in log4j-jakarta-jms/src/main/java/org/apache/logging/log4j/jms/appender/JmsManager.java [376:388]
private void createMessageAndSend(final LogEvent event, final Layout layout) throws JMSException {
final var eventMessage = event.getMessage();
final Message message;
if (eventMessage instanceof org.apache.logging.log4j.message.MapMessage<?, ?>) {
message = map((org.apache.logging.log4j.message.MapMessage<?, ?>) eventMessage, session.createMapMessage());
} else if (layout != null) {
message = session.createTextMessage(layout.toSerializable(event));
} else {
throw new UnsupportedOperationException("Unable to create a JMS message without a layout defined");
}
message.setJMSTimestamp(event.getTimeMillis());
messageProducer.send(message);
}