public static synchronized void registerTransactionServicePlugin(TransactionServicePlugin l){
  if (service_ != null) {
    service_.addTSListener(l);
  }
  tsListenersList_.add(l);
}

public static synchronized void registerTransactionServicePlugin ( TransactionServicePlugin l ) { if ( service_ != null ) { service_ . addTSListener ( l ) ; } tsListenersList_ . add ( l ) ; }
add a transaction service listener .
