java导出excel文件时，如何进行直接打开文件，不用弹出下载的提示。

 /**
 * 下载
 * 
 * @return
 */
public String down() {
try {

  
   filename=changechar(filename);
   filenameweb=changechar(filenameweb);
   String webPath="";
   //真正用户名
           String realFilename="";
           String[] filenameArray=null;
           if(filenameweb.trim().equalsIgnoreCase(""))
           {
              filenameArray=filename.split("[/]");
              realFilename=filenameArray[filenameArray.length-1];
              //取配置文件的webpath信息
  InputStream is = getClass().getResourceAsStream("/db.properties");
  Properties dbProps = new Properties();
  dbProps.load(is);
  // webPath = dbProps.getProperty("Titans.webPath", "");
  dbProps = null;
          filename="/"+filename;
           }else
           {                webPath=request.getRealPath("");
               filenameArray=filenameweb.split("[/]");
               realFilename=filenameArray[filenameArray.length-1];
            filenameweb=webPath+"/"+filenameweb;
            filename=filenameweb;
           }
       int i=65000;
       java.io.File file = new java.io.File(filename);
       java.io.FileInputStream fileinputstream = new java.io.FileInputStream(file);
       long l = file.length();
       if(l==0)
       {
         l = 1;
       }
       boolean flag = false;
       int k = 0;
       byte abyte0[] = new byte[i];
       response.setContentType("application/x-msdownload");
       String m_contentDisposition;
       m_contentDisposition = new String();
       m_contentDisposition=null;
       response.setContentLength((int)l);
       m_contentDisposition = m_contentDisposition != null ?
       m_contentDisposition : "attachment;";
       try
       {
         //取扩展名
      String extFilename ="";
         int a;
 a=realFilename.lastIndexOf(".");
             if (a>0)
 {
              extFilename=realFilename.substring(a+1).toUpperCase().trim();
 }
             //取主文件名
             String mainFilename="";
             int b;
             b=realFilename.lastIndexOf(".");
             if (b>0)
             {
              mainFilename=realFilename.substring(0,b).toUpperCase().trim();
             }
             realFilename=mainFilename.substring(0,16)+"."+extFilename;
             realFilename=getFileName(filename);
       }catch( Exception er)
       {
        
       }
      
       response.setHeader("Content-Disposition", m_contentDisposition + " filename=" + ptoUtf8String(realFilename) );
      while((long)k < l)
       {
              int j = fileinputstream.read(abyte0, 0, i);
              k += j;
              if(j==-1)
              {
                 response.getOutputStream().write(abyte0, 0, 1);
                 k=1;
              }
             else
                 response.getOutputStream().write(abyte0, 0, j);
        }
        fileinputstream.close();
   
} catch (Exception e) {
ExceptionProcess ep = new ExceptionProcess();
ep.process(e, request);
log.error(e.getMessage());
}
finally
{
return null;
}
}