Problem on downloading a zip file

Question

I am having a problem on downloading a zip file(file size is about 2Mb). Sometimes I can get a complete file and can open the file, sometimes the zip file is chunked(the file size is smaller than the right one), so I can't open it.
The file content is stored in a blob field. The code first goes to database get the blob as inputstream, then copy the inputstream into response.getOutputStream().
The problem is unpredictable. Even for the same blob data, sometimes I can get working file, sometimes I just get crapped file.
Could somebody help me out? I am struggling with it.
Any input is appreciated!
public class DownloadTextAction extends Action implements Serializable{
    private static Log log = LogFactory.getLog(DownloadTextAction.class);
    public ActionForward execute(ActionMapping mapping, ActionForm form,
                                 HttpServletRequest request,
                                 HttpServletResponse response) throws Exception
        ActionErrors errors = new ActionErrors();
        String batch_id = (String)request.getParameter("batch_id");
        String fileName = batch_id+".zip";
        try
//          response.setContentType("application/octet-stream");
          response.setContentType("application/download");
  //        response.setContentLength(content.length());
//          response.setHeader("Content-Disposition", "inline; filename=\""
//                    + fileName + "\"");
          response.setHeader("Content-Disposition", "attachment; filename=\""
                    + fileName + "\"");
          InputStream in = untilService.getBlob(batch_id);         
          OutputStream out = response.getOutputStream();
          FileHelper.copy(in, out);
          out.flush();
          in.close();
          out.close();
        catch (Exception e)
          errors.add(ActionErrors.GLOBAL_ERROR, new ActionError("error.detail", e.toString()));
          saveErrors(request, errors);
          log.error(e.toString());      
        return mapping.findForward(Constants.SUCCESS);
    }

Answer 1

Maybe a fault in the missing FileHelper.copy() method?