Cookie案例：简单登录界面中的应用

ServletDemo1.java

 package ztq.servlet.study;
import java.io.IOException;

 import java.io.PrintWriter;
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 ServletDemo1 extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         //设置服务器端以UTF-8编码进行输出

         response.setCharacterEncoding("UTF-8");

         //设置浏览器以UTF-8编码进行接收，解决中文乱码问题

         response.setContentType("text/html;charset = UTF-8");

         PrintWriter out = response.getWriter();
//获取cookie

         String username = "";

         String check = "";

         Cookie[] cookies = request.getCookies();

         for(int i = 0; cookies != null && i < cookies.length; i++){

             Cookie c = cookies[i];

             if("username".equals(c.getName())){

                 username = c.getValue();

                 check = "checked = 'checked'";

                 break;

             }

         }
//登录页面

         out.write("<form action = '" + request.getContextPath() + "/servlet/ServletDemo2' method = 'post'>");

         out.write("用户名：<input type = 'text' name = 'username' value = '" + username + "'><br />");

         out.write("密码：<input type = 'password' name = 'password' value = ''><br />");

         out.write("记住用户名：<input type = 'checkbox' name = 'remember'" + check + "'><br />");

         out.write("<input type = 'submit' name = 'submit' value = '登录'><br />");

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         doGet(request, response);

     }

 }

ServletDemo2.java

package ztq.servlet.study;
import java.io.IOException;

import java.io.PrintWriter;
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 ServletDemo2 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String username = request.getParameter("username");

        String remember = request.getParameter("remember");

        response.setCharacterEncoding("UTF-8");

        response.setContentType("text/html;charset = UTF-8");

        PrintWriter out = response.getWriter();
//创建一个新的Cookie

        Cookie cookie = new Cookie("username", username);

        cookie.setPath(request.getContextPath());

        if(remember != null){

            //如果选择了记住用户名，则设置Cookie的有效期为一个不为0的整数

            cookie.setMaxAge(Integer.MAX_VALUE);

        }else{

            //否则则把有效期设置为0，即命令浏览器删除该cookie

            cookie.setMaxAge(0);

        }

        //将cookie对象添加到response对象中，这样服务器在输出response对象中的内容时就会把cookie也输出到客户端服务器

        response.addCookie(cookie);

        out.write("登录成功！");

    }
public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doGet(request, response);

    }

}

结果：

输入用户名和密码，选择记住用户名，然后点击登录。

页面显示登录成功！

重新打开浏览器，再次访问登录界面，会显示如图。