@Override
  public Map<ByteBuffer, ColumnDescriptor> getColumnDescriptors(ByteBuffer tableName)
    throws IOError, TException {

    Table table = null;
    try {
      TreeMap<ByteBuffer, ColumnDescriptor> columns = new TreeMap<>();

      table = getTable(tableName);
      TableDescriptor desc = table.getDescriptor();

      for (ColumnFamilyDescriptor e : desc.getColumnFamilies()) {
        ColumnDescriptor col = ThriftUtilities.colDescFromHbase(e);
        columns.put(col.name, col);
      }
      return columns;
    } catch (IOException e) {
      LOG.warn(e.getMessage(), e);
      throw getIOError(e);
    } finally {
      closeTable(table);
    }
  }
Note: this internal interface is slightly different from public APIs in regard to handling of
the qualifier. Here we differ from the public Java API in that null != byte[0]. Rather, we
respect qual == null as a request for the entire column family. The caller (
{@link #getVerTs(ByteBuffer, ByteBuffer, ByteBuffer, long, int, Map)}) interface IS consistent
in that the column is parse like normal.
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift/ThriftHBaseServiceHandler.java