I have been trying to use OpenCV with Java without success. I am currently running Linux. I downloaded the OpenCV library from Github, but when I try to run any program, it gives me an error on the line: System.load(Core.NATIVE_LIBRARY_NAME);
The error is "Exception in thread "main" java.lang.UnsatisfiedLinkError: Expecting an absolute path of the library: opencv_java400"
I have been told I need to provide a path to a .dll file; however, the current version of OpenCV appears not to contain any .dll files.
Any suggestions would be appreciated, thank you.
The message of the Exception is everything you need. You are supposed to provide an absolute path to the file.
Normally you would put the native libraries as resource in your java package (*.jar). Before loading you must extract the file to a temporary directory of the executing system and then invoke the System.load(..).
As already mentioned a dll typically names a dynamic runtime library on windows os.
Related
I am having an issue when loading a dll file using java. I am getting
java.lang.UnsatisfiedLinkError: Unable to load library 'C:\Users\GZammit\Documents\gapt\RwLibraries': Native library (win32-x86-64/C:\Users\GZammit\Documents\gapt\RwLibraries.dll) not found in resource path ...
This is my code :
ClassApi INSTANCE = (ClassApi) Native.loadLibrary(System.getProperty("user.dir")+"\\RwLibraries\\renderwarriors", ClassApi.class);
I did a lot of research and I know there are many with same error but none of the solutions worked for me. The weird thing is, it shows you which files it searched and one of the files is the actual path of the dll location. I even printed out both urls to confirm. I also placed the dll in many other location including the sysWOW64.
I also changed the java.library.path before loading the dll to make sure it is in that particular path without success either. I also followed multiple tutorials online doing exactly the same code without success.
I am using jna 4.4.0 jar file and jna-platform 4.4.0 . I checked the java path and also placed a dll in one of the paths mentioned.
There should be no error code-wise since it worked for my team but not on my computer. I also tried on two different computers.
Everything is 64-bit including the dll.
I am trying to run a program which uses JMagick. I have added the native library libJMagick.so as well as libMagick.so.10 (64 bit, matching my system's architecture) to my java.library.path. But when I am trying to run the program I am getting following error:
libJMagick.so: libMagick.so.10: cannot open shared object file: No
such file or directory
From error, it looks like it is finding the libJMagick.so file, but it is not able to find libMagick.so.10, although it is present in java.library.path.
I have ImageMagick installed in my system.
When you copy the .so files, Please do it in respective folders. So that the Java application will load the libraries available for the usage. This is all about your configuration issue. Where to store the shared object files, They should be available on the path.
I'm using Windows 7 and getting this exception when trying to run a Java project that uses opencv libraries:
Exception in thread "main"
java.lang.UnsatisfiedLinkError: no opencv_java in java.library.path
at java.lang.ClassLoader.loadLibrary(Unknown Source)
at java.lang.Runtime.loadLibrary0(Unknown Source)
at java.lang.System.loadLibrary(Unknown Source)
at org.opencv.highgui.Highgui.<clinit>(Highgui.java:416)
at teste.main(teste.java:21)
What did I do wrong? Is some import missing?
I want to create a simple Java project in Eclipse (not Android), that uses openCV.
So I've extracted javacv from OpenCV-2.4.2.exe file to C:\
Then executed "cmake -G "MinGW Makefiles" -DBUILD_opencv_java=ON
C:\opencv" command and after that, "mingw32-make". Everything was
build without errors or warnings
After I've added opencv dll's to my Environment Variables
This exception is raised because the system is trying to find native libraries that OpenCV needs for this specific platform, and does not find them.
Exception in thread "main"
java.lang.UnsatisfiedLinkError: no opencv_java in java.
To solve this error:
If you are using opencv version < opencv 2.4.6 then the answer given by #user3033420 is the solution.
If you are using version >= opencv 2.4.6, then the jar has a constant variable in Core class named NATIVE_LIBRARY_NAME that you give to the loadLibrary() function in FaceDetector class to include features of opencv in your project, you probably already have this:
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
Using the above named constant, there is no need to remember name of strang dll files.
