LoginServlet.java

import javax.servlet.*;
import java.io.*;
import javax.servlet.http.*;

public class LoginServlet extends HttpServlet
{
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
               throws ServletException,IOException
    {
        String action=req.getParameter("action");
        if("chk".equals(action))
        {
            String name=req.getParameter("user");
            String pwd=req.getParameter("password");
            if((name!=null) && (pwd!=null))
            {
                if(name.equals("majinzhu") && pwd.equals("1234"))
                { 
                    StringBuffer sb=new StringBuffer();
                    sb.append("username=");
                    sb.append(name);
                    sb.append("&password=");
                    sb.append(pwd);
                    Cookie cookie=new Cookie("userinfo",sb.toString());
                    cookie.setMaxAge(1800);
                    resp.addCookie(cookie);
                    resp.sendRedirect("greet2");
                    return;
                }
                else
                {
                    resp.setContentType("text/html;charset=gb2312");
                    PrintWriter out=resp.getWriter();
                    out.println("用户名或密码错误,请<a href=login2>重新登录</a>");
                    return;
                }
            }
        }
        else
        {
            resp.setContentType("text/html;charset=gb2312");
            PrintWriter out=resp.getWriter();
            out.println("<html>");
          
            out.println("<head><title>登录页面</title></head>");
            out.println("<body>");
            out.println("<p>");
            out.println("<form method=post action=login2?action=chk>");
      
            out.println("<table>");
          
            out.println("<tr>");
            out.println("<td>请输入用户名</td>");
            out.println("<td><input type=text name=user></td>");
            out.println("</tr>");
          
            out.println("<tr>");
            out.println("<td>请输入密码</td>");
            out.println("<td><input type=password name=password></td>");
            out.println("</tr>");
          
            out.println("<tr>");
            out.println("<td><input type=reset value=重填></td>");
            out.println("<td><input type=submit value=登录></td>");
            out.println("</tr>");
          
            out.println("</table></form></body></html>");      
            out.close();
        }
    }
  
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
               throws ServletException,IOException
    {
        doGet(req,resp);
    }
}

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