How to package opencv +java in a jar

Question

I've been using Opencv 2.4.5 with Java for a while building an application and would now like to distribute the app. The library is loaded using the following:

static{ 
        System.loadLibrary("opencv_java245"); 
    }

which works fine. However, when exporting, it doesn't work when running from the jar:

java -jar build1.jar

The opencv_java245.jar file is included as a user library, with a native file (libopencv_java245.dylib) connected to it. When running the executable jar generated from Eclipse, I get the UnsatisfiedLinkError below, despite things compiling/running fine in eclipse.

Exception in thread "main" java.lang.UnsatisfiedLinkError: no opencv_java245 in java.library.path
    at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1860)
    at java.lang.Runtime.loadLibrary0(Runtime.java:845)
    at java.lang.System.loadLibrary(System.java:1084)
    at com.drawbridge.Main.<clinit>(Main.java:12)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:266)
    at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:56)

Anyone know a simple way of packaging OpenCV in the jar?

Update: I have now exhausted everything. I can add the library to my build path (and not use System.loadLibrary) and that works in eclipse, but not when packaged in the jar. I've tried everything. I also checked the type of dynamic library I'm trying to load - it's

Mach-O 64-bit x86_64 dynamically linked shared library

which seems like it should work fine. I've used -D64 and -D32 to test and get the same result with both.

You can't load a native library (or DLL) directly from a JAR. See the linked Question for how to deal with this. — Stephen C
– Stephen C, Commented Aug 16, 2013 at 9:27
Thanks @StephenC I've tried this method and still get UnsatisfiedLinkError but with a different message (something like unknown type). — alistair
– alistair, Commented Sep 12, 2013 at 17:22

Community · Accepted Answer · 2017-05-23 10:31:20Z

11

As Steven C said, it was as in Extract and load DLL from JAR and also in a bug report. I was slightly ignorant of how to use dylibs and was trying to be consistent with an OpenCV tutorial which used a "user library" to add a jar, and then add the native dylib. Also, for some reason loading resources even when using "/" was loading from the src directory, not my project's root directory (which was the case in a test project I made).

For those trying to do the same thing, here's some code to help:

private static void loadLibrary() {
    try {
        InputStream in = null;
        File fileOut = null;
        String osName = System.getProperty("os.name");
        Utils.out.println(Main.class, osName);
        if(osName.startsWith("Windows")){
            int bitness = Integer.parseInt(System.getProperty("sun.arch.data.model"));
            if(bitness == 32){
                Utils.out.println(Main.class, "32 bit detected");
                in = Main.class.getResourceAsStream("/opencv/x86/opencv_java245.dll");
                fileOut = File.createTempFile("lib", ".dll");
            }
            else if (bitness == 64){
                Utils.out.println(Main.class, "64 bit detected");
                in = Main.class.getResourceAsStream("/opencv/x64/opencv_java245.dll");
                fileOut = File.createTempFile("lib", ".dll");
            }
            else{
                Utils.out.println(Main.class, "Unknown bit detected - trying with 32 bit");
                in = Main.class.getResourceAsStream("/opencv/x86/opencv_java245.dll");
                fileOut = File.createTempFile("lib", ".dll");
            }
        }
        else if(osName.equals("Mac OS X")){
            in = Main.class.getResourceAsStream("/opencv/mac/libopencv_java245.dylib");
            fileOut = File.createTempFile("lib", ".dylib");
        }


        OutputStream out = FileUtils.openOutputStream(fileOut);
        IOUtils.copy(in, out);
        in.close();
        out.close();
        System.load(fileOut.toString());
    } catch (Exception e) {
        throw new RuntimeException("Failed to load opencv native library", e);
    }

edited May 23, 2017 at 10:31

CommunityBot

11 silver badge

answered Sep 13, 2013 at 7:23

alistair

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2 Comments

Romantic Electron Over a year ago

What to do if the Operating System is Linux?

alistair Over a year ago

It looks like Linux uses .so files tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html

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