Develop Reference

Getting java.lang.UnsatisfiedLinkError at runtime

I'm trying to use JNI to access C++ methods from a Java class. I'm able to compile (both in Eclipse or on command line) my Java class fine, but on executing the class at runtime, I'm getting:
Exception in thread "main" java.lang.UnsatisfiedLinkError: com.domain.services.CallServiceAPIS.createSession()I
at com.domain.services.CallServiceAPIS.createSession(Native Method)
at com.domain.services.CallServiceAPIS.main(CallServiceAPIS.java:18)
Java code is as follows:
package com.domain.services;
public class CallServiceAPIS {
static {
System.loadLibrary("service.client");
}
public native int createSession();
public static void main(String[] args) {
System.out.println(System.getProperty("java.library.path"));
new CallServiceAPIS().createSession();
}
}
I included the printout of the java.library.path just to make sure it's pointing to the correct location of the C++ library - and it is. I also tried setting the LD_LIBRARY_PATH in my Eclipse environment. But neither worked.
Note that the System.loadLibrary call IS working since 1) the code compiles and 2) the error occurs on line 18, which is the new CallServiceAPIs call.
C++ code:
int createSession(const PosServiceInfo info, const SessionArgs& args, Domain::UUID& uuidSession)
{
return int::undefined;
}
Any ideas?

Never mind. I realized that I was using the JNI interface incorrectly. I was thinking you could load an EXISTING C++ library using EXISTING C++ source. But you basically have to rewrite the existing code to make use of the JNI interface.

Using GraphVIZ Native library from Java

I am trying to use graphviz native library from java.I am able to compile the program in Eclipse. But getting exception:
Exception in thread "main" java.lang.UnsatisfiedLinkError: no gv in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1681)
at java.lang.Runtime.loadLibrary0(Runtime.java:840)
at java.lang.System.loadLibrary(System.java:1047)
at org.graphviz.test.Test.<clinit>(Test.java:12)
Could not find the main class: org.graphviz.test.Test. Program will exit.
Here is my code(copied from somewhere of course):
package org.graphviz.test;
import org.graphviz.internal.SWIGTYPE_p_Agedge_t;
import org.graphviz.internal.SWIGTYPE_p_Agnode_t;
import org.graphviz.internal.SWIGTYPE_p_Agraph_t;
import org.graphviz.internal.gv;
public class Test {
static {
System.loadLibrary("gv");
}
public static void main(String[] args) {
SWIGTYPE_p_Agraph_t g, sg;
SWIGTYPE_p_Agnode_t n, m;
SWIGTYPE_p_Agedge_t e;
g = gv.digraph("G");
System.out.println(gv.setv(g,"aaa","xxx"));
System.out.println(gv.getv(g,"aaa"));
sg = gv.graph(g,"SG");
n = gv.node(g,"hello");
System.out.println(gv.getv(n,"label"));
System.out.println(gv.setv(n,"aaa","xxx"));
System.out.println(gv.getv(n,"aaa"));
m = gv.node(g,"world");
System.out.println(gv.getv(m,"aaa"));
e = gv.edge(n,m);
System.out.println(gv.setv(e,"aaa","xxx"));
System.out.println(gv.getv(e,"aaa"));
gv.rm(e);
gv.rm(n);
gv.rm(m);
gv.rm(g);
g = gv.readstring("digraph G {a->b}");
gv.rm(g);
g = gv.read("hello.gv");
gv.layout(g,"dot");
gv.render(g,"png","hello.png");
gv.rm(g);
}
}
I have pointed the library correctly, but at runtime getting UnsatisfiedLinkError. Any one ever tried using the graphviz native library?Please let me know how to configure JNI.

I believe you're problem is that you are trying to import from gv, but you aren't specifying what you want to import. It's kind of like if you were to just write ---
import org.graphviz.internal;
Instead, try importing a specific library from the gv library. For example, if you want a directed graph, you would probably do something like this ---
import org.graphviz.internal.gv.digraph;
Take a look at the following document and see if it helps at all. It might give you a better idea of where gv comes from and how you can import the methods associated with it.
http://www.graphviz.org/pdf/gv.3java.pdf

