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Adding native library to java project results with unsatisfied link

I am constantly running into error when i try to add .dll to build path of java project.
I have created .dll file with mingw64 using the following command:
gcc -o ctest.dll -shared -I"C:\Program Files\Java\jdk1.8.0_45\include"
-I"C:\Program Files\Java\jdk1.8.0_45\include\win32" ctest.c -LC -m64
Created .dll file is in the same directory as the main class using the dll.
bin/com/jni
I have tried to include .ddl to java project from Eclipse by doing the following steps:
BuildPath -> Native library location -> path_to_directory_with_.dll
This results with:
Exception in thread "main" java.lang.UnsatisfiedLinkError: com.jni.HelloWorld.helloFromC()V
at com.jni.HelloWorld.helloFromC(Native Method)
at com.jni.HelloWorld.main(HelloWorld.java:14)
As the above didn't work, i tried to run the application from command line:
C:\Users\Z003DP9F\java-8 workspace\workspace\JNI_Test\bin>java
-Djava.library.path="C:\Users\Z003DP9F\java-8 workspace\workspace\JNI_Test\bin\com\jni"
com.jni.HelloWorld
and the same error, although on line 12 rather than 14 like in example above.
Exception in thread "main" java.lang.UnsatisfiedLinkError: com.jni.HelloWorld.helloFromC()V
at com.jni.HelloWorld.helloFromC(Native Method)
at com.jni.HelloWorld.main(HelloWorld.java:12)
c file:
#include <jni.h>
#include <stdio.h>
JNIEXPORT void JNICALL Java_HelloWorld_helloFromC
(JNIEnv * env, jobject jobj)
{
printf("Hello from C!\n");
}
Java main class:
package com.jni;
public class HelloWorld {
native void helloFromC(); /* (1) */
static {
System.loadLibrary("ctest"); /* (2) */
}
static public void main(String argv[]) {
HelloWorld helloWorld = new HelloWorld();
helloWorld.helloFromC(); /* (3) */
}
}
The example i have been trying to setup was taken form:
jni

The signature is wrong; you can use javah to get the signature for you, but in your case it is simply
JNIEXPORT void JNICALL Java_com_jni_HelloWorld_helloFromC(JNIEnv * env, jobject thiz)

JNI UnsatisfiedLinkError without wrong method names and with library path specified

I'm trying to work build my very first JNI application, following this tutorial: https://www3.ntu.edu.sg/home/ehchua/programming/java/JavaNativeInterface.html
Problem Summary: While running my application, I get an java.lang.UnsatisfiedLinkError error.
First I wrote the Class HelloJNI.java:
public class HelloJNI {
static {
System.loadLibrary("hello"); // Load native library at runtime
// hello.dll (Windows) or libhello.so (Unixes)
}
// Declare a native method sayHello() that receives nothing and returns void
private native void sayHello();
// Test Driver
public static void main(String[] args) {
new HelloJNI().sayHello(); // invoke the native method
}
}
This class I compiled with:
javac HelloJNI.java
Next I ran javah HelloJNI
This produced the following file HelloJNI.h:
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class HelloJNI */
#ifndef _Included_HelloJNI
#define _Included_HelloJNI
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: HelloJNI
* Method: sayHello
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_HelloJNI_sayHello
(JNIEnv *, jobject);
#ifdef __cplusplus
}
#endif
#endif
Next I implemented HelloJNI.c:
#include <jni.h>
#include <stdio.h>
#include "HelloJNI.h"
// Implementation of native method sayHello() of HelloJNI class
JNIEXPORT void JNICALL Java_HelloJNI_sayHello(JNIEnv *env, jobject thisObj) {
printf("Hello World!\n");
return;
}
Finally I compiled the c class:
gcc -I"/usr/lib/jvm/java-8-oracle/include" -I"/usr/lib/jvm/java-8-oracle/include/linux" -c -Wall -Werror -fpic HelloJNI.c
gcc -shared -o hello.so HelloJNI.o
This produces the files hello.so and HelloJNI.o. Next I try to run the code:
java -Djava.library.path=. HelloJNI
This produces the error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: no hello in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1864)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at HelloJNI.(HelloJNI.java:3)
This seems to be the most common JNI error on the internet... My method names seem to be correct. I also ran:
nm hello.so | grep say
This gives me: 00000000000006b0 T Java_HelloJNI_sayHello which seems to be correct, i.e. the compiler didn't add additional characters. I simply ran out of ideas of things I could try. Any suggestions?
My OS: Linux Mint 13, GCC version 4.7.3, java version 1.8.0_60
==========UPDATE===============
When I replace System.loadLibrary("hello"); by System.load("/usr0/home/jkinable/workspace/javaIDEA/jnitest/hello.so"); my HelloWorld example works! However, I don't want to use an absolute path so I'm still looking for a way to use System.loadLibrary("hello"); instead? Any suggestions? I've also tried running on a different linux system, but I get the same issue.

