def preloadObjProperty(self, REQUEST, RESPONSE=None):
      """ ObjAttrs.preloadObjProperty """
      content_type = 'text/plain'
      message = '{"success":true}'
      # Additional parameters.
      for qs in REQUEST['QUERY_STRING'].split('&'):
        e = qs.find('=')
        if e >= 0:
          k = qs[:e]
          v = qs[e+1:]
          REQUEST.set(k,v)

      # Mandatory parameters.
      lang = REQUEST['lang']
      key = REQUEST['key']

      dataRequestKey = REQUEST.get('dataRequestKey')
      filenameUnescape = REQUEST.get('filenameUnescape')
      if dataRequestKey:
        value = REQUEST[dataRequestKey]
        if isinstance(value,ZPublisher.HTTPRequest.FileUpload):
          filename = value.filename
        else:
          filename = value
          value = REQUEST['BODY']
          if filenameUnescape:
            filename = _globals.unescape(filename)
      else:
        value = REQUEST['userfile[0]']
        filename = value.filename
      blob = self.ImageFromData(value,filename)
      filename = blob.getFilename()

      # Preload to temp-folder.
      session_id = REQUEST['session_id']
      form_id = REQUEST['form_id']
      temp_folder = self.temp_folder
      id = session_id + '_' + form_id + '_' + key
      if id in temp_folder.objectIds():
        temp_folder.manage_delObjects([id])
      meta_id = REQUEST.get('meta_id',self.meta_id)
      obj_attr = self.getObjAttr(key,meta_id)
      datatype = obj_attr['datatype_key']
      if datatype == _globals.DT_IMAGE:
        file = temp_folder.manage_addImage( id=id, title=filename, file=value)
      else:
        file = temp_folder.manage_addFile( id=id, title=filename, file=value)

      if REQUEST.get('set'):
        self.setReqProperty(key,REQUEST)
        message = self.getZMILangStr( 'MSG_UPLOADED')+'('+self.getLangFmtDate(time.time())+')'

      # Return with success.
      RESPONSE.setHeader('Content-Type',content_type)
      return message