Get graphviz-java
Make sure you have graphviz-java installed. For MacPorts this should work like this:
sudo port install graphviz +java
This actually failed for me on the first try and complained about swig-java, this fixed it:
sudo port install swig-java
sudo port install graphviz +java
Now the library is installed under /opt/local/lib/graphviz/java for me, search for libgv.jnilib if you don't find it there.
Setup class path
I compiled in Eclipse, for that I added /opt/local/lib/graphviz/java to the build path as an external class folder.
Compile
This is a simple example that writes an image. Note that System.loadLibrary("gv") must happen before calling anything in graphviz.
import org.graphviz.SWIGTYPE_p_Agedge_t;
import org.graphviz.SWIGTYPE_p_Agnode_t;
import org.graphviz.SWIGTYPE_p_Agraph_t;
import org.graphviz.gv;
public class Main {
static {
System.loadLibrary("gv");
}
public static void main(String[] args) {
SWIGTYPE_p_Agraph_t g = gv.digraph("G");
SWIGTYPE_p_Agnode_t n = gv.node(g, "hello");
SWIGTYPE_p_Agnode_t m = gv.node(g, "world");
SWIGTYPE_p_Agedge_t e = gv.edge(n, m);
gv.layout(g, "dot");
gv.render(g, "png", "hello.png");
}
}
Run
Run with java.library.path=/opt/local/lib/graphviz/java, e.g. -Djava.library.path=/opt/local/lib/graphviz/java as VM arguments in an Eclipse run configuration.

OpenCV + Java = UnsatisfiedLinkError

I need capture a video stream from my USB webcam, for this i use Opencv 2.4.6 for developing in Java. I follow the steps listed in here
I add the "C:\opencv\build\java\x64" dir to my System PATH and include the "opencv-246.jar" file into my libraries on ECLIPSE. When y run the explame
import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
public class Main {
public static void main(String[] args) {
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
Mat m = Mat.eye(3, 3, CvType.CV_8UC1);
System.out.println("m = " + m.dump());
}
}
i get
m = [1, 0, 0;
0, 1, 0;
0, 0, 1]
OK =)
but when i run
import org.opencv.highgui.VideoCapture;
public class Main {
public static void main(String[] args) {
VideoCapture vc = new VideoCapture(0);
if(vc.isOpened()){
System.out.println("Works!");
}
}
}
i get
Exception in thread "main" java.lang.UnsatisfiedLinkError: org.opencv.highgui.VideoCapture.n_VideoCapture(I)J
at org.opencv.highgui.VideoCapture.n_VideoCapture(Native Method)
at org.opencv.highgui.VideoCapture.<init>(VideoCapture.java:113)
at Main.main(Main.java:5)
i add all the routes containes in:
C:\opencv\build\x64\vc10
one by one,but doesn`t work.
Finally i create a variable called OPENCV_DIR with C:\opencv\build\x64\vc10 but still getting UnsatisfiedLinkError.
PLEASE HELP ME!

in your second example , you skipped this line
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
so the opencv libs werent loaded, UnsatisfiedLinkError, etc...
[edit]:
thanks to #Jishnu Prathap for highlighting the java.library path issue, if you run into problems setting that, you can still try to use an absolute path to the java wrapper so/dll/dylib like:
System.load("/path to/our/java_wrapper");

I had a similar error while using OpenCV with java.I did 2 things to resolve it.
static{ System.loadLibrary(Core.NATIVE_LIBRARY_NAME); }
I added the path to OpenCV dll or .so to javalibpath or path. which actually didnt work for some reason and i ended up putting the OpenCV dll in the system32 folder.

Try the below code
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import nu.pattern.OpenCV;
public class OpencvMain
{
public static void main( String[] args )
{
OpenCV.loadLocally();
Mat mat = Mat.eye( 3, 3, CvType.CV_8UC1 );
System.out.println( "mat = " + mat.dump() );
}
}

For general users using opencv3.x:
HighGUI module does not exist anymore in Java for opencv 3.0 and above.
import org.opencv.videoio.VideoCapture;
instead of
import org.opencv.highgui.VideoCapture;
videoio includes VideoCapture, VideoWriter.
Similarly:
imgcodecs includes imread/imwrite and friends
Example:
Highgui.imread(fileName)
-->
Imgcodecs.imread(fileName)

So, I was having this problem too and I did what you all suggested, it worked fine in my x64 windows, but in a x86 couldn't make it work.
At last I found a solution by changing:
VideoCapture capture = new VideoCapture(0);
for
VideoCapture capture = new VideoCapture();
capture.open("resources/vid.MP4");
I don't know why this worked but I hope it may help somebody with my same problem.

