tds/src/main/java/thredds/core/TdsRequestedDataset.java
public GridDataset openAsGridDataset(HttpServletRequest request, HttpServletResponse response) throws IOException {
    return isRemote ? ucar.nc2.dt.grid.GridDataset.open(path) : datasetManager.openGridDataset(request, response, path);
  }
public GridDataset openAsGridDataset(HttpServletRequest request, HttpServletResponse response) throws IOException {
    return isRemote ? ucar.nc2.dt.grid.GridDataset.open(path) : datasetManager.openGridDataset(request, response, path);
  }
return null means request has been handled, and calling routine should exit without further processing