使用Cookie防刷新页面计数功能(纯源码+注解)

原创

小明Java问道之路 2022-06-27 10:44:40 博主文章分类：项目实战 ©著作权

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(1)功能描述（登录、复选框购书、退出）
(2)记录是第几位选书者（防止刷新的计数器，并且相同用户名下次登录进入选书页面，不进行累加，并显示上次登录的时间）

每行代码基本都有注释：

<%@ 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>登录页</title>
</head>
<body>
<form action="LoginServlet" method="get" id="myform">
            <label>请登录</label>
            <br /><br />
            <label for="name">账户名:</label>
            <input type="text" name="name"/>
            <br />
            <br />
            <label for="password">密　码:</label>
            <input type="password" name="password"/>(初始密码：123)
            <br />
            <br />
            <input type="submit" value="登 陆"  class="input_submit"/>
        </form>
</body>
</html>

LoginServlet

package com.servlet;

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;

public class LoginServlet extends HttpServlet {
  static int visitCount = 1;

  protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    response.setCharacterEncoding("UTF-8"); // 解决中文乱码 （如果删掉用不了中文）
    response.setHeader("content-type", "text/html;charset=UTF-8");
    // 获取用户名密码
    String name = request.getParameter("name");
    String password = request.getParameter("password");
    
    System.out.println(name + password);
    if (name != "" && name != null && password.equals("123")) { // 校验用户名非空 以及 指定的密码 123
      // 创建cookie
      Cookie c1 = new Cookie("username", name);
      // 服务器将cookie发送给客户端，方便下一次请求时携带
      response.addCookie(c1);
      response.setHeader("username", name);

      System.out.println("登录成功");
      request.getSession().setAttribute("username", name); // 设置Session
      request.getRequestDispatcher("BookServlet").forward(request, response); // 跳转到BookServlet
    } else {
      System.out.println("登录失败");
      request.getRequestDispatcher("login.jsp").forward(request, response); // 跳转到login.jsp
    }
  }

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

}

BookServlet

package com.servlet;

import java.io.IOException;
import java.util.Date;

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

public class BookServlet extends HttpServlet {
  static int visitCount = 0;

  protected void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    response.setCharacterEncoding("UTF-8");
    request.setCharacterEncoding("UTF-8");
    response.setHeader("content-type", "text/html;charset=UTF-8");
    String username = (String) request.getSession().getAttribute("username"); // 设置Session  - 保存用户

    // 加入防刷机制
    boolean justVisit = false; // 是否在指定的时间内访问过
    Cookie[] cookies = request.getCookies(); // 获取Cookie数组
    if (null != cookies) {
      for (Cookie cookie : cookies) {
        if (username.equals(cookie.getName())) { // 如果已经登录了
          justVisit = true; break;
        }
      }
    }
    if (!justVisit) { // 如果最近没有访问过
      Cookie coo = new Cookie(username, "value");
      coo.setMaxAge(5 * 60); // 设置了最大保存时间
      response.addCookie(coo);
      visitCount = visitCount + 1; // 访问量+1
    }

    // 获取session创建时间
    Date createTime = new Date(request.getSession().getCreationTime());

    // 获取最后访问页面的时间
    Date lastAccessTime = new Date(request.getSession().getLastAccessedTime());

    System.out.println("访问量" + visitCount);
    request.getSession().setAttribute("visitCount", visitCount); // 保存人数
    request.getSession().setAttribute("lastAccessTime", lastAccessTime); // 最后登录时间 （页面没加）
    request.getSession().setAttribute("createTime", createTime); // 上次登录时间

    // 获取图书信息
    String category1 = request.getParameter("category1");
    String category2 = request.getParameter("category2");
    String category3 = request.getParameter("category3");
    String category4 = request.getParameter("category4");
    String name = (String) request.getSession().getAttribute("username"); // 获取
    System.out.println("用户名 ：" + name + "   选择的图书：" + category1 + category2 + category3 + category4);

    request.getRequestDispatcher("book.jsp").forward(request, response); // 跳转页面
  }

  protected void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doGet(request, response);
  }

}

Book.jsp

<%@ 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>

<p align="center">您是第<b><font color="red">${visitCount}</font></b>位客人。</p>
<table  border="1" align="center">
<tr>
   <td>上次登录时间</td>
   <td>${createTime}</td>
</tr> 
<tr>
   <td>Number of visits</td>
   <td>${visitCount}</td>
</tr> 
</table>

<form action="BookServlet" method="post" id="myform">
   <% String username = (String)request.getSession().getAttribute("username"); // 获取Session  %>
   <%=username %> - 请选择你想看的书
   
    <p><input type="checkbox" name="category1" value="JavaWeb核心技术" />JavaWeb核心技术 </p>   
    <p><input type="checkbox" name="category2" value="Java从入门到到精通" />Java从入门到到精通</p>
    <p><input type="checkbox" name="category3" value="数据结构与算法分析" />数据结构与算法分析</p>    
    <p><input type="checkbox" name="category4" value="设计模式之美" />设计模式之美</p>     
    <p><input type="submit" value="选择"/></p>
    <a href="DeleteServlet">退出</a>
</form>

</body>
</html>

//加入防刷机制
     boolean justVisit = false; //是否在指定的时间内访问过
     Cookie[] cookies = request.getCookies();
     if (null != cookies) {
         for (int i = cookies.length - 1; i >= 0; i--) {
             if (("Bwl_App_" + userName).equals(cookies[i].getName())) {
                 justVisit = true; break;  }
         }
     }  if (!justVisit) { //如果最近没有访问过
         Cookie coo = new Cookie("Bwl_App_" + userName, "value");
         response.addCookie(coo);     }