This is all perfectly reasonable so far. When you create the JVM you'll need to tell it where jess.jar is, along with any other jars you use, with the "-cp" flag or the "java.class.path" property.
Once you have this working, you'll presumably want to connect things a little more tightly. You can use the JNI API to write the equivalent of your three-line main() in C++ pretty easily; you'll want to put together a C++ version "executeCommand()" that controls the Rete instance, passes a script along, executes it, and gets the Value back, decoding it as needed. ________________________________ From: owner-jess-us...@sandia.gov [mailto:owner-jess-us...@sandia.gov] On Behalf Of Hunter McMillen Sent: Monday, September 26, 2011 8:51 PM To: jess-users Subject: JESS: Call Jess from C++ via JNI 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
