issue with trapped exception

[Luis Bernardo]

Hello,

I am using FOP and FOP uses Xalan. I am facing an issue where FOP
enters in an infinite loop. Upon further investigation I found out
that FOP throws an exception before the code reaches the infinite loop
but that exception is trapped by Xalan. The relevant Xalan code is
this one, in org.apache.xalan.templates.ElemLiteralResult.execute():


        catch (TransformerException te)
        {
            // thrown in finally to prevent original exception
consumed by subsequent exceptions
            tException = te;
        }
        catch (SAXException se)
        {
            tException = new TransformerException(se);
        }

        try
        {
            /* we need to do this endElement() to balance the
             * successful startElement() call even if
             * there was an exception in the middle.
             * Otherwise an exception in the middle could cause a
system to hang.
             */
            if (transformer.getDebug()) {
                // flush any buffered pending processing before
                // the trace event.
                //rhandler.flushPending();
                transformer.getTraceManager().fireTraceEndEvent(this);
            }
            rhandler.endElement(getNamespace(), getLocalName(), getRawName());
        }

The tExeption holds the exception thrown by FOP. But then Xalan goes
and calls rhandler.endElement(getNamespace(), getLocalName(),
getRawName()) and that ultimately triggers the infinite loop in FOP. I
see the above comment that seems to indicate there is a good reason
why Xalan needs to hold the exception before re-throwing it, but in
this case the result is not nice since rhandler.endElement() never
returns. Since FOP throws an exception that would have avoided the
infinite loop I don't know whether to blame FOP of Xalan.

Can you please give me an explanation why the above Xalan code is
necessary? Why would the system potentially hang if the exception was
not trapped above?

Thanks,
Luis