Class.forName problem

Question

Hi,
I'm using "Java Invocation API" to load a class and call a generic method of it,
but the "forName" call fails with error:
     Exception in thread "Thread-4" java.lang.ClassNotFoundException: HelloWorld
          at java.lang.Class.forName0(Native Method)
          at java.lang.Class.forName(Class.java:217)
here is my (pseudo) code:
// connect to my class "HelloWorld"
myClass = (*envP)->FindClass(env, "HelloWorld")
// connect to class "Java/lang/Class"
classClass = (*env)->FindClass(env, "java/lang/Class")
// get the id of Class.forName method
forNameID = (*env)->GetStaticMethodID(env, classClass, "forName", "(Ljava/lang/String;)Ljava/lang/Class;")
// j name of HelloWorld
jClassName = (*env)->NewStringUTF(env, "HelloWorld")
// call forName -> fails
jClassObject = (*env)->CallStaticObjectMethod(env, classClass, forNameID, jClassName)
     -----> Exception in thread "Thread-4" java.lang.ClassNotFoundException: HelloWorld
          at java.lang.Class.forName0(Native Method)
          at java.lang.Class.forName(Class.java:217)
Sustem: MacOSX 10.2.8
Java Version: 1.4.1
$CLASSPATH env var: /System/Library/Frameworks/JavaVM.framework/Versions/1.4.1/Classes
Can somebody help me or point me to some useful URL about this?
Thanks

Answer 1

Here is a simple app that demonstrates my problem. I compiled and ran it on MacOSX but I have the same problem on windows. Copy the following code in a file named "javatest.c", cd to that directory and compile it with commad:
gcc -o javatest javatest.c -framework JavaVMthen run it with:
./javatestCode:
#include <JavaVM/jni.h>
//===========================================================================================
static void print_exception(JNIEnv *envP)
     // output the exception
     if (envP && ((*envP)->ExceptionOccurred(envP) != NULL))
     {     (*envP)->ExceptionDescribe(envP);
          (*envP)->ExceptionClear(envP);
//===========================================================================================
int main()
JavaVMInitArgs     vm_args;
JavaVM               *jvm;
JavaVMOption        options[5];
char               *classPathEnv;
char               *classPathString;
jint               res;
JNIEnv                *envP = NULL;
jclass               jlcClass;
jmethodID          forNameID;
jstring               jClassName;
jobject               jClassObject;
     vm_args.version = JNI_VERSION_1_2;
     // options
     vm_args.nOptions = 5;
     options[0].optionString = "-verbose:class" ;
     options[1].optionString = "-verbose:jni" ;
     options[2].optionString = "-verbose:gc" ;
     classPathEnv = (char *)getenv( "CLASSPATH" );
     if (!(classPathString = (char*)malloc(strlen( "-Djava.class.path=" ) + strlen(classPathEnv) + 1)))
printf("malloc failed\n");
          exit(1);
     sprintf(classPathString, "%s%s" ,"-Djava.class.path=" , classPathEnv);
     options[3].optionString = classPathString;
     options[4].optionString = "vfprintf" ;
     options[4].extraInfo = vfprintf;
     vm_args.options = options;
     vm_args.ignoreUnrecognized = JNI_FALSE;
     // Load the jvm
     res = JNI_CreateJavaVM(&jvm, (void**)&envP, &vm_args);
     if (res != JNI_OK)
     {     printf("CreateJavaVM failed\n");
          exit(1);
     // find the class "java/lang/Class"
     if (!(jlcClass = (*envP)->FindClass(envP, "java/lang/Class")))
     {     printf("FindClass java/lang/Class failed\n");
          print_exception(envP);
          exit(1);
     // find the method ID of Class.forName
     if (!(forNameID = (*envP)->GetStaticMethodID(envP, jlcClass, "forName", "(Ljava/lang/String;)Ljava/lang/Class;")))
     {     printf("GetStaticMethodID forName failed\n");
          print_exception(envP);
          exit(1);
     // make a java string of my "HelloWorld" class
     if (!(jClassName = (*envP)->NewStringUTF(envP, "HelloWorld")))
     {     printf("NewStringUTF failed\n");
          print_exception(envP);
          exit(1);
     // call method Class.forName
     if (!(jClassObject = (*envP)->CallStaticObjectMethod(envP, jlcClass, forNameID, jClassName)))
     {     printf("CallStaticObjectMethod of forName failed\n");
          print_exception(envP);
          exit(1);
     // fail with:
     // java.lang.ClassNotFoundException: HelloWorld
     //        at java.lang.Class.forName0(Native Method)
     //        at java.lang.Class.forName(Class.java:115)
return 0;
}HelloWorld java code (compiled in a .class file located in $CLASSPATH folder):
public class HelloWorld
     public static void main (String args[]) throws Exception
          System.out.println ("HelloWorld");
}Someone can help me about this?