CODEWITHSUNDEEP
javac++global-variablesjna.so
Charles Socié
Charles Socié

Reputation: 23

load lib .so with jna

I am actually trying to open a library. So (I did it in c++) with JNA my problem is that I can not open a library when there is a static variable. However I have to use un singleton in my library so I am looking for why a static variable can not be use with JNA to prove it a made a little library

there is the .h file:

#ifndef UNTITLED1_LIBRARY_H
#define UNTITLED1_LIBRARY_H
#include <iostream>
class library {
 private:
  static char* h;
 public:
  int hello();
};

extern "C" int hello(){
 library lib;
 return lib.hello();
}

#endif

then my .cpp file:

#include "library.h"
#include "ecrire.h"

#include <iostream>

int library::hello() {
 h = (char*)"hello world";
 std::cout<<h<<std::endl;
 return 45;
}

then my java class and interface

public class Westgard {
static {       
    System.setProperty("jna.library.path","../logic/resources/calculator"); 
}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    int maj = InterfaceLibWestgard.INSTANCE.hello();
    System.out.println(maj);
}

}


import com.sun.jna.Library;
import com.sun.jna.Native;

public interface InterfaceLibWestgard extends Library {
  int hello();
  static InterfaceLibWestgard INSTANCE = (InterfaceLibWestgard) 
  Native.loadLibrary("../logic/resources/calculator/libuntitled1.so", 
  InterfaceLibWestgard.class);
}

So if I try like this it wont work but when a remove the static from the .h it works does not anyone know why I have been looking for since 4-5 hours still do not know why...

This is my issue log:

Exception in thread "main" java.lang.UnsatisfiedLinkError: Unable to load 
 library '../logic/resources/calculator/libuntitled1.so': Native library 
(linux-x86-64/../logic/resources/calculator/libuntitled1.so) not found in 
resource path ([file:/opt/java/jdk1.8.0_151/jre/lib/resources.jar,

Upvotes: 2

Views: 2584

Answers (2)

Primesh
Primesh

Reputation: 67

You could use Native.load() instead of Native.loadLibrary().

Check the code below,

    public interface MyLibrary extends Library {
        int myMethod();
    }

    static {
        MyLibrary lib = (MyLibrary)Native.load("untitled1" , MyLibrary.class);
    }

You can add the file in the resource location and load it in the above manner easily. You should exclude the "lib" prefix and ".so" file type. In your case,

filename = "untitled1"

Using JNA to Access Native Dynamic Libraries

Upvotes: 1

Alan Birtles
Alan Birtles

Reputation: 36603

You have declared library::h but not defined it. You need to add

char* library::h = 0;

in your cpp file.

Presumably the library is either failing to compile or it is compiling but expecting this missing symbol to be defined in another library.

Upvotes: 1

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