</dl>
</div>
<% 
 }
 }
 %>
<!-- 循环结束 -->
</td>
</tr>
</table>
</center>
</body>
</html>

---

success.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
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 'success.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="style.css">
 -->

</head>

<body>
<center>
<img src="images/add_cart_success.jpg"/>
<hr>
<% 
String id = request.getParameter("id");
String num = request.getParameter("num");
 %>
             您成功购买了<%=num%>件商品编号为<%=id%>的商品&nbsp;&nbsp;&nbsp;&nbsp;
<br>
<br>
<br>

</center>
</body>
</html>

---

failure.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
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 'success.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>
<center>
<img src="images/add_cart_failure.jpg"/>
<hr>

<br>
<br>
<br>

</center>
</body>
</html>

---

cart.jsp

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%@ page import="entity.Cart" %>
<%@ page import="entity.Items" %>
<%
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 'cart.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">
 -->
<link type="text/css" rel="stylesheet" href="css/style1.css" />
<script language="javascript">
function delcfm(){
if(!comfirm("确认要删除？")){
 window.event.returnValue=false;
 }
 }
</script>
</head>

<body>
<h1>我的购物车</h1>
<a href="index.jsp">首页</a> >> <a href="index.jsp">商品列表</a>
<hr> 
<div id="shopping">
<form action="" method="">       
<table>
<tr>
<th>商品名称</th>
<th>商品单价</th>
<th>商品价格</th>
<th>购买数量</th>
<th>操作</th>
</tr>
<% 
 //首先判断session中是否有购物车对象
if(request.getSession().getAttribute("cart")!=null)
 {
 %>
<!-- 循环的开始 -->
<% 
 Cart cart=(Cart)request.getSession().getAttribute("cart");
 HashMap<Items,Integer> goods=cart.getGoods();
Set<Items> items=goods.keySet();
 Iterator<Items> it=items.iterator();

while(it.hasNext()){
 Items i=it.next();
 %> 
<tr name="products" id="product_id_1">
<td class="thumb"><img src="images/<%=i.getPicture()%>" /><a href=""><%=i.getName()%></a></td>
<td class="number"><%=i.getPrice() %></td>
<td class="price" id="price_id_1">
<span><%=i.getPrice()*goods.get(i) %></span>
<input type="hidden" value="" />
</td>
<td class="number">
<%=goods.get(i)%>                   
</td>                        
<td class="delete">
<a href="servlet/CartServlet?action=delete&id=<%=i.getId()%>" onclick="delcfm();">删除</a>   <!-- onclick 调用js删除方法 -->                           
</td>
</tr>
<% 
 }
 %>
<!--循环的结束-->

</table>
<div class="total"><span id="total">总计：<%=cart.getTotalPrice() %>￥</span></div>
<% 
 }
 %>
<div class="button"><input type="submit" value="" /></div>
</form>
</div>
</body>
</html>

---

---

WEB.xml
servlet类一定不要忘记配置xml文档！！！切记！！

<servlet>
<servlet-name>CartServlet</servlet-name>
<servlet-class>servlet.CartServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>CartServlet</servlet-name>
<url-pattern>/servlet/CartServlet</url-pattern>
</servlet-mapping>

参照慕课网课程项目实例