I tried a lot of tutorials online for the resolution, only one of them have helped me.
There are two steps that are different in this method,
Firstly, while importing the java project from Opencv SDK into the Android studio, make sure to uncheck all the checkboxes presented in the import dialog.
Secondly, make sure you import the OpenCV.mk file that is in the native/jdk of the SDK..
The System.loadLibrary() seems to return true after this, which was a huge relief for me as it took me several hours to figure this out
Here's the link to the tutorial that helped me
https://medium.com/#rdeep/android-opencv-integration-without-opencv-manager-c259ef14e73b

Opening a TCL gui within Java code

I have a TCL file which uses Tcl's BWidget package that I've been using as a GUI for my program. I now want to be able to load up this GUI from a separate Java program. I've looked into Jacl and Swank, but they don't seem to do exactly what I want.
I've tried the following with Jacl but it's unable to evaluate the file. While debugging, I can see that it completes parsing my tcl file, but it throws an exception while parsing through the BWidget package tcl files. Here's my Java code:
Interp interp = new Interp();
try {
interp.evalFile("C:\\CTP\\Tcl\\LuxonCtp32.tcl");
} catch (TclException ex) {
int code = ex.getCompletionCode();
System.err.println("command returned bad error code: " + code);
} finally {
interp.dispose();
}
Any ideas on how I can accomplish what I want to do? Is it even possible?

Tcl itself can not display a GUI. It uses a plugin called Tk for that.
In the C reference implementation of Tcl you get Tk as well.
Tk has not been ported to Java, Tcl has.
You can not use Jacl to display Tk widgets, but TclBlend could do that, because TclBlend uses the C reference implementation of Tcl. That means that the user needs a working Tcl/Tk installation.
There are some problems with TclBlend and Tcl > 8.5 through, which result in a segfault.
IIRC you have to remove the conditional if around Tcl_FindNameOfExecutable in TclBlends C code (and compile it yourself).

Go to this site http://jtcl-project.github.io/jtcl/ and download now for the binary zip. Its a recent java tcl on github called Jtcl.
Unzip it and you will find a jar called jtcl-2.7.0.jar.
I am using Netbeans 8 my preference.
I add the jar into Project Library.
I create a java file called JTclHallo.java and this is the code.
package jtclhallo;
// import tcl.lang it belongs to jtcl-2.7.0 jar a must
import tcl.lang.*;
// Java wrapper to test JACL or JTCL.
public class JTclHallo {
public static void main(String []args) {
//Interp is a java class belonging to tcl.lang. Unrar the jtcl-2.7.0
Interp i = new Interp();
try {
//call your tcl file mine was swing.tcl from the E drive
i.eval("source E:/private/swing.tcl");
} catch (TclException e) {
System.out.println("Exception: " + e.getMessage());
}
}
}
For swing.tcl
package require java
set window [java::new javax.swing.JFrame]
$window setSize 600 400
$window setVisible true

JNA to call a DLL without source code from java

I have to call a dll method and I don't have the source code from dll, I was reading about JNI and understood that you should have the source to input the JNI library in the code (.h).
My second shoot is JNA, but I am getting the same error, although you don't have to change anything in DLL.
I created two classes to test:
interface:
package icom;
import com.sun.jna.Library;
public interface IConectorT extends Library {
int StartConector(byte[] conectorStatus, String icomPath);
}
DLL method call:
package icom;
import com.sun.jna.Native;
public class ConectorTJna {
public static void main(String args[]) {
IConectorT lib = (IConectorT) Native.loadLibrary("ConectorT", IConectorT.class);
int teste = lib.StartConector(null, "C:\\ICOM");
System.out.println("RESULT: " + teste);
}
}
When I call the lib.StartConector method I get this:
Exception in thread "main" java.lang.UnsatisfiedLinkError: Error
looking up function 'StartConector': The specified procedure could not
be found. at com.sun.jna.Function.(Function.java:179) at
com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:350) at
com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:330) at
com.sun.jna.Library$Handler.invoke(Library.java:203) at
$Proxy0.StartConector(Unknown Source) at
icom.ConectorTJna.main(ConectorTJna.java:10)

Did you specify path to the library, e.g. using system property?
Here are the details from "Getting Started with JNA" guide:
Make your target library available to your Java program. There are two
ways to do this:
The preferred method is to set the jna.library.path system property to
the path to your target library. This property is similar to
java.library.path, but only applies to libraries loaded by JNA.
Change the appropriate library access environment variable before launching
the VM. This is PATH on Windows, LD_LIBRARY_PATH on Linux, and
DYLD_LIBRARY_PATH on OSX.
Taken from: https://github.com/twall/jna/blob/master/www/GettingStarted.md