Sent request parameters to UploadAction in gwt-upload

I get gwt-upload working in a GAE application. As suggested, I implemented a Custom UploadAction to handle the storage of the file in the DataStore. The code goes like this:

public String executeAction(HttpServletRequest request,
        List<FileItem> sessionFiles) throws UploadActionException {
    logger.info("Starting: DatastoreUploadAction.executeAction");
    String executeAction = super.executeAction(request, sessionFiles);

    for (FileItem uploadedFile : sessionFiles) {            
        Long entityId = new Long(2001); // This is where i wanna use a request parameter
        InputStream imgStream;
        try {
            imgStream = uploadedFile.getInputStream();
            Blob attachment = new Blob(IOUtils.toByteArray(imgStream));
            String contentType = uploadedFile.getContentType();
            appointmentDao.setAppointmentAttachment(entityId, attachment,
                    contentType);
        } catch (IOException e) {
            logger.error("Unable to store file", e);
            throw new UploadActionException(e);
        }

    }

    return executeAction;
}

As you see, the DAO class requires the "EntityID" to store the uploaded file in the DataStore. Now i'm working with a hard-coded value and it goes fine, but i'd like to have the entityID sent by the client as a request parameter. The widget that does the upload is a MultiUploader:

private MultiUploader defaultUploader;

Is it posible to the MultiUploader -or any other Widget- to set a request parameter so i can use it in my UploadAction?

Yes, you can set it on your client-side code.
There is method: MultiUploader #setServletPath(java.lang.String), for example:

  final MultiUploader u = new MultiUploader();
  ...
  ...
  ...
  u.setServletPath(u.getServletPath() + "?entityId="+myObject.getEntityId());

on server side:

  String entityId= request.getParameter("entityId"); 

Read this for more information: Sending additional parameters to the servlet