登陆问题

如果我验证不正确,跳到connect,怎样才能不跳到别的页面.<%@ page contentType="text/html; charset=gb2312" %>
　<html> 
　　<body BGCOLOR="#186FA6"> 
     <title>用户登陆</title>       <form name="login" method="post" action="connect.jsp">   <table width="203" border="0"  cellpadding="5" cellspacing="0" >
     <tr> 
                  <td width="67"><FONT FACE="宋体" size="3" color="#ffffff">用户名：</FONT></td>
                  <td width="114"><input name="name" type="text" id="name" size="15"></td>
            </tr>
             <tr> 
                    <td><FONT FACE="宋体" size="3" color="#ffffff">密码：</FONT></td>
                    <td><input name="passwd" type="password" id="passwd" size="15"></td>
              </tr>
              <tr> 
                        <td>&nbsp;</td>
                        <td><input type="image" SRC="images/but_001.gif" onclick="submit()" BORDER=0> 
                            <input  type="image" SRC="images/but_003.gif" onclick="Close()" BORDER=0 ></td>
              </tr>
         </table>　　</body> 
　　</html>   <script language="javascript">    function Close()
    {
window.close();
    }
   </script>connect.jsp
<%@ page contentType="text/html; charset=gb2312" %>
<%@ page import="java.sql.*" %>
<%@ page import="java.util.*" %>
<%String Username=request.getParameter("name");
String Userpasswd=request.getParameter("passwd");
System.out.println(Username); if (Username=="" ||Userpasswd=="")
%>
<script language="javaScript">
alert("您输入的用户名或者密码为空，请重新输入！")
window.history.back();
</script>
　<%
   Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver").newInstance();
   String url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=sde";    String user="sa"; 
String password="sa";
Connection conn= DriverManager.getConnection(url,user,password);
Statement stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);  String sql="select * from login where Username like '"+Username+"'"; ResultSet rs=stmt.executeQuery(sql);

   while(rs.next()){      String name=rs.getString(1);        String Password=rs.getString(2);     System.out.println(!conn.isClosed()); System.out.println(Username); }
%>