It turns out that the problem is due to some naming convention on unix/linux platforms! When using:
System.loadLibrary("hello");
the file should not be named hello.so! Instead, the name should be libhello.so. On Windows, use hello.dll. I'm surprised that this issue is not mentioned in IBM's JNI tutorial: http://www.ibm.com/developerworks/java/tutorials/j-jni/j-jni.html
I'm not sure what the rationality behind this issue is. Why would you load a library "hello" which should be named libhello.so on your filesystem (instead of hello.so)?

How to solve "fatal: relocations remain against allocatable but non-writable sections" while using Java native interface?

I'm trying to call a C function inside a Java code.
I have this hava code.
public class JavaToC {
public native void helloC();
static {
System.loadLibrary("HelloWorld");
}
public static void main(String[] args) {
new JavaToC().helloC();
}
}
. I compiled it and then created header file. Then make the following HelloWorld.c file.
#include <stdio.h>
#include <jni.h>
#include "JavaToC.h"
JNIEXPORT void JNICALL Java_JavaToC_helloC(JNIEnv *env, jobject javaobj)
{
printf("Hello World: From C");
return;
}
I tried compiling this using "gcc -o libHelloWorld.so -shared -I/usr/java/include -I/usr/java/include/solaris HelloWorld.c -lc", but it gives the following result.
Text relocation remains referenced
against symbol offset in file
.rodata (section) 0x9 /var/tmp//cc.GaGrd.o
printf 0xe /var/tmp//cc.GaGrd.o
ld: fatal: relocations remain against allocatable but non-writable sections
collect2: ld returned 1 exit status
I'm working on Solaris 11, how can I solve this?

I cannot test this on a Solaris machine at the moment, but from http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/SPARC-Options.html
-mimpure-text suppresses the “relocations remain against allocatable but non-writable sections” linker error message. However, the
necessary relocations will trigger copy-on-write, and the shared
object is not actually shared across processes. Instead of using
-mimpure-text, you should compile all source code with -fpic or -fPIC.
the solution seems to be to add the -fpic option to generate position-independent code.

Java: Invoking native method giving "Exception in thread "main" java.lang.UnsatisfiedLinkError"

I am trying to call a simple native method in Java from C++, to achieve this I do the following:
Create a simple class as shown below:
public class HelloNative{
public native void printString(String str);
static{
System.out.println("Current Directory is: " + System.getProperty("user.dir"));
System.load(System.getProperty("user.dir") + "/libhellonative.so");
}
public static void main(String[] args){
System.out.println("Calling Native Libraray (libhellonative.so) method printString");
new HelloNative().printString("Message from Java to C");
}
}
Create .h file for the native method using javah -jni which create the following declaration:
JNIEXPORT void JNICALL Java_HelloNative_printString(JNIEnv *, jobject, jstring);
Implement the native function in .cpp file as:
JNIEXPORT void JNICALL Java_HelloNative_printString(JNIEnv* jni_env, jobject java_obj, jstring msg){
printf("inside native method\n");
jboolean iscopy;
const char *message = (jni_env)->GetStringUTFChars( msg, &iscopy);
printf("%s", message);
}
And finally create the .so file using:
g++ HelloNative.cpp -o libhellonative.so -shared -Wl,-soname,libhellonative.so -static -lc -I /usr/lib/jvm/java-6-sun-1.6.0.26/include -I /usr/lib/jvm/java-6-sun-1.6.0.26/include/linux
But when I compile and run the .java file it's giving me Runtime Exception:
Current Directory is: /home/gmuhammad/Projects/test
Calling Native Libraray (libhellonative.so) method printString
Exception in thread "main" java.lang.UnsatisfiedLinkError: HelloNative.printString(Ljava/lang/String;)V
at HelloNative.printString(Native Method)
at HelloNative.main(HelloNative.java:16)

