When the optional element <transaction-timeout> is not set in the jboss.xml, a (debug) message is logged with the text "Ignoring transaction-timeout 'null'" - stange message for an optional element that is not there .
What is even worse is that a stacktrace is printed of the NumberFormatException that occurred when trying to parse this null value. These stacktraces clutter the server.log, for example in my case these stacktraces are responsible for 50% of the size of the (debug) log file.

This behaviour is caused by the following fragment from BeanMetaData:

String txTimeout = getOptionalChildContent(maNode, "transaction-timeout");
try

{ ma.txTimeout = Integer.parseInt(txTimeout); }

catch (Exception ignore)

{ log.debug("Ignoring transaction-timeout '" + txTimeout + "'", ignore); }

Of course, this should be: if (txTimeout != null) a.txTimeout = Integer.parseInt(txTimeout);