How to fix an UnsatisfiedLinkError (Can't find

问题:

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.

回答1:

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.

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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.

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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.

回答2:

I want to inform this interesting case, after tried all the above method, the error is still there. The weird thing is it works on a Windows 7 computer, but on Windows XP it is not. Then I use dependency walker and found on the Windows XP there is no VC++ Runtime as my dll requirement. After installing VC++ Runtime package here it works like a charm. The thing that disturbed me is it keeps telling Can\'t find dependent libraries, while intuitively the JNI dependent dll is there, however it finally turns out the JNI dependent dll requires another dependent dl. I hope this helps.

回答3:

You need to load your JNI library.

System.loadLibrary loads the DLL from the JVM path (JDK bin path).

If you want to load an explicit file with a path, use System.load()

See also: Difference between System.load() and System.loadLibrary in Java

回答4:

Please verify your library path is right or not. Of course, you can use following code to check your library path path: System.out.println(System.getProperty(\"java.library.path\"));

You can appoint the java.library.path when launching a Java application:

java -Djava.library.path=path ...

回答5:

Did have identical problem with on XP machine when installing javacv and opencv in combination with Eclipse. It turned out that I was missing the following files:

• msvcp100.dll
• msvcr100.dll

Once these were installed, the project compiled and ran OK.

回答6:

If you load a 32 bit version of your dll with a 64 bit JRE you could have this issue. This was my case.

回答7:

I used to have exactly the same problem, and finally it was solved.

I put all the dependent DLLs into the same folder where mylib.dll was stored and make sure the JAVA Compiler could find it (if there is no mylib.dll in the compilation path, there would be an error reporting this during compiling). The important thing you need to notice is you must make sure all the dependent libs are of the same version with mylib.dll, for example if your mylib.dll is release version then you should also put the release version of all its dependent libs there.

Hope this could help others who have encountered the same problem.

回答8:

I had the same issue, and I tried everything what is posted here to fix it but none worked for me. In my case I\'m using Cygwin to compile the dll. It seems that JVM tries to find the JRE DLLs in the virtual Cygwin path. I added the the Cygwin\'s virtual directory path to JRE\'s DLLs and it works now. I did something like:

SET PATH=\"/cygdrive/c/Program Files/Java/jdk1.8.0_45\";%PATH%

回答9:

In my situation, I was trying to run a java web service in Tomcat 7 via a connector in Eclipse. The app ran well when I deployed the war file to an instance of Tomcat 7 on my laptop. The app requires a jdbc type 2 driver for \"IBM DB2 9.5\". For some odd reason the connector in Eclispe could not see or use the paths in the IBM DB2 environment variables, to reach the dll files installed on my laptop as the jcc client. The error message either stated that it failed to find the db2jcct2 dll file or it failed to find the dependent libraries for that dll file. Ultimately, I deleted the connector and rebuilt it. Then it worked properly. I\'m adding this solution here as documentation, because I failed to find this specific solution anywhere else.

回答10:

• Short answer: for \"can\'t find dependent library\" error, check your $PATH (corresponds to bullet point #3 below)
• Long answer:
  1. Pure java world: jvm uses \"Classpath\" to find class files
  2. JNI world (java/native boundary): jvm uses \"java.library.path\" (which defaults to $PATH) to find dlls
  3. pure native world: native code uses $PATH to load other dlls

回答11:

I found a great article by some friends at keepsafe that went through the same thing I did. It worked for me, so hopefully it helps you out as well! Have a read if you\'re interested (The Perils of Loading Native Libraries on Android) or just use

compile \'com.getkeepsafe.relinker:relinker:1.2.3\'

and replace

System.loadLibrary(\"myLibrary\");

with

ReLinker.loadLibrary(context, \"mylibrary\");

回答12:

1. Go to http://tess4j.sourceforge.net/usage.html and click on Visual C++ Redistributable for VS2012
2. Download it and run VSU_4\\vcredist_x64.exe or VSU_4\\vcredist_x84.exe depending upon your system configuration
3. Put your dll files inside the lib folder, along with your other libraries (eg \\lib\\win32-x86\\your dll files).