Re: JESS: Call Jess from C++ via JNI

Hunter,

This is not Jess specific question. JVM simply can not find Java class 
to load.
Can you show snippet of the C++ code that starts jvm and tries to load 
TestJNIJessinvoke?

As for overall design, is C++ requirement? Can you do it all in Java?

Dusan Sormaz

On 9/26/2011 8:51 PM, Hunter McMillen wrote:
> Hello everyone,
>
>  I am working on a project where I am using a C++ framework and API to 
> create a game agent. My agent has to be flexible so it can react 
> to/predict events that occur inside the game environment, Jess has the 
> kind of flexibility that I need for my agent to be good,  but I am 
> having trouble connecting to Jess from C++ and that is where I was 
> hoping someone could help me out.
>
> *What I am doing right now*
> I have a C++ program that starts a Java Virtual Machine and searches 
> for a Java class file name "TestJNIJessInvoke"
>
> Inside of "TestJNIJessInvoke.java" I define a simple function in Jess, 
> and try to call that function then print the result
> import jess.*;
> public class TestJNIJessInvoke
> {
>     public static void main(String[] args) throws JessException
>     {
> Rete r = new Rete();
> r.executeCommand("(deffunction square (?n) (return (* ?n ?n)))");
> Value v = r.executeCommand("(square 3)");
>
> System.out.println(v.intValue(r.getGlobalContext()));
>     }
> }
>
> But when I try to compile and link the C++ file with:
> *cl *
> *   -I"C:\Program Files\Java\jdk1.7.0\include" *
> *   -I"C:\Program Files\Java\jdk1.7.0\include\win32" *
> *   TestJNIJessInvoke.cpp *
> *   -link "C:\Program Files\Java\jdk1.7.0\lib\jvm.lib"*
> *
> *
> I get a class loader exception:
> *Exception in thread "main" java.lang.NoClassDefFoundError: jess/Rete*
> *        at TestJNIJessInvoke.main(TestJNIJessInvoke.java:6)*
> *Caused by: java.lang.ClassNotFoundException: jess.Rete*
> *        at java.net.URLClassLoader$1.run(URLClassLoader.java:366)*
> *        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)*
> *        at java.security.AccessController.doPrivileged(Native Method)*
> *        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)*
> *        at java.lang.ClassLoader.loadClass(ClassLoader.java:423)*
> *        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)*
> *        at java.lang.ClassLoader.loadClass(ClassLoader.java:356)*
> *        ... 1 more*
> *
> *
> Exception in thread "main" java.lang.NoClassDefFoundError: jess/Rete
>         at TestJNIJessInvoke.main(TestJNIJessInvoke.java:6)
> Caused by: java.lang.ClassNotFoundException: jess.Rete
>         at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
>         at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
>         at java.security.AccessController.doPrivileged(Native Method)
>         at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
>         at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
>         at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
>         ... 1 more
>
> *Questions*
>
> 1) Is there some other directory that I am supposed to be including 
> that has the .class files for Jess? Right now all I am including is 
> jess.jar
> 2) Is the general design I have a good idea? or is there a better way 
> to facilitate communication between Jess and C++?
>
>
>
> Thanks,
> Hunter McMillen
>

-- 
***************************************************
* Dusan Sormaz, PhD, Associate Professor
* Ohio University
* Department of Industrial and Systems Engineering
* 284 Stocker Center, Athens, OH 45701-2979
* phone: (740) 593-1545
* fax:   (740) 593-0778
* e-mail: [email protected]
* url: http://oak.cats.ohiou.edu/~sormaz/
***************************************************