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Session案例用户登录

2017-04-09 19:28 471 查看

一.Session案例思维导图

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>

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>

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>

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);
}
}
}