TextParamPanel tp = new TextParamPanel(componentId,
model, new ResourceModel(paramLabel, paramLabel), required);
// if it can be a reference to the local filesystem make sure it's valid
if (paramName.equalsIgnoreCase("url")) {
tp.getFormComponent().add(new FileExistsValidator());
}
// make sure the proper value is returned, but don't set it for strings otherwise
// we incur in a wicket bug (the empty string is not converter back to a null)
// GR: it doesn't work for File neither.
// AA: better not mess with files, the converters turn data dir relative to