What version of Jess are you using? For the most current version, the
only thing I see that could possibly give that stack trace would be if
the PropertyChangeEvent event object being sent to Jess was itself
null, but that seems unlikely given that you're using
PropertyChangeSupport. If you're using some older version, perhaps
you're seeing an old bug that's already been fixed.
On Aug 23, 2009, at 5:00 PM, Pierre Bezuhov wrote:
As I said before, the firePropertyChange method was ineffective.
Now however, after changing around some code (none of the code
listed in this post), I'm getting the following error when
firePropertyChange is called.
java.lang.NullPointerException
at jess.de.propertyChange(Unknown Source)
at
java
.beans
.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:
339)
at
java
.beans
.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:
276)
at geogame.server.Round.setRound(Round.java:61)
at geogame.server.Game.advanceRound(Game.java:987)
at geogame.server.Game.advanceTimer(Game.java:910)
at geogame.server.Game.run(Game.java:889)
at
com.sun.sgs.impl.service.task.PendingTask.run(PendingTask.java:224)
at com.sun.sgs.impl.service.task.TaskServiceImpl
$TaskRunner.run(TaskServiceImpl.java:1081)
at
com
.sun
.sgs
.impl
.kernel
.TransactionSchedulerImpl.executeTask(TransactionSchedulerImpl.java:
579)
at com.sun.sgs.impl.kernel.TransactionSchedulerImpl.access
$500(TransactionSchedulerImpl.java:70)
at com.sun.sgs.impl.kernel.TransactionSchedulerImpl
$TaskConsumer.run(TransactionSchedulerImpl.java:487)
at java.util.concurrent.Executors
$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask
$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor
$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor
$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
I thought that maybe this meant that the object for which
firePropertyChange was being called was not added to the engine.
However I verified that a Round object is being added and that the
corresponding fact shows up. Anyone know what's going on here?
On Fri, Aug 21, 2009 at 11:48 AM, Ernest Friedman-Hill <[email protected]
> wrote:
The only thing here that's clearly wrong is the equals() method --
you can't (generally) compare Strings with equals -- you want to use
the equals() method instead. But otherwise from Jess's perspective I
think things should be fine.
How are you adding the objects to working memory? Using "add" or
"definstance"? Can I see that line of code?
On Aug 21, 2009, at 11:20 AM, Pierre Bezuhov wrote:
When I call firePropertyChange from my Java object after setting an
attribute the working memory of my engine is not updated. I know
this because I loop through the facts before and after the setting
of the attribute, and "round" is set to "0" both times.
My Java and Jess code is below (if you're wondering why I have a
class just to wrap an int and string, it's to tie into some 3rd
party code I don't have control over). Any idea what I'm doing wrong?
######## JAVA CLASS ########
package game.server;
import java.beans.*;
import java.io.*;
import java.nio.*;
import java.util.*;
import jess.*;
public class Round implements Serializable
{
private static final long serialVersionUID = 1L;
private int round;
private String gameName;
private PropertyChangeSupport propertyChange;
protected Round(int round, String game)
{
this.round = round;
gameName = game;
propertyChange = new PropertyChangeSupport(this);
}
public int getRound()
{
return round;
}
public void setRound(int round)
{
if (this.round != round)
{
int oldValue = this.round;
this.round = round;
// Fire property change event so Jess working memory is
updated
propertyChange.firePropertyChange("round", new
Integer(oldValue), new Integer(this.round));
}
}
public String getGameName()
{
return gameName;
}
public void setGameName(String game)
{
gameName = game;
}
public void addPropertyChangeListener(PropertyChangeListener
listener)
{
propertyChange.addPropertyChangeListener(listener);
}
public void removePropertyChangeListener(PropertyChangeListener
listener)
{
propertyChange.removePropertyChangeListener(listener);
}
public boolean equals(Object obj)
{
boolean equal = false;
if (obj instanceof Round)
{
Round objRound = (Round)obj;
equal = ((objRound.getRound() == round) &&
(objRound.getGameName() == gameName));
}
return equal;
}
public int hashCode()
{
// Game name never changes so hashCode is mutable
return gameName.hashCode();
}
}
######## JESS RULES ########
(import game.server.*)
(deftemplate Round (declare (from-class Round)))
(defrule process-round
(Round {round >= 0} (round ?round))
=>
(printout t "Round " ?round crlf)
)
---------------------------------------------------------
Ernest Friedman-Hill
Informatics & Decision Sciences, Sandia National Laboratories
PO Box 969, MS 9012, Livermore, CA 94550
http://www.jessrules.com
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Ernest Friedman-Hill
Informatics & Decision Sciences, Sandia National Laboratories
PO Box 969, MS 9012, Livermore, CA 94550
http://www.jessrules.com
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