code: public void connectionClosed(javax.sql.ConnectionEvent event) {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEventEnabled())
              Tr.event(this, tc, "connectionClosed", "Notification of connection closed received from the JDBC driver", AdapterUtil.toString(event.getSource()));
  
          // We have intentionally removed our connection event listener prior to closing the
          // underlying connection. Therefore, if this event ever occurs, it indicates a
          // scenario where the connection has been closed unexpectedly by the JDBC driver
          // or database. We will treat this as a connection error.
          if(isAborted()) {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled())
                  Tr.debug(this, tc, "The connection was aborted, so this event will not be processed");
          } else {
              processConnectionErrorOccurredEvent(null, event.getSQLException());
          }
      }
docs: Invoked by the JDBC driver when the java.sql.Connection is closed.
  
  @param event a data structure containing information about the event.