private synchronized void afterPrepare() {
   if (operations != null) {
     for (TransactionOperation operation : operations) {
       operation.afterPrepare(this);
     }
   }
 }
 private synchronized void beforeRollback() throws Exception {
   if (operations != null) {
     for (TransactionOperation operation : operations) {
       operation.beforeRollback(this);
     }
   }
 }