Question

I want to call a C subroutine from Java. I’m using JNI. I have created the .java, .c, and .h files, and compiled a DLL. All the files are in the same folder. But when I run the program, it shows an unsatisfiedlinkError. Where am I going wrong…?

As I am learning JNI, the source code I used is the one from: http://www.ibm.com/developerworks/java/tutorials/j-jni/section2.html and things I have already tried:

• Create a dll using Code::Blocks(ide) and GCC as the compiler
• Create dll using GCC from command line (Ref. http://sig9.com/node/35 )
• I am using Win7 32 bit, and I guess all the methods above generate 32-bit DLLs
• All the solutions I found for creating a DLL (shared library) are for MS VC/VCPP and I don’t have that on my machine right now.

Where is the problem? DLL files are being generated without any exception, but when I run the Java code, it throws the exception.

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PS: If there is any theoretical examples that explains how JNI works and what actually it does, then kindly share the link…

The message or exception being thrown:

    c:\myjava1>java Sample1
    Exception in thread "main" java.lang.UnsatisfiedLinkError: Sample1.intMethod(I)I
      at Sample1.intMethod(Native Method)
      at Sample1.main(Sample1.java:11)

At the end of the day after creating dll file lots of times,I am pretty sure that there is possibly no issue with it ,something is wrong with the path …I have changed the loadlibrary method with load method ,but still no luck,…..

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as suggested by a MOD:
I have been discussing about this question on the post:JNI error while calling a C subroutine ,I am posting all the codes here as the comments have limited characters… Sample1.c

#include "jni.h"
#include"Sample_Sample1.h"
JNIEXPORT jint JNICALL Java_Sample_Sample1_test(JNIEnv *env, jobject obj){
return(1);
}
void main(){}

Sample1.java

package Sample;

public class Sample1
{
public native int test();
static{ 
System.loadLibrary("Sample1");
}
public static void main(String[] args)
{
 Sample1 sample = new Sample1();
 System.out.println(sample.test());
 }
}

Sample_Sample1.h(generated using javah -jni command)

/* DO NOT EDIT THIS FILE - it is machine generated */
#include "jni.h"
/* Header for class Sample_Sample1 */

#ifndef _Included_Sample_Sample1
#define _Included_Sample_Sample1
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     Sample_Sample1
 * Method:    test
 * Signature: ()I
 */
JNIEXPORT jint JNICALL Java_Sample_Sample1_test
  (JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

Can anyone guide me where the issue is?In earlier post I mentioned that the code I am using is the one from tutorials ,but to simplyfy the things I have changed the codes …While using **java Sample.Sample1″ i am getting:

c:\myjava1>java Sample.Sample1
Exception in thread “main” java.lang.UnsatisfiedLinkError: Sample.Sample1.test()I
at Sample.Sample1.test(Native Method)
at Sample.Sample1.main(Sample1.java:12)

Answer 1

You need to have your library explicitly set on your path.

It may be the case that the flags you are using there aren’t quite right. Try this:

gcc -Wall -D_JNI_IMPLEMENTATION_ -Wl,--kill-at \
    -I[Java_HOME]/include -I[Java_HOME]/include/win32 \
    -shared -o Sample1.dll Sample1.c

From MinGW GCC site.