Cookie应用案例——记住用户名

2018-04-08 本文已影响9人嗷老板

我们在网站上登陆的时候，一般都会有一个选择框，记住用户名，这个功能的实现方式就是使用cookie实现的。

完成这个案例我们需要三个页面：

LoginUIServlet 登录UI界面,只负责展示页面
LoginServlet 提交之后的跳转页面,负责处理逻辑判断
IndexServlet 登录成功之后的跳转页面

完成LoginUIServlet

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;

import com.itheima.cookie.CookieUtils;


public class LoginUIServlet extends HttpServlet {
   
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       //设置响应类型和编码
       response.setContentType("text/html;charset=UTF-8");
       //获取输出流对象
       PrintWriter out = response.getWriter();
       Cookie[] cookies = request.getCookies();
       Cookie cookie = CookieUtils.getCookie(cookies, "username");
       String username = "";
       String checked = "";
       
       //如果cookie存在，那么设置用户名和复选框选择状态
       if(cookie != null){
           username = cookie.getValue();
           checked = "checked = 'checked'";
       }
       
       //输出html页面
       out.println("<html>");
       out.println("<head>");
       out.println("<title>登录页面</title>");
       out.println("</head>");
       out.println("<body>");
       out.println("<form action='/web08/LoginServlet' method='post'>");
       out.println("用户名:<input type='text' name='username' value='"+username+"'/>");
       out.println("<br />");
       out.println("密码:<input type='text' name='password' />");
       out.println("<br />");
       out.println("<input type='submit' value='登录' />");
       out.println("<input type='checkbox' name='remember' value='1' "+checked+"/>记住用户名");
       out.println("</form>");
       out.println("</body>");
       out.println("</html>");
   }

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

}

完成LoginServlet

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 LoginServlet extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置响应类型和编码
        response.setContentType("text/html;charset=UTF-8");
        //获取输出流
        PrintWriter out = response.getWriter();
        
        //获取表单中的数据
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String remember = request.getParameter("remember");
        
        //判断用户名和密码是否正确
        if("zhangsan".equals(username) && "123456".equals(password)){
            //用户名和密码正确,返回提示信息，跳转到首页
            out.println("登陆成功！3秒后跳转到首页！");
            response.setHeader("Refresh", "3;URL=/web08/IndexServlet");
            
            //判断用户是否记住用户名
            if("1".equals(remember)){
                //用户需要记住用户名,则创建cookie对象保存用户名
                Cookie c = new Cookie("username",username);
                c.setMaxAge(Integer.MAX_VALUE);
                response.addCookie(c);
            }else{
                //用户不需要记住用户名
                Cookie c =new Cookie("username","");
                c.setMaxAge(0);
                response.addCookie(c);
            }
        }else{
            //用户名或者密码错误
            out.println("用户名或密码错误！3秒后跳转到登陆页面");
            response.setHeader("Refresh", "3;URL=/web08/LoginUIServlet");
        }
    }

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

}

完成简单的首页IndexServlet

import java.io.IOException;
import java.io.PrintWriter;

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


public class IndexServlet extends HttpServlet {
   
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置响应类型和编码
        response.setContentType("text/html;charset=UTF-8");
        //获取输出流对象
        PrintWriter out = response.getWriter();
        
        out.println("<h1>我是首页</h1>");
    }

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

}

案例实现结果

登录页面

登录成功

再次打开登录界面

Cookie应用案例——记住用户名

案例实现结果

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