<html:form action="/upload.do?from=sender" method="post" enctype="multipart/form-data">
   <html:file property="fichier"/>
   ...
</html:form>

public class UploadActionForm extends ActionForm
{
   protected FormFile file;

   public FormFile getFile() 
   {   
      return file;
   }

   public void setFile(FormFile file) 
   {
      this.file = file;
   }
   ...
}

{
   ...
   UploadActionForm theForm = (UploadActionForm) actionForm;
   FormFile file = theForm.getFichier();
   ...
}

response.setContentType("multipart/zip"); 
response.setHeader("Content-Disposition",
                   "attachment; filename=\"" + 
                   filename.trim().substring(1,filename.length()) + "\";"); 
response.setContentLength((int)f.length()); 

try
{
      OutputStream os = response.getOutputStream();
      FileInputStream stream = new FileInputStream(f);
      BufferedInputStream  bis = new BufferedInputStream(stream);
      InputStream is = new BufferedInputStream(bis);
      int count;
      byte buf[] = new byte[4096];
      while ((count = is.read(buf)) > -1)
      {
          os.write(buf, 0, count);
      }
      is.close(); 
      os.close();
}
catch (Exception ex)
{ 
   ex.printStackTrace();
}
..
return mapping.findforward("fichieenvoye");

<html:link page="/openpdf.do"
           name="pdfForm"
           property="pdfName"
           target="_blank">
   <html:img src="./images/PDF.gif" border="0" alt="View PDF"/>
</html:link>

ByteArrayOutputStream bos = new ByteArrayOutputStream(5000);
// Remplir ici votre bos avec le flux du PDF 


httpServletResponse.setContentType("application/pdf");
httpServletResponse.setContentLength(bos.size());

OutputStream os = httpServletResponse.getOutputStream();
os.write(bos.toByteArray(), 0, bos.size());
os.flush();
os.close();

return null;