Ok, I got this to work. It has nothing to do with loading the library, but with actually calling the method from that library.
I created .java, .h and .cpp files by copy/paste from your question and ran them (I had to add #include <jni.h> in the .cpp file) - and got exactly the same error as you did.
Then I edited the .cpp file to include the generated .h file. Also, as maba indicated in his answer, you need to call (jni_env)->ReleaseStringUTFChars(msg, message); to release the object. My full .cpp file now looks like this:
#include "HelloNative.h"
JNIEXPORT void JNICALL Java_HelloNative_printString(JNIEnv* jni_env, jobject java_obj, jstring msg){
printf("inside native method\n");
jboolean iscopy;
const char *message = (jni_env)->GetStringUTFChars( msg, &iscopy);
printf("%s", message);
(jni_env)->ReleaseStringUTFChars(msg, message);
}
I re-compiled the library, ran the java code - and voila! everything works. This way, it works regardless of which way you load the library, with load or loadLibrary.
Give it a try.

I recommend to load the library slightly differently.
Place your libmynative.so into whatever directory you like.
Add that directory to LD_LIBRARY_PATH variable.
In your java code, change System.load call to be System.loadLibrary("mynative") (note the lack of full path, prefix lib and extension .so)
Run your java code.
Have a look here for more details: http://java.sun.com/developer/onlineTraining/Programming/JDCBook/jniexamp.html

It is totally OK to use the System.load() but you will have to be sure that your shared libraries really are where you say they should be.
Current Directory is: /home/gmuhammad/Projects/test
Your code is trying to access the shared library in that directory. Are you sure that the libhellonative.so is there?
Then you can also use the System.mapLibraryName("hellonative") to get the name of the shared library for the current platform. That makes it more platform independent. The call will give you libhellonative.so on linux and hellonative.dll on windows.
Also you must call (jni_env)->GetReleaseUTFChars(msg, message); to release the objects.

JNI error while calling a C subroutine

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.
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,.....
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)

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.

Have you checked your DLL by calling it from a stub C++ application? Pay particular attention to the exact name (including capitalisation) of the method(s) you are calling.
The Javadoc for UnsatisfiedLinkError says "Thrown if the Java Virtual Machine cannot find an appropriate native-language definition of a method declared native." That probably means either that the name is misspelled or your DLL is not where the JVM is expecting to find it.

Finally solved the problem using System.load() method, System.loadLibrary() Still doesn't work for me...it keeps on giving the same exception, And the I think the issue was with the .dll Thanks to all of you who supported and responded...

After spending 2hrs and analysing the code. Problem is with .dll/.so compilation. Below command works for me:
g++ -dynamiclib HelloJni.cpp -I /usr/include/ -I /usr/lib/jvm/java-1.8.0-openjdk-amd64/include/ -I /usr/lib/jvm/java-1.8.0-openjdk-amd64/include/linux/ -shared -o libHelloJni.so
or
g++ -dynamiclib HelloJni.cpp -I /usr/include/ -I $JAVA_HOME/include/ -I $JAVA_HOME/include/linux/ -shared -o libHelloJni.so
Above command is for linux. In case of Windows, change
[Java_HOME]/include/linux/ ---> [Java_HOME]/include/win/
Mac:
$Java_HOME/include/linux/ ---> $Java_HOME/include/darwin/