【JavaWeb】利用Session保存用户登录信息

上一篇博客提到，为了安全起见，session常常用来保存用户的登录信息。那么服务器是怎么来实现的呢？这里我简单模拟一下。

第一步，编写登录主页：

<!DOCTYPE html>
<html>
<head>
<title>登陆页面</title>

<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">

<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->

</head>

<body>
<form action="/JavaWeb/LoginServlet" method="post">
        用户名：<input type="text" name="userName"/>
<br/>
        密码： <input type="text" name="userPwd"/>
<br/>
<input type="submit" value="登陆"/>
</form>
</body>
</html>

第二步，创建LoginServlet类，因为是为了获取服务端资源信息，所以这里用doGet方法来处理请求。实际处理过程肯定是需要查询数据库中的用户信息的，这里简化了，旨在了解Session的用法即可。

package gz.itcast;

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;
import javax.servlet.http.HttpSession;

public class LoginServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");

//接收参数
        String userName = request.getParameter("userName");
        String userPwd = request.getParameter("userPwd");

//判断登陆是否成功
if(userName.equals("刘小斌") && userPwd.equals("123456")) {
//登陆成功

//创建session对象
            HttpSession session = request.getSession();
//把用户数据保存在session域对象中
            session.setAttribute("loginName", userName);
//跳转到用户主页
            response.sendRedirect(request.getContextPath()+"/IndexServlet");
        } else {
//登陆失败，请求重定向
            response.sendRedirect(request.getContextPath() + "/fail.html");
        }
    }

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

}

为请求成功创建的IndexServlet类：

package gz.itcast;

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;
import javax.servlet.http.HttpSession;

public class IndexServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();

        String html = "";

//得到session对象
        HttpSession session = request.getSession(false);
if(session==null){
//没有登录成功，跳转到登录页面
            response.sendRedirect(request.getContextPath()+"/login.html");
return;
        }

//取出会话数据
        String loginName = (String)session.getAttribute("loginName");
if(loginName==null){
//没有登录成功，跳转到登录页面
            response.sendRedirect(request.getContextPath()+"/login.html");
return;
        }

        html = "<html><body>欢迎回来，" +loginName+ "</a></body></html>";


        writer.write(html);
    }

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

为请求失败创建的失败页面：

<!DOCTYPE html>
<html>
<head>
<title>信息提示页面</title>

<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">

<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->

</head>

<body>
<font color = red size = 3>用户名或密码输入错误！请重新输入。</font>
</br></br>
<a href="/JavaWeb/login.html">返回登陆页面，重新输入。</a>
</body>
</html>