显示商品浏览记录与删除浏览记录

系统管理员 2022-07-14 07:17 189阅读 0赞

给商品一个列表，并且每一件商品设置一个编号，用户点击每个商品时都会向servlet提交一个请求，servlet得知用户点击了哪件商品，并将商品编号保存在cookie中，用框图表示：

![这里写图片描述][20161129205156433]

可以通过JSP与Servlet的结合来实现这一功能，利用JSP作为View，利用Servlet作为Control。

首先我们需要实现一个商品列表：

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <!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=UTF-8">
    <title>Insert title here</title>
    </head>
    <body>
    
    <h1>商品列表</h1>
    
    <a href="/history/producthistory?id=1">冰箱</a><br/>
    <a href="/history/producthistory?id=2">洗衣机</a><br/>
    <a href="/history/producthistory?id=3">笔记本电脑</a><br/>
    <a href="/history/producthistory?id=4">手机</a><br/>
    <a href="/history/producthistory?id=5">空调</a><br/>
    <a href="/history/producthistory?id=6">热水器</a><br/>
    <a href="/history/producthistory?id=7">微波炉</a><br/>
    <a href="/history/producthistory?id=8">电风扇</a><br/>
    
    <h1>商品浏览记录</h1>
    <%
        Cookie[] cookies = request.getCookies();
        if(cookies == null){
            out.println("无浏览记录");
        }else{
            //遍历cookie，找到对应的history
            for(Cookie c:cookies){
                if(c.getName().equals("history")){
                    String id = c.getValue();
                    String[] arr = { "冰箱", "洗衣机", "笔记本电脑", "手机", "空调", "热水器", "微波炉", "电风扇" };
                    out.println(arr[Integer.parseInt(id)-1]);
                }
            }
        }
    
    %>
    </body>
    </html>

Servlet程序，使用cookie不要忘记import对应包（import javax.servlet.http.Cookie;）

package cn.megustas.servlet.cookie.demo1;
    
    import java.io.IOException;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.Cookie;
    
    /**
     * 浏览商品，将商品浏览记录添加到cookie
     */
    
    public class ProductHistoryServlet extends HttpServlet {
        
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //1获得商品编号
            String id = request.getParameter("id");
            //2将商品编号存入cookie
            Cookie cookie = new Cookie("history",id);
            cookie.setMaxAge(60*60);
            cookie.setPath("/history");
            //3写回cookie
            response.addCookie(cookie);
            //提示用户浏览的是哪件商品
            //如果是真正的系统开发，商品信息应该存储在数据库中
            String[] arr = { "冰箱", "洗衣机", "笔记本电脑", "手机", "空调", "热水器", "微波炉", "电风扇" };
            response.setContentType("text/html;charset=utf8");
            response.getWriter().println("用户正在浏览商品：" + arr[Integer.parseInt(id) - 1]);
    
        }
    
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // TODO Auto-generated method stub
            doGet(request, response);
        }
    
    }

对Servlet程序进行配置

<?xml version="1.0" encoding="UTF-8"?>
    <web-app version="2.5" 
        xmlns="http://java.sun.com/xml/ns/javaee" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
        http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    
    <servlet>
        <servlet-name>ProductHistory</servlet-name>
        <servlet-class>cn.megustas.servlet.cookie.demo1.ProductHistoryServlet</servlet-class>
    </servlet>  
    
    <servlet-mapping>
        <servlet-name>ProductHistory</servlet-name>
        <url-pattern>/producthistory</url-pattern>
    </servlet-mapping>
    
    </web-app>

改进：对于一些经常使用的操作，我们可以将其抽取出来，我们可以定义一个类CookieUtils：

package cn.megustas.utils;
    import javax.servlet.http.Cookie;
    
    /**
     * 经常读取Cookie，每次读取需要执行for循环，将读取cookie操作抽取出来
     * 
     * @author megustas
     * 
     */
    public class CookieUtils {
        
        /**
         * 在Cookie数组中 查找指定name cookie
         * 
         * @param cookies
         * @param name
         * @return
         */
        public static Cookie findCookie(Cookie[] cookies, String name) {
            if (cookies == null) {
       // 没有cookie
                return null;
            } else {
                for (Cookie cookie : cookies) {
                    if (cookie.getName().equals(name)) {
                        return cookie;
                    }
                }
                return null;
            }
        }
    }

![这里写图片描述][20161201181856850]

**删除浏览记录**

package cn.megustas.servlet.cookie.demo1;
    import java.io.IOException;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /**
     * 清除 history的cookie信息
     * 
     * @author megustas
     * 
     */
    public class CleanHistoryServlet extends HttpServlet {
        
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            Cookie cookie = new Cookie("history", "");
    
            // 设置MaxAge 为0，即删除了cookie
            cookie.setMaxAge(0);
    
            // path一致
            cookie.setPath("/history");
    
            response.addCookie(cookie);
    
            // 跳转到商品列表页面 ：转发或重定向，从性能上说，转发好于重定向
            //request.getRequestDispatcher("/cookie/demo/product.jsp").forward(request,response);
            //重定向
            response.sendRedirect("/history/cookie/demo/product.jsp");
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }
    
    }

同理，在JSP中的操作也可以通过import我们所定义的包来进行简化，其完整实现代码可以到[https://coding.net/u/TwistFate/p/ShoppingHistory/git/tree/master/history][https_coding.net_u_TwistFate_p_ShoppingHistory_git_tree_master_history]进行下载。

[20161129205156433]: /images/20220714/372e589551154273ad0a2789941b3d4f.png
[20161201181856850]: /images/20220714/4050da5600e64bfe86980b7227cd35b1.png
[https_coding.net_u_TwistFate_p_ShoppingHistory_git_tree_master_history]: https://coding.net/u/TwistFate/p/ShoppingHistory/git/tree/master/history