jodd-jtx/src/main/java/jodd/jtx/JtxTransactionManager.java
protected void associateTransaction(final JtxTransaction tx) {
		totalTransactions++;
		ArrayList<JtxTransaction> txList = txStack.get();
		if (txList == null) {
			txList = new ArrayList<>();
			txStack.set(txList);
		}
		txList.add(tx);	// add last
	}
protected void associateTransaction(final JtxTransaction tx) {
		totalTransactions++;
		ArrayList<JtxTransaction> txList = txStack.get();
		if (txList == null) {
			txList = new ArrayList<>();
			txStack.set(txList);
		}
		txList.add(tx);	// add last
	}
Associate transaction to current thread.