JAVAEE model1模型实现商品浏览记录（去除重复的浏览记录）（一）

在javaee中Model1模型是以jsp页面为中心的，jsp既要对浏览器的request做出逻辑处理（使用javabean），访问数据库也要显示出相关的页面。
在model1模型中，没有servlet。
Model1结果图如下：

Model1的可维护性  可扩展性都是较差的  只适合小项目。

首先运行结果

goods.jsp

<%@page import="entity.Items"%>
<%@page import="dao.ItemsDao"%>
<%@ page language="java" import="java.util.*" pageEncoding="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 '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">
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>
  <center>
    <h1>商品展示</h1>
    <hr>
    <table width="800" height="60" cellpadding="0" cellspacing="0"
      border="0">
      <tr>
        <td>
          <%
            ItemsDao dao = new ItemsDao();
            ArrayList<Items> list = new ArrayList<Items>();
            //从dao中获取所有的商品 并保存到list集合中
            list = dao.getAllItems();
            if (list != null && list.size() > 0) {
              //循环遍历集合 并显示
              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()%> 价格:￥
                <%=item.getPrice()%></dd>
            </dl>
          </div> <%
  }
  }
 %>
        </td> 

      </tr>
    </table>
  </center>
</body>
</html>

在代码中 表示商品的图片

<span style="white-space:pre">               </span>

<a href="details.jsp?id=<%=item.getId()%>">

<img src="images/<%=item.getPicture()%>" width="120" height="90"  border="1" /> 

</a>

通过点击商品的图片  把当前商品的id传值给details页面
details.jsp通过商品的id来显示详细商品  ，而浏览记录由cookies维护

<%@page import="org.apache.taglibs.standard.tag.common.xml.ForEachTag"%>
<%@page import="entity.Items"%>
<%@page import="dao.ItemsDao"%>
<%@ page language="java" import="java.util.*" pageEncoding="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 '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">
<style type="text/css">
#historyview {
  border: 1;
  background: #EAEAEE;
} 

#historyview td {
  font-size: 10px;
}
</style>
</head> 

<body>
  <center>
    <h1>商品详情</h1>
    <hr>
    <table width="750" border="0" cellpadding="0" cellspacing="0">
      <tr>
        <td width="70%">
          <center>
            <table border="0">
              <%
                ItemsDao dao = new ItemsDao();
                //根据request传来的商品id 向dao中获得相对应的商品对象
                Items item = dao.getItemById(Integer.parseInt(request
                    .getParameter("id")));
                if (item != null) {
              %>
              <tr>
                <td rowspan="5"><img src="images/<%=item.getPicture()%>"
                  width="200" height="150"></td>
              </tr>
              <tr>
                <td><b><%=item.getName()%></b>
                </td>
              </tr>
              <tr>
                <td id="cityname">产地：<%=item.getCity()%></td>
              </tr>
              <tr>
                <td id="pricename">价格：<%=item.getPrice()%> ￥</td>
              </tr>
              <tr>
                <td id="pricename">价格：<%=item.getPrice()%> ￥</td>
              </tr>
              <%
                }
                //将该商品加入cookies
                Cookie[] cookies = request.getCookies();
                String historyStr = "";
                for (Cookie c : cookies) {
                  if (c.getName().equals("history")) {
                    historyStr = c.getValue();
                  }
                }
                historyStr += item.getId() + ",";
                Cookie c = new Cookie("history", historyStr);
                //重新设置cookies
                response.addCookie(c);
              %>
            </table>
          </center></td> 

        <td width="30%" valign="top" id="historyview">
          <center>
            <table>
              <tr>
                <td><b>你浏览过的商品</b></td>
              </tr>
              <%
                //根据cookie 从dao获取最后浏览的三次记录 并保存到list集合
                ArrayList<Items> historyItems = dao.getHistoryView(historyStr);
                if (historyItems != null && historyItems.size() > 0) {
                  //遍历集合
                  for (Items historyItem : historyItems) {
              %>
              <tr>
                <td><a href="details.jsp?id=<%=historyItem.getId()%>"><img
                    src="images/<%=historyItem.getPicture()%>" width="100"
                    height="80" border="1"> </a></td>
              </tr>
              <tr>
                <td><b><%=historyItem.getName()%></b>
                </td>
              </tr>
              <tr>
                <td>产地：<%=historyItem.getCity()%></td>
              </tr>
              <%
                }
                }
              %>
            </table>
          </center>
        </td>
      </tr>
    </table> 

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

dao层  负责商品在数据库中的查询操作

package dao; 

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import util.DBHelper;
import entity.Items; 

