Servlet课程0425（四） Servlet实现简单用户登录验证

//登录界面
package com.tsinghua;import javax.servlet.http.*;
import java.io.*;public class Login extends HttpServlet{
    public void doGet(HttpServletRequest req, HttpServletResponse res)
    {            //业务逻辑
        try{
            //中文乱码
            //浏览器默认ISO-8859
            res.setContentType("text/html;charset=gbk");                        PrintWriter pw = res.getWriter();            //返回登录界面
            pw.println("<html>");
            pw.println("<body>");
            pw.println("<h1>登录界面</h1>");
            pw.println("<form action='loginCl' method=post>");
            pw.println("用户名<input type='text' name='username'/><br/>");
            pw.println("密码<input type='password' name='userpwd'/><br/>");
            pw.println("<input type='submit' value='loing' /><br/>");
            pw.println("</form>");
            pw.println("</body>");
            pw.println("</html>");        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }    }     //处理get请求
     //req用于获得客户端(浏览器)的信息
     //res用于向 客户端(浏览器)返回信息
    public void doPost(HttpServletRequest req, HttpServletResponse res)
    {        this.doGet(req,res);            }    }

LoginCl.java

//登录界面
package com.tsinghua;import javax.servlet.http.*;
import java.io.*;public class LoginCl extends HttpServlet{
    public void doGet(HttpServletRequest req, HttpServletResponse res)
    {            //业务逻辑
        try{            //接收用户名和密码
            String u  = req.getParameter("username");
            String p = req.getParameter("userpwd");
            //验证            if(u.equals("litao") && p.equals("litao")){
                //合法
                //跳转到welcome
                res.sendRedirect("wel");
            }
            else{
                //不合法
                //写你要到的Servlet的那个URL
                res.sendRedirect("login");
            }        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }    }     //处理get请求
     //req用于获得客户端(浏览器)的信息
     //res用于向 客户端(浏览器)返回信息
    public void doPost(HttpServletRequest req, HttpServletResponse res)
    {        this.doGet(req,res);            }    }

Welcome.java

//登录界面
package com.tsinghua;import javax.servlet.http.*;
import java.io.*;public class Welcome extends HttpServlet{
    public void doGet(HttpServletRequest req, HttpServletResponse res)
    {            //业务逻辑
        try{            PrintWriter pw = res.getWriter();            //返回登录界面
            pw.println("Welcome,hello");                    }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }    }     //处理get请求
     //req用于获得客户端(浏览器)的信息
     //res用于向 客户端(浏览器)返回信息
    public void doPost(HttpServletRequest req, HttpServletResponse res)
    {        this.doGet(req,res);            }    }

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