Add the opencv 2.4.9.jar to the build path from project preferences as:
Window -> Preferences -> Java Build Path –> Add Library -> User Libraries ->
User Library -> & click New
You will see a dialog as below. Add opencv-2.4.9 as Library Name & click Ok.
Then Add External Jar & locate your opencv jar & click ok. Then expand opencv-2.4.9.jar & click on Native Library Location (None) as shown below :
Necessary step: enter the location of the folder containing native library used by "opencv-2.4.9" & then click OK as shown below :
So now the jar now has all the native libraries it needs to do the work. Rebuild the java program and everything should compile and run as designed.
If you get this error:
Exception in thread "main"
java.lang.UnsatisfiedLinkError: no opencv_java in java.library.path
It probably means you are shooting from the hip, programming by brownian motion, trying to get openCV to work. Like trying to figure out how an airplane works in flight by pressing all the buttons furiously. You're going to have a bad time.
What the error means:
Eclipse is telling you that the jar file can't find libraries it needs to do its job. So naturally it's not going to work until you make them available. You've got to find a tutorial on "how to build openCV from source" on your particular platform: (windows, mac, linux, etc), (32bit, 64bit, etc).
Basically, you glossed over the 'Native library location' settings, or didn't set them correctly, and so the jar can't find its support libraries written in C.
How do fix it, thousand foot view:
Download the source code for openCV for your operating system.
Follow the directions to build openCV from source.
Copy the jar into a lib directory in your Java project.
Configure the jar to look for its native libraries by setting the "native library location" to the build/lib directory under the path where you built openCV from source.
Clean build the java project, and the UnsatisfiedLinkError should go away.
This blog talks about the steps above in step-by-step detail: https://udallascs.wordpress.com/2014/03/30/adding-opencv-and-configuring-to-work-with-eclipse-and-java/
Why can't this just be a simple jar?
Because most of openCV is written in the C programming language. And the jar file you are using is just a window into that C world. So it's a rube Goldberg machine. You'll see these sorts of things all over the place in the real work world, so pay attention, you are getting an education here.
Trying to load the library by doing this:
System.loadLibrary("opencv_java244")
Or by doing this:
System.loadLibrary("opencv_java244")
Didn't work - still got the same error.
Finally what worked was providing the full path to the dylib file and using:
System.load(new File("/usr/local/Cellar/opencv/2.4.10.1/share/OpenCV/java/libopencv_java2410.dylib").getAbsolutePath());'
I'm using HomeBrew but however you installed it just find the file and uddate the path.
I find solution. Actual dll is located at openCV\opencv\build\java\x64\ folder. In my case its name is opencv_java247.dll , So i have changed java code line
System.loadLibrary("opencv_java244")
to
System.loadLibrary("opencv_java247")
I also set native library location as E:/Sagar_tools/tools/openCV/opencv/build/java/x64 (full path to dll) in build path.
The function loadlibrary tries to find the name of the the DLL in your PATH variable -- check the DLL name. You can also try System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
In that case, you should give the path for jvm to where the opencv dll file is intalled as : -Djava.library.path="C:\opencv\build\java\x64"
and add the code as :
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
As, i try this in my netbeans ide and my problem is solved.
Hi I am trying to run a project in eclipse and am getting the runtime error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: mywrapperclass.nativemethod()V
I only get the error code when I call a native method in the wrapper class from my main. I have looked around on many forums and blogs/websites and haven't been able to fix this. Debug and my browsing have me led me to thinking that the problem lies in the project not being able to find the native methods within the dll.
I had a lot of trouble getting eclipse to find the .dll and eventually solved this by placing the dll in the system32 folder.
Thanks in advance
Project > Properties > Java Build Path
Click on the arrow of the JAR that needs the DLL library.
Native library location
You have to specify the location of the DLL library.
