code: @Override
  	public void close() {
  		if (conn != null) {
  			LOG.trace("Close connection. conn[{}], hashCode[{}]", conn, conn.hashCode());
  			try {
  				conn.close();
  			} catch (SQLException e) {
  				throw new UroborosqlSQLException(e);
  			}
  			conn = null;
  		}
  	}
docs: {@inheritDoc}
  
  @see jp.co.future.uroborosql.connection.ConnectionManager#close()