public Response descOneColumn(String user, String db, String table, String column)
    throws SimpleWebException, NotAuthorizedException, BusyException,
    ExecuteException, IOException {
    Response res = listColumns(user, db, table);
    if (res.getStatus() != HttpStatus.OK_200)
      return res;

    Object o = res.getEntity();
    final Map fields = (o != null && (o instanceof Map)) ? (Map) o : null;
    if (fields == null)
      throw new SimpleWebException(HttpStatus.NOT_FOUND_404, "Internal error, unable to find column "
        + column);


    List<Map> cols = (List) fields.get("columns");
    Map found = null;
    if (cols != null) {
      for (Map col : cols) {
        if (column.equals(col.get("name"))) {
          found = col;
          break;
        }
      }
    }
    if (found == null)
      throw new SimpleWebException(HttpStatus.NOT_FOUND_404, "unable to find column " + column,
        new HashMap<String, Object>() {
          {
            put("description", fields);
          }
        });
    fields.remove("columns");
    fields.put("column", found);
    return Response.fromResponse(res).entity(fields).build();
  }
Return a json description of one column.
hcatalog/webhcat/svr/src/main/java/org/apache/hive/hcatalog/templeton/HcatDelegator.java