CODEWITHSUNDEEP
javadlljna
Karloss
Karloss

Reputation: 827

Trying to use DLL from Java (JNA). Unable to load library exception

I have NetBeans project from tutorial which causes exception:

Exception in thread "main" java.lang.UnsatisfiedLinkError: Unable to load library 'simpleDLL': The specified module could not be found.

Tried to put simpleDLL.dll in project libraries, copied file in system32 folder with no success.

Upvotes: 13

Views: 63206

Answers (5)

BackSlash
BackSlash

Reputation: 22243

I had exactly the same problem with loading a DLL, I solved it in this way:

  • As Christian Kuetbach said, check if the simpleDLL you are using is compatible with your processor's architecture, a 32-bit DLL won't work on a 64-bit machine, and also a 64-bit DLL won't work on a 32-bit machine.

  • If the DLL is compatible, then the problem may be in your java library path. I put my DLL into the user.dir directory and then I used this code:

    Set Java library path to user.dir or maybe another path you want:

     String myLibraryPath = System.getProperty("user.dir");//or another absolute or relative path

 System.setProperty("java.library.path", myLibraryPath);

    Load the library:

     System.loadLibrary("libraryWithoutDLLExtension");

It worked for me, try it and tell me if it works for you.

Upvotes: 13

Jefferson Trigueiro
Jefferson Trigueiro

Reputation: 461

Had the same problem and for some reason even if the dll filename has uppercase letters, you have to load it using all lowercase letters like this: Native.loadLibrary("dlls/library.dll", YourInterface.class)

NOT this: Native.loadLibrary("dlls/Library.dll", YourInterface.class)

Upvotes: 0

ZhaoGang
ZhaoGang

Reputation: 4915

Three possible reasons for this issue, if the dll file is not broken:

  1. 32 bit 64 bit Compatibility. 32bit dll can only be running on a 32bit jdk or jre. By using Cygwin command file <filename> we can tell if a dll is 32bit or 64bit.

  2. the dll is not lacated in the right path, so java cannot locate it. Generally speaking we can use some absolut path other than System32 to ensure that the path is right.

  3. the dll that we are loading is requires other dlls.

How can we handle the 3rd possibility:

  1. using JNI's System.loadLibrary() mthod can give me more hint, compared with JNA. It may says something like: Exception in thread "main" java.lang.UnsatisfiedLinkError: MyLibrary.dll: Can't find dependent libraries. It means some libraries MyLibrary.dll depends is missing. By using dependency walker we can tell what dlls are needed.

  2. By loading these dlls before the dll that we want to load, we can solve this issue.

Upvotes: 1

Maur&#237;cio
Maur&#237;cio

Reputation: 21

I could only run in 32bit (Xp).

Place the DLL in the folder "c:\Windows\System32"

helloWorldDLL lib = (helloWorldDLL) Native.loadLibrary("helloworldDLL", helloWorldDLL.class);

If the error java.lang.UnsatisfiedLinkError: Unable to load library" persists, use Dependency Walker to view the dependent DLLs.

Dependency Walker

Upvotes: 2

Christian Kuetbach
Christian Kuetbach

Reputation: 16060

Please check if the simpleDLL is 32 or 64 bit. Then check, if the JVM is also 32 or 64 bit. They have to be for the same platform.

You may also specify an absolute path, if you change loadLibrary() to load(): http://www.chilkatsoft.com/p/p_499.asp

Upvotes: 6

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