java下载HTML文件的问题！！！急！！！！

试一试这个import java.io.*;
public class FileDownLoad {  public FileDownLoad() {
  }
  public void fileDown(String aFileName,javax.servlet.http.HttpServletResponse response) throws Exception {
    java.io.BufferedInputStream iin;
    BufferedOutputStream dout;
    try {
       File ff=new File(aFileName);
       if(!ff.exists()){
         throw new Exception("对不起! 您下载的文件不存在");
       }else{
         byte[] buffer;
         int length=(new Long(ff.length())).intValue();
         buffer=new byte[length];
         try{
             iin=new BufferedInputStream(new java.io.FileInputStream(ff));
              //设置类型和头信息
            response.setContentType( "application/octet-stream" ); // MIME type for pdf doc
            int pos=aFileName.lastIndexOf("/");
            aFileName=aFileName.substring(pos+1);
            System.out.println(aFileName);
            response.setHeader("Content-disposition", "attachment; filename="+aFileName);
            //传送数据
            dout = new BufferedOutputStream( response.getOutputStream());
            int once = 0;
            int total = 0;
            while ((total<length) && (once>=0)) {
               once = iin.read(buffer,total,length);
               total += once;
               dout.write(buffer,0,length);
            }
            if(iin!=null){   iin.close();}
            if(dout!=null){  dout.close();}
          }catch(Exception ex){
             throw new Exception("文件下载过程中出现错误! ");
          }
        }
      }catch(Exception ex) {
         throw new Exception("文件下载过程中出现错误! ");
      }
   }
}