how to fix unsatisfiedLinkError when generating dll for JNI in windows platform using g++ - windows

Question

I'm new to native programming. I've been trying to fix the unsatisfiedLinkError past 8-9 hours but got no result. After a lot of googling and stackoverflowing, I got sick of fixing it, I'm posting my problem here. Somebody please please help me.
I'm using g++ compiler in windows 32bit environment.
Here are the files that I've created:
Demo.java
class Demo
{
// Declaration of the native method
public native int methodOfC(int arg1);
/*The native keyword tells the compiler that the implementation of this method is in a native language*/
/*Loading the library containing the implementation of the native method*/
static
{
System.out.println("Control is in Java.......going to call a C program......\n");
System.loadLibrary("try");
System.out.println("Congr8s no prob in CallApi.....\n");
}
public static void main(String[] args)
{
//invoking the native method
int sendToC,getFrmC;
if(args.length!=0) sendToC=Integer.parseInt(args[0]);
else sendToC=999;
Demo ob1=new Demo();
getFrmC=ob1.methodOfC(sendToC);
System.out.println("This is in Java......\n Got "+ getFrmC +" in return from C.");
}//end main
}//end Demo
Demo.h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class Demo */
#ifndef _Included_Demo
#define _Included_Demo
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: Demo
* Method: methodOfC
* Signature: (I)I
*/
JNIEXPORT jint JNICALL Java_Demo_methodOfC
(JNIEnv *, jobject, jint);
#ifdef __cplusplus
}
#endif
#endif
DemoImp.c
#include <jni.h>
#include "Demo.h"
#include <stdio.h>
//definition of methodOfC()
JNIEXPORT int JNICALL Java_Demo_methodOfC(JNIEnv* exeenv, jobject javaobj, int getFrmJava)
{
printf("This is in the C program\n Got %d from java",getFrmJava);
printf("\n.......Exiting frm C\n");
return getFrmJava+1;
}
Here is how I compiled and run my prog.: screenshot here
C:\native>javac Demo.java
C:\native>javah -jni Demo
C:\native>g++ -c -l"C:\Java\jdk1.6.0_26\include" -l"C:\Java\jdk1.6.0_26\include\win32" DemoImp.c
C:\native>g++ -shared DemoImp.o -o try.dll
C:\native>java Demo 1234
Control is in Java.......going to call a C program......
Congr8s no prob in CallApi.....
Exception in thread "main" java.lang.UnsatisfiedLinkError: Demo.methodOfC(I)I
at Demo.methodOfC(Native Method)
at Demo.main(Demo.java:23)
C:\native>
I've already added "C:\native" in my system path variable.
I've uploaded all my files in mediafire. Here's the link native.zip
If possible please tell me how can I make 64bit version of dll. Thanks in advance.

Answer 1

You have missed out the package name in the DemoImp.c file.
The naming convention for C function is Java_{package_and_classname}_{function_name}(JNI arguments). The dot in package name shall be replaced by underscore.