//商品的业务逻辑类
public class ItemsDao {
  // 获得所有商品信息
  public ArrayList<Items> getAllItems() {
    // 商品集合
    ArrayList<Items> list = new ArrayList<Items>();
    Connection conn = null;
    PreparedStatement ps = null;
    ResultSet rs = null; 

    try {
      conn = DBHelper.getConnection();
      String sql = "select * from items";// sql 语句
      ps = conn.prepareStatement(sql);
      rs = ps.executeQuery();
      // 将查询的结果依次加入集合
      while (rs.next()) {
        Items item = new Items();
        item.setId(rs.getInt("id"));
        item.setName(rs.getString("name"));
        item.setCity(rs.getString("city"));
        item.setPrice(rs.getDouble("price"));
        item.setPicture(rs.getString("picture"));
        item.setNumber(rs.getInt("number"));
        list.add(item);
      }
    } catch (SQLException e) { 

      e.printStackTrace();
    } finally {
      // 关闭资源
      if (rs != null) {
        try {
          rs.close();
        } catch (SQLException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      }
      if (ps != null) {
        try {
          ps.close();
        } catch (SQLException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      } 

    }
    return list;
  } 

  // 根据商品编号获取商品资料 

  public Items getItemById(int id) {
    Items item = new Items();
    Connection con = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    String sql = "select * from items where id = ?";
    try {
      con = DBHelper.getConnection();
      ps = con.prepareStatement(sql);
      ps.setInt(1, id);
      rs = ps.executeQuery();
      // 如果找到该id 为item对象初始化
      if (rs.next()) {
        item.setId(rs.getInt("id"));
        item.setName(rs.getString("name"));
        item.setCity(rs.getString("city"));
        item.setPrice(rs.getDouble("price"));
        item.setPicture(rs.getString("picture"));
        item.setNumber(rs.getInt("number"));
      } 

    } catch (SQLException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      // 关闭资源
      if (rs != null) {
        try {
          rs.close();
        } catch (SQLException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      }
      if (ps != null) {
        try {
          ps.close();
        } catch (SQLException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
        }
      }
    }
    return item;
  } 

  // 根据cookie 获得浏览的最后三个商品
  public ArrayList<Items> getHistoryView(String cookie) {
    ArrayList<Items> list = new ArrayList<Items>();
    String ids[] = cookie.split(",");
    int counts = 3;// 浏览的最后三条记录
    if (ids != null && ids.length > 0) {
      for (int i = ids.length - 1; i >= 0 && i > ids.length - counts - 1; i--) {
        Items item = getItemById(Integer.parseInt(ids[i]));
        /*
         * 首先判断集合中是否存在当前物品 如果存在 counts+1 多读取一次（保证list集合中有3个对象） 不添加此物品
         */
        if (list.contains(item)) {
          counts++;
          continue;
        }
        list.add(item);
      }
    }
    return list;
  }
}

商品的实体类 Items

package entity; 

public class Items {
  private int id;
  private String name;
  private String city;
  private double price;
  private int number;
  private String 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 double getPrice() {
    return price;
  } 

  public void setPrice(double 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) {
    if(this==obj)
    {
      return true;
    }
    else
    {
      if(obj instanceof Items)
      {
        Items item=(Items) obj;
        if(this.getId()==item.getId()&&this.getName().equals(item.getName()))
        {
          return true;
        }
      }
    }
    return false;
  }
}

在这里  重写了hasCode和equals方法  来修改比较方式（所有的item都是一个新的对象 即使两个商品的内容全部一样也不会相等  。所以要修改比较方式）
因为对于浏览记录而言  我们不能通过刷新当前商品  浏览记录全部都是该商品 我们只要保证该商品在浏览记录中 只有一个即可
所以在dao层中的getHistoryView方法有这句代码

<span style="white-space:pre">       </span>if (list.contains(item)) {
          counts++;
          continue;
        } 

然后是工具类
DBHelpher 单例模式获得connection对象

package util; 

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

public class DBHelper {
  private static final String driver = "com.mysql.jdbc.Driver";
  private static final String url = "jdbc:mysql://localhost:3306/shopping?useUnicode=true&charcterEncoding=UTF-8";
  private static final String username = "root";
  private static final String password = "123";
  private static Connection con = null;
  // 静态块代码负责加载驱动
  static {
    try {
      Class.forName(driver);
    } catch (ClassNotFoundException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  } 

  public static Connection getConnection() { 

    if (con == null) {
      try {
        con = DriverManager.getConnection(url, username, password);
      } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      }
    }
    return con;
  }
} 

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。