@GET
  @Path("/region-holes")
  public List<HbckRegionHoles> getRegionChainHoles() {
    return catalogJanitorReport.getHoles().stream()
      .map(obj1 -> new HbckRegionHoles(parseRegionInfo(obj1.getFirst()),
        parseRegionInfo(obj1.getSecond())))
      .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