【JavaWeb】利用Session保存用戶登錄信息

上一篇博客提到，爲了安全起見，session常常用來保存用戶的登錄信息。那麼服務器是怎麼來實現的呢？這裏我簡單模擬一下。

第一步，編寫登錄主頁：

<!DOCTYPE html>
<html>
  <head>
    <title>登陸頁面</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">
        用戶名：<input type="text" name="userName"/>
        <br/>
        密碼： <input type="text" name="userPwd"/>
        <br/>
        <input type="submit" value="登陸"/>
    </form>
  </body>
</html>

第二步，創建LoginServlet類，因爲是爲了獲取服務端資源信息，所以這裏用doGet方法來處理請求。實際處理過程肯定是需要查詢數據庫中的用戶信息的，這裏簡化了，旨在瞭解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");

        //接收參數
        String userName = request.getParameter("userName");
        String userPwd = request.getParameter("userPwd");

        //判斷登陸是否成功
        if(userName.equals("劉小斌") && userPwd.equals("123456")) {
            //登陸成功

            //創建session對象
            HttpSession session = request.getSession();
            //把用戶數據保存在session域對象中
            session.setAttribute("loginName", userName);
            //跳轉到用戶主頁
            response.sendRedirect(request.getContextPath()+"/IndexServlet");
        } else {
            //登陸失敗，請求重定向
            response.sendRedirect(request.getContextPath() + "/fail.html");
        }
    }

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

}

爲請求成功創建的IndexServlet類：

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對象
        HttpSession session = request.getSession(false);
        if(session==null){
            //沒有登錄成功，跳轉到登錄頁面
            response.sendRedirect(request.getContextPath()+"/login.html");
            return;
        }

        //取出會話數據
        String loginName = (String)session.getAttribute("loginName");
        if(loginName==null){
            //沒有登錄成功，跳轉到登錄頁面
            response.sendRedirect(request.getContextPath()+"/login.html");
            return;
        }

        html = "<html><body>歡迎回來，" +loginName+ "</a></body></html>";


        writer.write(html);
    }

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

爲請求失敗創建的失敗頁面：

<!DOCTYPE html>
<html>
  <head>
    <title>信息提示頁面</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>用戶名或密碼輸入錯誤！請重新輸入。</font>
        </br></br>
        <a href="/JavaWeb/login.html">返回登陸頁面，重新輸入。</a>
  </body>
</html>