JSP读取数据库、JDBC、Cookie存取

一个JSP读取数据库和Cookie存取存取的实例

项目运行结果如下

JDBC DbHelper.java

package util;

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

public class DbHelper {

    // 数据库驱动
    private static final String driver = "com.mysql.jdbc.Driver";
    // 数据库
    private static final String url = "jdbc:mysql://localhost:3306/db_test";
    // 数据库用户名和密码
    private static final String username = "root";
    private static final String password = "root";

    private static Connection connection = null;

    // 静态代码块，负责加载驱动
    static {
        try {
            Class.forName(driver);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 单例模式返回数据库连接对象
    public static Connection getConnection() throws Exception {

        if (connection == null) {
            connection = DriverManager.getConnection(url, username, password);
            return connection;
        }
        return connection;
    }

    // 主函数测试本类方法
    public static void main(String[] args) {
        System.out.println("主函数启动");
        try {
            Connection conn = DbHelper.getConnection();
            if (conn != null) {
                System.out.println("数据库连接正常");
            } else {
                System.out.println("数据库连接异常");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

实体类 Shopping.java

package entity;

public class Shopping {
    private int id;
    // 名称、产地、价格、库存、图片
    private String name;
    private String city;
    private int 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 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;
    }
}

逻辑层 ShoppingDAO.java

package dao;

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

import entity.Shopping;
import util.DbHelper;

// 业务逻辑类
public class ShoppingDAO {

    // 获取所有商品信息
    public ArrayList getAllShopping() {
        Connection conn = null;
        PreparedStatement stat = null;
        ResultSet rSet = null;
        // 商品集合
        ArrayList list = new ArrayList();

        try {
            conn = DbHelper.getConnection();
            String sql = "SELECT * FROM shopping;";
            stat = conn.prepareStatement(sql);
            rSet = stat.executeQuery();
            while (rSet.next()) {
                Shopping sh = new Shopping();
                sh.setId(rSet.getInt("id"));
                sh.setName(rSet.getString("name"));
                sh.setCity(rSet.getString("city"));
                sh.setNumber(rSet.getInt("number"));
                sh.setPrice(rSet.getInt("price"));
                sh.setPicture(rSet.getString("picture"));
                list.add(sh);
            }
            return list;

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

    // 根据商品Id获得商品资料
    public Shopping getShoppingById(int id) {
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet rSet = null;

        try {
            connection = DbHelper.getConnection();
            String sql = "SELECT * FROM shopping WHERE id = ?;";
            statement = connection.prepareStatement(sql);
            statement.setInt(1, id);
            rSet = statement.executeQuery();
            if (rSet.next()) {
                Shopping item = new Shopping();
                item.setId(rSet.getInt("id"));
                item.setName(rSet.getString("name"));
                item.setCity(rSet.getString("city"));
                item.setNumber(rSet.getInt("number"));
                item.setPrice(rSet.getInt("price"));
                item.setPicture(rSet.getString("picture"));
                return item;
            }
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            // 释放数据集对象
            if (rSet != null) {
                try {
                    rSet.close();
                    rSet = null;
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
            // 释放语句对象
            if (statement != null) {
                try {
                    statement.close();
                    statement = null;
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        }

        return null;
    }

    // 获取最近浏览的前5条商品信息
    public ArrayList getViewList(String list) {

        ArrayList itemlist = new ArrayList();
        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("当前缓存的个数：arr.length=" + arr.length);
            // 如果商品记录大于等于5条，则返回最新的5条数据，否则返回所有的数据
            if (arr.length >= 5) {
                for (int i = arr.length - 1; i >= arr.length - iCount; i--) {
                    itemlist.add(getShoppingById(Integer.parseInt(arr[i])));
                }
            } else {
                for (int i = arr.length - 1; i >= 0; i--) {
                    itemlist.add(getShoppingById(Integer.parseInt(arr[i])));
                }
            }
            return itemlist;
        } else {
            return null;
        }
    }

}

index.jsp

<body>
    <h2>商品展示h2>
    <br>

    <div class="contentBox">
        <%
            ShoppingDAO dao = new ShoppingDAO();
            ArrayList list = dao.getAllShopping();
            if (list != null && list.size() > 0) {
                for (int i = 0; i < list.size(); i++) {
                    Shopping sh = list.get(i);
        %>
        <div class="item">
            
            <a href="detail.jsp?id=<%=sh.getId()%>"> <img alt=""
                src="images/<%=sh.getPicture()%>" />a>
            <div class="price">
                ¥<%=sh.getPrice()%>div>
            <div class="name"><%=sh.getName()%>div>
            <div class="city">
                产地:<%=sh.getCity()%>div>
        div>
        <%
            }
            }
        %>
    div>
body>

detail.jsp

<body>

    <h1>商品详情h1>
    <br>

    <%
        ShoppingDAO dao = new ShoppingDAO();
        Shopping sh = dao.getShoppingById(Integer.parseInt(request.getParameter("id")));
        if (sh != null) {
    %>
    <div class="content">
        <img alt="" src="images/<%=sh.getPicture()%>">
        <div class="rightBox">
            <div class="name"><%=sh.getName()%>div>
            <div class="price">
                ¥
                <%=sh.getPrice()%>div>
            <div class="city">
                产地：<%=sh.getCity()%>div>
            <div class="sales">
                销量：<%=sh.getNumber()%>件
            div>
        div>
    div>
    <%
        }
    %>

    
    <div class="history">
        浏览历史记录

        <%
        String list = "";
        /* 从客户端读取Cookies集合 */
        Cookie[] cookies = request.getCookies();
        if (cookies != null && cookies.length > 0) {
            /* 遍历Cookies集合 */
            for (Cookie c : cookies) {
                if (c.getName().equals("COOKIE")) {
                    /* 获取Cookie的值 */
                    list = c.getValue();
                }
            }
        }

        /* 用#分割各个id */
        list += request.getParameter("id") + "#";
        // 如果浏览记录超过100条，清零
        String[] arr = list.split("#");
        if (arr != null && arr.length > 0) {
            if (arr.length >= 100) {
                list = "";
            }
        }
        /* 创建Cookie对象 */
        Cookie cookie = new Cookie("COOKIE", list);
        System.out.println("当前缓存到Cookie的值(商品id)----" + list);
        /* 写入Cookie对象 */
        response.addCookie(cookie);
    %>

        
        <%
            ArrayList shopplist = dao.getViewList(list);
            if (shopplist != null && shopplist.size() > 0) {
                for (Shopping shh : shopplist) {
        %>

        <div class="historyItem">
            <a href="detail.jsp?id=<%=shh.getId()%>"><img alt=""
                src="images/<%=shh.getPicture()%>"> a>
            <div class="name"><%=shh.getName()%>div>
            <div class="city">
                产地：<%=shh.getCity()%>div>
            <div class="price">
                ¥<%=shh.getPrice()%>div>
        div>

        <%
            }
            }
        %>

    div>

body>

需要注意的点：
在项目中需要导入MySQL JAR包，否则JDBC 报错
在Tomcat中导入MySQL JAR包，否则JSP 页面报错
JSP 需要 import 导入实体类和逻辑层

完整源代码地址