下载文件的servlet为什么会执行两遍？

修改后代码如下：
package office.servlet;
import javax.servlet.http.*; 
import javax.servlet.*;import java.sql.*;
import java.io.*;
import office.notify.*;public class showNotify extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response){
dosometing(request,response);
} public void doPost(HttpServletRequest request, HttpServletResponse response){
dosometing(request,response);
}
    public void dosometing(HttpServletRequest request, HttpServletResponse response){
    try{


    NotifyExec NotifyExec = new NotifyExec();
            String notifyid="";
            String strExt="";
            String sql = "";
            notifyid=request.getParameter("notifyid");
   strExt=NotifyExec.getOneNotifyExt(notifyid);
   System.out.println(strExt);
   sql = "select affix from of_notify where notifyid="+ notifyid ;
   System.out.println(sql);
   cscec.database.sysdbcon DB = new cscec.database.sysdbcon();
   ResultSet rs = DB.executeQuery(sql);
   while(rs.next())
{
  response.reset();     if(strExt.equalsIgnoreCase("doc"))
{
          response.setContentType("application/msword");
     }
else if(strExt.equalsIgnoreCase("xls"))
{
     response.setContentType("application/vnd.ms-excel");
      }
else if(strExt.equalsIgnoreCase("jpg"))
 {
     response.setContentType("image/jpeg");
       }
else if(strExt.equalsIgnoreCase("txt"))                         {
     response.setContentType("text/plain");
       }  
else if(strExt.equalsIgnoreCase("jpeg"))
 {
     response.setContentType("image/jpeg");
      }
else if(strExt.equalsIgnoreCase("gif"))
 {
     response.setContentType("image/gif");
       }
else if(strExt.equalsIgnoreCase("bmp"))
 {
     response.setContentType("image/bmp");
      }
else
 {
     response.setContentType("application/octet-stream");
     String fileName = "";
fileName = rs.getString("affix");
        response.setHeader("Content-Disposition", "filename=" + new String(fileName.getBytes(),"ISO-8859-1")); 
          } OutputStream sos = response.getOutputStream();
InputStream in = null;
in = rs.getBinaryStream("affix"); int len = 0;
byte[] b = new byte[1024];
while((len = in.read(b)) > 0)
{
sos.write(b,0,len);
}
b=null;
in.close();
//sos.flush();//
sos.close();
}
rs.close();
DB.close();
}catch(Exception ee){
  ee.printStackTrace();
}
    }}