Java – How to fix an UnsatisfiedLinkError (Can’t find dependent libraries) in a JNI project

javajava-native-interfacelibsndfilewindows-xp

I'm working on a Java project that uses the JNI. The JNI calls a custom library that I've written myself, let's say mylib.dll, and that depends on a 3rd party library, libsndfile-1.dll.

When I run my program it crashes with 

java.lang.UnsatisfiedLinkError:  C:\...path...\mylib.dll: Can't find dependent libraries.

I've searched this site (and others) and I've tried a number of fixes:

  1. I ran dependency walker. DW gave a couple of warnings — that two libraries required by libsndfile, MPR.DLL and SHLWAPI.DLL, had "unresolved imports" — but the DW FAQ said that these warnings could be safely ignored.

  2. I fixed the method names in mylib.dll, as suggested here. The method names had somehow gotten mangled by the compiler, but I added linker flags and the dll method names now match those in my jni header file exactly.

  3. I put all of these DLLs in the same directory — the same directory as the .jar that calls them — to ensure that they're on the right PATH.

No dice.

Does anyone have any idea what's going on?

I'm doing my development in Visual Studio 2010 on a MacBook pro (via Parallels). I'm doing my testing in Windows XP on a toshiba laptop.

Best Answer

I'm pretty sure the classpath and the shared library search path have little to do with each other. According to The JNI Book (which admittedly is old), on Windows if you do not use the java.library.path system property, the DLL needs to be in the current working directory or in a directory listed in the Windows PATH environment variable.

Update:

Looks like Oracle has removed the PDF from its website. I've updated the link above to point to an instance of the PDF living at University of Texas - Arlington.

Also, you can also read Oracle's HTML version of the JNI Specification. That lives in the Java 8 section of the Java website and so hopefully will be around for a while.

Update 2:

At least in Java 8 (I haven't checked earlier versions) you can do:

java -XshowSettings:properties -version

to find the shared library search path. Look for the value of the java.library.path property in that output.

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