Session案例用户登录

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一.Session案例思维导图

思维导图

二.编写登录页面：login.jsp

实现登录功能和显示登录错误信息

1.登录页面
2.显示登录失败信息
3.默认账户：mahaun 密码：123456

<%--  Created by IntelliJ IDEA.  User: pc  Date: 17-4-4  Time: 下午6:01  To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>登录页面</title></head><body><%    if(null!=request.getAttribute("Ext")){        out.print("<h3 style=' color: red'>"+request.getAttribute("Ext")+"</h3>");    }%><h3 >登录页面<h3>    <form action="/LoginServlet" method="post">        用户名：<input type="text" name="username"/>        密  码：<input type="password" name="password">        <input type="submit" value="登录">-    </form></body></html>

登录页面

登录失败时

三.编写登录成功和再次访问页面：index.jsp index2.jsp

1.登录成功显示用户名

2.再次访问显示用户名

index.jsp:

1.显示登录成功
2.显示登录的用户名密码
3.判断session中是否含有username

<%--  Created by IntelliJ IDEA.  User: pc  Date: 17-4-4  Time: 下午6:01  To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html>  <head>    <title>$Title$</title>  </head>  <body>  <%    String username=(String)session.getAttribute("username")    if(null==username){        response.sendError(404);    }else {  %>  <h1>主页面1</h1>  <h3>用户名：<%=request.getSession().getAttribute("username") %></h3>  恭喜登录成功！  </body><%  }%></html>

登陆成功

index2.jsp:

1.通过Session显示用户名
2.判断session中是否含有username
3.显示用户再次访问信息从 session中访问到username

<%--  Created by IntelliJ IDEA.  User: pc  Date: 17-4-4  Time: 下午6:02  To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>主页2</title></head><body><%    String username=(String)session.getAttribute("username")    if(null==username){        response.sendError(404);    }else {%><h1>主页面2</h1><h3>用户名：<%=request.getSession().getAttribute("username") %></h3>欢迎<%=request.getSession().getAttribute("username") %>再次访问！</body><%    }%></body></html>

再次访问

三.写Servlet类

里面包含：接受用户名和密码

1.校验是否登录成功
2.重定向到index.jsp
3.创建Session:setAttribute:保存username
4.转发到login页面，request保存失败信息
5.创建reques：setAttribute保存要输出的错误信息

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 java.io.IOException;/** * Created by pc on 17-4-4. */@WebServlet(name = "Login_Servlet",urlPatterns = "/LoginServlet")public class LoginServlet extends HttpServlet {    protected void doPost(HttpServletRequest request, HttpServletResponse response)        throws ServletException, IOException {        request.setCharacterEncoding("utf-8");        response.setContentType("text/html;charset=utf-8");        String username = request.getParameter("username");        String password = request.getParameter("password");        if("mahuan".equals(username)&&"123456".equals(password)){            //登录成功            request.getSession().setAttribute("username",username);            response.sendRedirect(request.getContextPath()+"/index.jsp");        }else {            //登录失败            request.setAttribute("Ext","您的账户或密码有误，请重新登录！");            request.getRequestDispatcher("/login.jsp").forward(request,response);        }    }}