@GET
  @Path("/empty-regioninfo")
  public List<HbckEmptyRegionInfo> getEmptyRegionInfo() {
    return catalogJanitorReport.getEmptyRegionInfo().stream()
      .map(obj1 -> new HbckEmptyRegionInfo(Bytes.toString(obj1))).collect(Collectors.toList());
  }
The root object exposing hbck.jsp page as JSON Output.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/http/hbck/resource/HbckMetricsResource.java