Easiest way to bundle the dlls with eclipse plugin is
create a folder structure under the plugin like this "os/win32/x86" for x86 architecture and place your dlls there.
and load the libraries like this in your plugin code System.loadLibrary("Dll name");
open .classpath in the project location
Set the dll path as "value" for "CLASSPATH_ATTR_LIBRARY_PATH_ENTRY" attribute
I've been integrating simple java modules into the MATLAB environment on Windows with some success. Recently I encountered a problem with a third-party library which attempts to load a dll.
The java ClassLoader throws the UnsatisfiedLinkError when the load is attempted:
java.lang.UnsatisfiedLinkError: no <libname> in java.library.path
at java.lang.ClassLoader.loadLibrary(Unknown Source)
at java.lang.Runtime.loadLibrary0(Unknown Source)
at java.lang.System.loadLibrary(Unknown Source)
The exception is reporting that my 'libname' is not in the java.library.path property. I have verified that the property does indeed have the correct path in it, and that the libname.dll file exists on that path.
I verified java.library.path in two ways. First, I simply checked that value returned on the MATLAB command line:
>> java.lang.System.getProperty('java.library.path')
Then, I modified the java method in question to print that value just before the call into the failing third-party function:
System.out.println(System.getProperty('java.library.path'));
Both confirmed that my path value was set as expected.
I've also tried manually loading the library from the command line, and it fails with the same results.
Is this something that is not possible in MATLAB, or am I missing something here? Unfortunately I'm not administrator on this machine so I can't try the old trick of moving the dll into a directory with dlls that do work.
I welcome any suggestions for things to try if there is no absolute answer.
Platform:
Windows XP
MATLAB R2009a
Java 1.6
Are you familiar with Process Monitor? (If not you will easily get how it works).
Download it. Run it. Just enable "Show File System Activity" (little icons on right under menu-bar), disable the others.
Then fire up whatever causes the library to try to load the dll. After the UnsatisfiedLinkError occured, stop the event capturing in Process Monitor.
Now do a CTRL+F and search for the name of the dll it should load. Check the (probably multiple) entry which say "Not Found" or "Name not found" in the result column and with the dll-name in the path column.
Now check where it really looks for the dll. Maybe it appends some additional path or similar and thus can't find it.
Just found this in the MATLAB docs:
Specifying the Search Path for Sun Java Native Method DLLs
The mechanism that MATLAB uses to locate native method libraries that are required by Java has changed. MATLAB no longer uses system environment variables to define the paths to these libraries.
Compatibility Considerations
If you presently rely on the PATH (for Windows) or LD_LIBRARY_PATH (for UNIX) environment variables for this purpose, you will need to use the file librarypath.txt, as described below, in its place.
Specifying the Java Library Path
Java classes can dynamically load native methods using the Java method java.lang.System.loadLibrary("LibFile"). In order for the JVM software to locate the specified library file, the directory containing it must be on the Java Library Path. This path is established when MATLAB launches the JVM software at startup, and is based on the contents of the file
$matlab/toolbox/local/librarypath.txt
(where $matlab is the MATLAB root directory represented by the MATLAB keyword matlabroot).
You can augment the search path for native method libraries by editing the librarypath.txt file. Follow these guidelines when editing this file:
Specify each new directory on a line by itself.
Specify only the directory names, not the names of the DLL files. The LoadLibrary call does this for you.
To simplify the specification of directories in cross-platform environments, you can use any of these macros: $matlabroot, $arch, and $jre_home.
Put the DLL that you try to load using java.lang.System.loadLibrary into the following directory:
$matlabroot\sys\java\jre\win??\jre\bin\
Does your library depend on other dlls? It could be that the dll java is loading as a result of its loadLibrary() call requires other dlls. On Windows, I believe it will look on %PATH% to try to find these dlls.
This isn't strictly a java thing; it's more to do with the native library you are loading.
Java is told where to find the dll via java.library.path (or whatever other mechanism Matlab uses), and the libname.dll will use %PATH% to find any dlls it depends on.
As you say that the missing dll is in your java.library.path, perhaps you could try appending the java.library.path value to %PATH% and trying again?