docs: @Override
      public String getResolvedUserid()
                      throws SIConnectionUnavailableException, SIConnectionDroppedException,
                      SIErrorException
      {
          if (TraceComponent.isAnyTracingEnabled() && CoreSPIConnection.tc.isEntryEnabled())
              SibTr.entry(CoreSPIConnection.tc, "getResolvedUserid", this);
  
          // See if this connection has been closed
          checkNotClosed();
  
          String userName = null;
          try {
              if (_subject != null)
                  userName = runtimeSecurityService.getUniqueUserName(_subject);
          } catch (MessagingSecurityException mse) {
              // No FFDC Needed here, just log an exception
              if (CoreSPIConnection.tc.isDebugEnabled())
                  SibTr.exception(tc, mse);
          }
  
          if (TraceComponent.isAnyTracingEnabled() && CoreSPIConnection.tc.isEntryEnabled())
              SibTr.exit(CoreSPIConnection.tc, "getResolvedUserid", userName);
  
          return userName;
      }