private void handleRuntimeException(final RuntimeException e, Expression expression) {
        messageBuffer.clear();
        messageBuffer.append("Expression '")
                .append(expression.getDebugId())
                .append("' threw a '")
                .append(e.getClass().getSimpleName())
                .append("' while matching");
        final String message = messageBuffer.toString();
        log(Severity.FATAL_ERROR, message, e);
        // We should never get exceptions here so log stack trace.
        LOGGER.error(message, e);
    }
Outputs a data element if required using the current match or another
stored match.
stroom-pipeline/src/main/java/stroom/pipeline/xml/converter/ds3/DS3Parser.java