JESS: FYI: Confusing error message

[Jan Willem Lokin-2]

Jess throws an error at me that I don't really understand. The error
trace as attached. My code used to work earlier, but this has happened
when I pulled up some common code from two related "...Track" classes
into a common "Track" superclass. What confuses me most is that the
IAE message specifically complains about '...modifiers "public"'. A
quick Google search and some guessing led me to conclude that Jess
requires that the superclass should have "public" rather than default
visibility. That makes sense, but it would be nice if it said so.

grtz

-+- JW -+-



Jess reported an error in routine DefinstanceList.updateMultipleSlots
        while executing (definstance SensorTrack (new
platformcoverage.SensorTrack ?p ?task-sensor))
        while executing defrule MAIN::create-SensorTrack
        while executing (call (engine) runUntilHalt)
        while executing deffunction run-until-halt
        while executing (run-until-halt).
  Message: Method is not accessible.
  Program text: ( run-until-halt )  at line 1 in file <eval pipe>.
        at jess.DefinstanceList.getSlotValueFromObject(DefinstanceList.java:326)
        at jess.DefinstanceList.setAllSlotValuesFromObject(DefinstanceList.java:303)
        at jess.DefinstanceList.createNewShadowFact(DefinstanceList.java:281)
        at jess.DefinstanceList.definstance(DefinstanceList.java:76)
        at jess.Rete.definstance(Rete.java:2268)
        at jess.Definstance.call(Definstance.java:54)
        at jess.FunctionHolder.call(FunctionHolder.java:35)
        at jess.Funcall.execute(Funcall.java:338)
        at jess.Defrule.fire(Defrule.java:395)
        at jess.Activation.fire(Activation.java:98)
        at jess.Agenda.run(Agenda.java:267)
        at jess.Agenda.run(Agenda.java:243)
        at jess.Agenda.runUntilHalt(Agenda.java:225)
        at jess.Rete.runUntilHalt(Rete.java:1889)
        at jess.Rete.runUntilHalt(Rete.java:1884)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at jess.Call.call(Call.java:185)
        at jess.FunctionHolder.call(FunctionHolder.java:35)
        at jess.Funcall.execute(Funcall.java:338)
        at jess.FuncallValue.resolveValue(FuncallValue.java:29)
        at jess.Deffunction.call(Deffunction.java:214)
        at jess.FunctionHolder.call(FunctionHolder.java:35)
        at jess.Funcall.execute(Funcall.java:338)
        at jess.Jesp.parseAndExecuteFuncall(Jesp.java:2309)
        at jess.Jesp.parseExpression(Jesp.java:459)
        at jess.Jesp.promptAndParseOneExpression(Jesp.java:309)
        at jess.Jesp.parse(Jesp.java:288)
        at jess.Rete.eval(Rete.java:2583)
        at jess.Rete.eval(Rete.java:2538)
        at jesskb.JessKB.cmd(JessKB.java:108)
        at Beans.UntilHalt$1.run(UntilHalt.java:22)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.IllegalAccessException: Class jess.SerializablePD
can not access a member of class platformcoverage.Track with modifiers
"public"
        at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65)
        at java.lang.reflect.Method.invoke(Method.java:588)
        at jess.SerializablePD.getPropertyValue(SerializablePD.java:51)
        at jess.DefinstanceList.getSlotValueFromObject(DefinstanceList.java:317)
        ... 34 more


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[Ernest Friedman-Hill]

On Jun 17, 2009, at 7:48 AM, Jan Willem Lokin wrote:

> Jess throws an error at me that I don't really understand. The error
> trace as attached. My code used to work earlier, but this has happened
> when I pulled up some common code from two related "...Track" classes
> into a common "Track" superclass. What confuses me most is that the
> IAE message specifically complains about '...modifiers "public"'. A
> quick Google search and some guessing led me to conclude that Jess
> requires that the superclass should have "public" rather than default
> visibility. That makes sense, but it would be nice if it said so.

Java's rules for accessibility via reflection in cases like this  
actually don't make much sense. That said, Jess understands and works  
around them to the extent possible. It sounds like you might have  
found a novel arrangement that's not being handled correctly; can you  
share the source for the base class and one of its children with me?  
(You can send it to me directly at ejfried@... ).


> ---------------------------------------------------------

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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