@Override
  public TransactionId getTransactionId() {
    TXStateProxy t = getTXState();
    TransactionId ret = null;
    if (t != null) {
      ret = t.getTransactionId();
    }
    return ret;
  }
Gets the current transaction identifier or null if no transaction exists
geode-core/src/main/java/org/apache/geode/internal/cache/TXManagerImpl.java