private QueryStringEncoder buildFirstPageEncoder() {
    final QueryStringEncoder encoder = new QueryStringEncoder(request.getRequestURI());
    addParam(encoder, NAME_PARAM, name);
    addParam(encoder, SCAN_LIMIT_PARAM, scanLimit);
    addParam(encoder, SCAN_REGION_STATE_PARAM, scanRegionState);
    addParam(encoder, SCAN_TABLE_PARAM, scanTable);
    return encoder;
  }
Adds {@code value} to {@code encoder} under {@code paramName} when {@code value} is non-null.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/http/MetaBrowser.java