"Nested exception is: null" means that the *message* in the nested
exception is null; this is often the case for several kinds of
exceptions thrown by the JVM itself, NullPointerExceptions being the
most common. If you have access to the Exception object itself, then
use theException.getCause().printStackTrace() to display the trace of
this nested exception -- it will give you a lot more information about
what's really happening.
Swing is touchy because you're only supposed to work with it on the
GUI event processing thread; calling Swing methods directly from any
of your Jess/Protege code likely violates this prescription, and
that's one possible source of these errors. You need to be aware of
threading issues any time you're working with Swing, using Jess/
Protege or in any other situation.
On Nov 13, 2009, at 1:38 AM, Patricia Charlton wrote:
Hi there,
Thanks for this. Sorry about the lack of details but the error
occurred in a number of places and not consistently with testing. So
while it seemed like a "null pointer" of sorts it didn't seem to be
from the JESS code and seemed to be some protege/owl problem.
Further testing and reviewing of the log file from Protege shows
some conflict between running JESS from protege and calling JAVA
SWING methods.
It might be the way I call these methods but it seems to be a
protege/SWING problem and not JESS itself. When I run my engine via
Java methods or from the JESS command line without protege the
problems don't appear (at least for now).
I'm guessing that calling SWING methods from JESS via the protege
environment was never intended?
Kind regards,
Patricia
On 12 Nov 2009, at 09:15, Wolfgang Laun wrote:
Without any information about your facts (shadow or not) and rules
only very general suggestions are possible.
NPE's may come up when a slot usually holding an object is null and
you call a method.
Less obvious are cases when a java.lang.Integer (or similar) is
null and the value is used in an arithmetic operation or a
comparison; then unboxing causes the NPE.
-W
On Mon, Nov 9, 2009 at 10:29 AM, Patricia Charlton <patricia.charl...@pobox.com
> wrote:
Hi there,
I'm developing an inference engine using JESS. I am using protege
and JESS TAB integration and running JESS from the protege
environment.
Occasionally I get an error nested exception is: null. It does not
happen each time I run the application and I have tested each part
independently. It is also not always with the same inference about
a particular concept.
Is there a known problem between the integration environment where
for example concept pointers may get dropped?
I am currently at a loss as to how to fix this. It maybe a problem
with protege/jess or jess tab.
(current environment is MAC, Protege 3.4 and Jess 7.1)
Any help or pointers at this stage would be great.
Kind regards,
Patricia
--------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users y...@address.com
'
in the BODY of a message to majord...@sandia.gov, NOT to the list
(use your own address!) List problems? Notify owner-jess-us...@sandia.gov
.
--------------------------------------------------------------------
---------------------------------------------------------
Ernest Friedman-Hill
Informatics & Decision Sciences, Sandia National Laboratories
PO Box 969, MS 9012, Livermore, CA 94550
http://www.jessrules.com
--------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users y...@address.com'
in the BODY of a message to majord...@sandia.gov, NOT to the list
(use your own address!) List problems? Notify owner-jess-us...@sandia.gov.
--------------------------------------------------------------------
