String sql = "select 1 id, cursor(select level from dual connect by level >= 5) coll from dual";
try (Connection con = new JdbcConnection("oracle18").getConnection();
    PreparedStatement stmt = con.prepareStatement(sql);
    ResultSet rs = stmt.executeQuery()) {
  while (rs.next()) {
    int id = rs.getInt("id");
    // How to get the 'coll' value?
  }
}

public class CursorTypeHandler extends BaseTypeHandler<Map<String, Object>>{

  @Override
  public Map<String, Object> getNullableResult(ResultSet rs, String columnName) throws SQLException {
    Map<String, Object> result = new HashMap<>();
    try (ResultSet nestedRs = rs.getObject(columnName, ResultSet.class)){
      ResultSetMetaData rsmd = nestedRs.getMetaData();
      for (int i = 0; i < rsmd.getColumnCount(); i++) {
        String key = rsmd.getColumnName(i + 1);
        Object value = rs.getObject(i + 1);
        result.put(key, value);
      }
    }
    return result;
  }