J2EE實現jsp運用Servlet Cookie達到記住賬號密碼功能！

可以先看看別的大佬寫的瞭解下cookie，具體我也不知道怎麼講哈哈哈哈或或或！

然後自己寫了個記住賬號密碼功能，附帶查看cookie的值，刪除cookie的功能！

首先，在index.jsp中寫好登錄界面，並添加獲取cookie中賬號和密碼信息並放進input中。以下是代碼：

<%--
  Created by IntelliJ IDEA.
  User: HSW
  Date: 2018/4/20
  Time: 11:09
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%
    Cookie[] cookies = request.getCookies();
    String admin = "";
    String password = "";
    if(cookies != null)
        for(Cookie cookie : cookies){
            if(cookie.getName().equals("admin"))
                 admin = cookie.getValue();
            else if(cookie.getName().equals("pwd"))
                password = cookie.getValue();
        }
%>
<html>
  <head>
    <title>Cookie Login</title>
    <style>
      div{
        width: 800px;
        height: 800px;
        margin: 200px auto;
      }
      h1{
          width: 400px;
          height: auto;
          margin: 0 auto;
      }
        table{
            width: 400px;
            height: auto;
            margin: 0 auto;
        }
    </style>
  </head>
  <body>
    <form action="${pageContext.request.contextPath}/setcookie" method="post">
      <div>
        <h1>登錄</h1>
        <table>
          <tr><td><label for="admin">用戶名：</label></td>
            <td><input type="text" id="admin" placeholder="請輸入你的用戶名" name="admin" value="<%=admin%>"></td></tr>
          <tr><td><label for="pwd">密碼：</label></td>
            <td><input type="password" id="pwd" name="pwd" value="<%=password %>"></td></tr>
          <tr><td><input type="submit" value="登錄"></td><td><input type="reset" value="重置"></td></tr>
        </table>
      </div>
    </form>
  </body>
</html>

將上面java代碼字符串信息放進input框裏面的方法就是像上面的這句一樣：

value="<%=password %>">

每次訪問這個頁面時就先執行上面的java程序，第一次時沒有賬號信息，getCookies返回空，所以就不會自動填補input！

然後新建一個Servlet相當於下面的A服務器，將登錄信息放進Cookie！

代碼如下：

package cn.jxufe;

import javax.servlet.http.Cookie;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class CookieSer extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        response.setContentType("text/html; charset=utf-8");
        String admin = request.getParameter("admin");
        String password = request.getParameter("pwd");
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd  hh:mm:ss");
        String datestr = format.format(new Date());
        Cookie cookie = new Cookie("admin", admin);
        Cookie cookie2 = new Cookie("pwd", password);
        Cookie cookie3 = new Cookie("date", URLEncoder.encode(datestr,"utf-8"));
        response.addCookie(cookie);
        response.addCookie(cookie2);
        response.addCookie(cookie3);
        PrintWriter out = response.getWriter();

        out.write("<html>");
        out.write("<head>");
        out.write("<title>WebCookie</title>");
        out.write("</head>");
        out.write("<body>");
        out.write("賬號密碼已被添加進cookie");
        out.write("<a href=\"/look\">查看登錄信息</a>");
        out.write("</body>");
        out.write("</html>");
    }

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

效果：

可以看到將賬號、密碼、最近一次登錄時間都寫進了cookie。

這時返回登錄界面刷新下看看：

賬號密碼都被保存！

然後在上面的Servlet加了一個<a>跳轉至另一個查看cookie信息的Servlet，名爲LookCookieContent（url-pattern是/look），代碼：

package cn.jxufe;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;

public class LookCookieContent extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        Cookie[] cookies = request.getCookies();
        String admin = "暫無該項信息";
        String password = "暫無該項信息";
        String date = "暫無該項信息";
        if(cookies != null)
            for(Cookie cookie : cookies){
                if(cookie.getName().equals("admin"))
                    admin = cookie.getValue();
                else if(cookie.getName().equals("pwd"))
                    password = cookie.getValue();
                else if(cookie.getName().equals("date"))
                    date = URLDecoder.decode(cookie.getValue(), "utf-8");
        }
        PrintWriter out = response.getWriter();

        out.write("<html>\n" +
                "<head>\n" +
                "    <title>Cookie Login</title>\n" +
                "    <style>\n" +
                "        div{\n" +
                "            width: 800px;\n" +
                "            height: 800px;\n" +
                "            margin: 200px auto;\n" +
                "        }\n" +
                "        h1{\n" +
                "            width: 400px;\n" +
                "            height: auto;\n" +
                "            margin: 0 auto;\n" +
                "        }\n" +
                "        table{\n" +
                "            width: 400px;\n" +
                "            height: auto;\n" +
                "            margin: 0 auto;\n" +
                "        }\n" +
                "    </style>\n" +
                "</head>\n" +
                "<body>\n" +
                "    <div>\n" +
                "        <table> \n" +
                "          <tr><td>賬號：</td><td>" + admin +"</td></tr> \n" +
                "          <tr><td>密碼：</td><td>" + password +"</td></tr>\n" +
                "          <tr><td>上次登陸時間：</td><td>" + date + "</td></tr>\n" +
                "          <tr><td colspan=\"2\"><a href=\"\">刪除cookie</a></td></tr>\n" +
                "      </table>\n" +
                "    </div>\n" +
                "</body>\n" +
                "</html>");
    }

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

單相思的情場失意，原本糟糕的心情隨着一晚上的代碼時光慢慢變好，現在依舊沒有絲毫睡意，這難道就是學習使我快樂嗎？

我還是和我現任女友好好處吧曬出來一起養養眼

emm~繼續講，接下來就是刪除cookie了，很簡單就是設置maxAge爲0就行了！

這個是自己寫的無法正常刪除cookie的代碼（too young啊）：

package cn.jxufe;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "DeleteCookieServlet")
public class DeleteCookieServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie[] cookies = request.getCookies();
        if(cookies != null)
            for(Cookie cookie : cookies)
                cookie.setMaxAge(0);
        RequestDispatcher dispatcher = request.getRequestDispatcher("index.jsp");
        dispatcher.forward(request, response);
    }

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

關於cookie的壽命信息：

在代碼中，我們用Cookie.setMaxAge()設置Cookie的生命週期。在這個方法中如果沒有參數的話，默認參數就是-1，表示是會話時期cookie，當結束會話或關閉瀏覽器就會刪除。當設置了一個正值，即生命週期是這個正值的秒數，cookie將會保存至硬盤。而像上面那樣直接設置爲0，即直接刪除該Cookie！

運行代碼發現無法正常刪除，查找原因發現是因爲沒有執行response.addCookie()將原來的cookie覆蓋！

加上試試。

點擊刪除cookie，返回登錄界面時還是有的，因爲網頁有緩存，刷新下就沒有了！