JNI 101

Question

While you people are connecting universes, I am having a problem running the first JNI program.
invoking JVM from C++;
Started just yesterday and this is very urgent.
The following basic code returns error -3
Also tried running code from sun website, they give me error -1
Cannot create JVM.
since its pretty urgent and I am really short on time, I dont have time to do my research so please give your suggestions and dont get mad!
Appreciatively,
Pranav
#include "jni.h"
#include <iostream.h>
void main() {
JavaVM jvm;       / denotes a Java VM */
JNIEnv env;       / pointer to native method interface */
JavaVMInitArgs vm_args; /* VM initialization arguments */
JNI_GetDefaultJavaVMInitArgs(&vm_args);
jint ret;
ret = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);
if (ret < 0) {
cout << "Can't create JVM! Error: " << ret << endl;
jclass cls = env->FindClass("Prog");
jmethodID mid = env->GetStaticMethodID(cls, "main", "(I)V");
env->CallStaticVoidMethod(cls, mid, 100);
jvm->DestroyJavaVM();

Answer 1

try this one:
//----------------------c-part----------------------------
#include "jni.h" //jvm.lib
#include <string>
#include <iostream>
#include <stdlib.h>
int main()
     const int numberofargs=1;
JavaVMInitArgs vm_args;
JavaVMOption options[numberofargs];
JNIEnv *env=NULL;
JavaVM *jvm=NULL;
     std::string tmpstr="-Djava.class.path=.;";
     options[0].optionString=(char * )tmpstr.c_str();
     vm_args.version=JNI_VERSION_1_4;
vm_args.options=options;
vm_args.nOptions=numberofargs;
vm_args.ignoreUnrecognized=JNI_TRUE;
     if((jint)JNI_CreateJavaVM(&jvm,(void**)&env,&vm_args)<0)
std::cerr << "ERROR:Java Virtual Machine NOT initialized!" << std::endl;
          exit(-1);
     jclass cls;
     if((cls = (jclass)env->FindClass("Hello"))==NULL)
std::cerr << "ERROR:class not found!" << std::endl;
          exit(-1);
     jmethodID mid;
     if((mid=(jmethodID)env->GetStaticMethodID(cls,"main","([Ljava/lang/String;)V"))==NULL)
std::cerr << "ERROR:constructor-method not found!" << std::endl;
          exit(-1);
     jint length=100;
     jint i=0;
     jobject valueobj;
     jclass valuecls;
     jmethodID valuemid;
     jstring jstr;
     jobjectArray valuejoa;
     valuecls=(jclass)env->FindClass("Ljava/lang/String;");
     valuemid=env->GetMethodID(valuecls,"<init>","(Ljava/lang/String;)V");
     valuejoa= env->NewObjectArray(length,valuecls,NULL);
     char buffer[20];
     for(i=0;i<length;i++)
          _itoa( i, buffer, 10 );
          jstr=env->NewStringUTF(buffer);
          valueobj=env->NewObject(valuecls,valuemid,jstr);
          env->SetObjectArrayElement(valuejoa,i,valueobj);
     env->CallStaticVoidMethod(cls, mid, valuejoa);
     jvm->DestroyJavaVM();     
     return 0;
//----------------------java-part--------------------------
public class Hello
     public Hello()
     public static void main(String[] args)
          System.out.println("Hello World:");
          for(int i=0;i<args.length;i++)
               System.out.println(args);
the method "main" get strings, not integers.
jens